Introduction

The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) characterizes a traumatic event as an experience involving actual or threatened death, severe injury, or sexual violence. This exposure can occur in various ways, including direct involvement, witnessing the event, learning that it has happened to a close relative or friend, or repeatedly encountering distressing details related to the event [1]. Throughout history, war and violence have been persistent elements of human existence. Currently, over 65 million people worldwide have been displaced due to armed conflicts, with more than 21 million classified as refugees—over half of whom are under the age of 18. The consequences of war and violence extend beyond societal disruption, profoundly affecting individuals’ lives [2]. Veterans often suffer long-term psychological and physical health challenges following combat exposure, with Post Traumatic Stress Disorder (PTSD) being one of the most prevalent conditions. The impact of war does not only affect the veterans themselves but can also extend to their families [3]. In addition to armed conflict, natural disasters are a significant source of psychological trauma. Research indicates that up to 9% of individuals affected by natural disasters develop PTSD [4]. Other historical traumas, such as the forced displacement of Indigenous children in Canada’s Indian Residential Schools (IRSs) [5], the 1994 genocide against the Tutsi in Rwanda [6], and the institutionalized racial oppression under Apartheid in South Africa [7], have had severe and long-lasting psychological impacts on those who directly experienced them. As the next section will explore, the psychological and social consequences of such traumas often extend beyond the individuals who experienced them firsthand, impacting subsequent generations.

Research studies document that the detrimental effects of trauma can be passed down from one generation of survivors to their children and grandchildren through a phenomenon called intergenerational trauma [8]. The American Psychiatric Association defined “intergenerational trauma” as a situation in which descendants of survivors who have gone through a traumatic incident show similar unfavorable emotional and behavioral responses as those survivors [9]. These responses include feelings of low self-worth, depression, suicidal thoughts, substance abuse, dissociation, hypervigilance, intrusive thoughts, difficulties forming relationships and attachments, difficulties controlling aggression, and extreme reactivity to stress. The impacts of intergenerational trauma are not only manifested in emotional and behavioral responses but also extend to physiological changes. For example, Badel et al. found that maternal PTSD and the age at which mothers were exposed to Holocaust trauma predicted lower cortisol levels in their descendants [10]. Cortisol helps regulate the stress response, and low cortisol levels are associated with a higher predisposition to PTSD. An insufficient cortisol response during or after trauma exposure may fail to contain the stress reaction, leading to over-consolidation of traumatic memories and heightened fear responses, which further increase the risk of developing PTSD [11]. As such, understanding the impacts of intergenerational trauma on second-generation descendants is critical to inform clinical interventions, as well as to develop supportive policies tailored for descendants of trauma survivors.

This systematic review focuses on collective trauma and distinguishes it from individual trauma. Collective trauma refers to the psychological impact experienced by a group of people because of traumatic events, such as natural disasters, genocide, war, or pandemics. This form of trauma is associated with the collective’s shared experiences and emotional reactions and is closely linked to the social and cultural environment of the affected group [12]. In contrast, individual trauma arises from events that directly affect a single person, such as accidents, assaults, or family violence. Its effects are closely related to the circumstances and personal history of the individual who experiences them [13]. This review centers on collective trauma because it affects not only individuals but also entire communities. When a group experiences traumatic events, such as war, genocide, or displacement, the impact can be felt across generations. Collective trauma shapes how people see themselves, relate to others, and how society functions. Unlike individual trauma, collective trauma is distinguished by its broader social scope, its potential to influence cultural values and norms, and the interconnectedness of individual identities within the collective [14]. Understanding collective trauma is essential for developing healing strategies that reach beyond individual therapy to include education, public policy, and community-based support.

This systematic review focuses on the impacts of survivors’ trauma on second-generation descendants, distinguishing them from third-generation descendants, as the effects of trauma are notably different between the two generations. A meta-analysis conducted by Sagi-Schwartz et al. did not find any evidence of tertiary traumatization in the third generation of Holocaust survivors [15]. This study revealed that the third generation does not exhibit inferior outcomes compared to established norms or control groups in many areas, such as general adjustment, aggression, internalizing behaviors, attachment, and other psychological characteristics. Moreover, research conducted in communities has revealed lessened effects of intergenerational trauma across generations, with reduced consequences on the third generation [16].

A robust literature encompassing quantitative studies investigates the impacts of intergenerational collective trauma on second-generation descendants in various contexts, including descendants of survivors of the Holocaust, genocide, war invasions, displacement, and natural disasters. However, these studies present contradictory findings regarding whether intergenerational collective trauma directly impacts the psychological well-being of second-generation descendants. In other words, some of these studies document that trauma experienced by survivors has an impact on their descendants, while other studies refute this conclusion. For instance, Gangi et al. found that adult children of Holocaust survivors had significantly higher levels of anxiety, lower levels of self-esteem, and lower levels of inhibition of aggression compared to adult children of non-Holocaust survivors [17]. Additionally, in their study, Kim et al. found that the offspring of mothers, who experienced more significant levels of trauma during the South African Apartheid, displayed elevated psychiatric problems during late adolescence [7]. On the other hand, some studies have documented that the impacts of intergenerational trauma do not transmit from one generation to the next. For instance, Muhtz et al. found that the mental health and quality of life of adult children of parents with chronic PTSD did not significantly differ from those whose parents did not have PTSD [18]. Finally, Ingabire et al. found that there was no significant relation between both mothers’ trauma exposure and PTSD symptoms and their adult offspring’s depression or PTSD symptoms [6]. As such, it is important to systematically analyze the findings of these quantitative studies while considering their methodological limitations, including sample size, sample characteristics, study design (e.g., cross-sectional vs. longitudinal), and control of potential confounding variables.

On the other hand, while a substantial body of literature has examined the impacts of intergenerational collective trauma on second-generation descendants, the existing evidence remains scattered across various disciplines and marked by considerable variation in research designs and methodologies. Moreover, there is a relative lack of systematic reviews that synthesize these findings. To date, the literature includes one systematic review and two meta-analyses focused specifically on intergenerational collective trauma resulting from war and the Holocaust. However, no systematic reviews have been published that encompass all types of collective trauma or provide a comprehensive overview of associated outcomes. Sangalang et al. conducted a systematic review on the on the intergenerational impacts of war-related trauma among second-generation descendants of refugee families [19]. Moreover, two meta-analyses, by Payne et al. [20] and Van IJzendoorn and Sagi-Schwartz [21], examined whether children of Holocaust survivors were more likely to develop PTSD and whether they exhibited poorer adaptation, respectively. This systematic review is therefore essential to bridge existing gaps by providing a comprehensive synthesis of the diverse and fragmented body of research on intergenerational collective trauma, encompassing a broader range of trauma types and descendants’ outcomes beyond those previously explored.

In conclusion, this review examines the impacts of various forms of intergenerational collective trauma, including genocide, the Holocaust, war, historical trauma, and natural disasters, to address the research question: What are the effects of intergenerational collective trauma on the physiological and psychological outcomes of second-generation descendants? Additionally, the review discusses the limitations of the studies analysed and provides recommendations for future research to deepen our understanding of intergenerational trauma and its effects on subsequent generations.

Methodology

A systematic literature search was conducted between June and December 2023, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [22], to identify studies on intergenerational trauma in second-generation descendants published over the past 25 years, from 1997 to 2022. This time frame was selected to balance historical depth with the inclusion of contemporary findings relevant to the evolving understanding of intergenerational trauma. We identified articles through PsychInfo (EBSCO), PsychArticles (EBSCO), Medline (EBSCO), Web of Science Core Collection (Thompson Routers), Embase (Elsevier), and PubMed (National Center for Biotechnology Information) to combine the following keywords: intergenerational trauma, transgenerational trauma, historical trauma, secondary traumatization, and collective trauma. Figure 1 contains a flowchart of the study selection. The studies were considered eligible for inclusion if they: (a) investigated the impact of intergenerational trauma (that was collective) across second-generation descendants of survivors; (b) used quantitative methodology; (c) and published in English in peer-reviewed journals. Excluded were studies (d) based solely on a review of the literature (conceptual) with no data collection; (e) implemented a qualitative methodology of data collection; (f) implemented single case clinical study design of data collection; (g) included the study of the impact of intergenerational trauma on the third-generation descendants; (h) studied personal trauma (that is not collective) such as maternal maltreatment during childhood. Exclusion of studies based on the type of collective intergenerational trauma (holocaust, civil war, genocide, etc.) or the geographical location did not occur.

In the initial search, 3904 studies were retrieved. After excluding duplicates, 1721 studies remained. Next, two researchers independently reviewed the titles and abstracts. After screening the abstracts, 93 articles remained and based on the full text, the final selection consisted of 18 studies. Regarding data extraction, the accuracy of the article extraction was reviewed by two independent authors, and any discrepancies were resolved through discussion until consensus was achieved on all studies. The two reviewers independently screened and extracted data from the 18 included studies.

Results

The final selection of studies encompasses studies that focused on the intergenerational impact of trauma on second-generation descendants. Studies that were reviews or qualitative, not specific to collective trauma, and focused on the effects of the trauma on third-generation descendants did not meet the inclusion criteria and, therefore, could not be included. The CASP quality assessment tool was used to evaluate the quality of the reviewed studies, addressing 11 specific domains: (1) stating a focused issue; (2) use of appropriate methods; (3) acceptable recruitment strategies; (4) accurate, validated measures to reduce bias; (5) data collection strategies; (6) sufficient number of participants to minimize chance; (7) presentation of results; (8) sufficiently rigorous data analysis; (9) clear statement of findings; (10) applicability to the local population; and (11) value of the research conducted [23]. Two authors independently applied the CASP tool to each included study, documenting supporting information and justifications for their risk of bias judgments. Any discrepancies in assessments or justifications were resolved through discussion until a consensus was reached. The assessment revealed that most studies met the criteria for items 1, 2, 5, 7, 8, and 9. However, shortcomings were observed in items 3, 4, 6, 10, and 11. Specifically, some studies could not implement optimal recruitment methods and had to rely on alternative approaches. Others used measures that were not standardized or did not accurately capture the intended variables. Several studies had small sample sizes, often due to the nature of the trauma being studied. Most studies lacked generalizability to the local population, and many provided only preliminary insights rather than conclusive evidence. Nevertheless, the 18 studies were included to conduct this systematic review, as they were appropriate and relevant enough in terms of research objective, data collection and implications.

Overview of study characteristics and emergent themes

The study characteristics of the selected studies are presented in Table 1. Our review included 18 studies, all of which utilized quantitative methods. Eight studies utilized a parent-child dyadic design, recruiting one or both parents and their descendants to collect data on the trauma experienced by the survivor parents and its direct impacts on the physiological and psychological outcomes in their descendants. Ten studies used comparative analyses to compare two or more groups of descendants, such as those who are offspring of trauma survivors and those who are not, focusing on differences on physiological and psychological outcomes. The themes that emerged from our analysis highlight the impacts of intergenerational trauma on: (a) epigenetics and physiological outcomes; (b) interpersonal relationships and social identity; and (c) psychological distress and psychopathology.

Impacts of intergenerational trauma on the epigenetics and physiology of descendants

Three studies explored the epigenetic and physiological impacts of intergenerational trauma on descendants. These studies consistently demonstrated the effects of intergenerational trauma on both epigenetic and physiological outcomes in descendants. Yehuda et al. [24] and Bader et al. [10] found that offspring of Holocaust survivors with parental PTSD exhibited reduced Glucocorticoid receptor gene exon 1 F promoter region (GR-1 F) gene methylation and lower cortisol levels, respectively, while Sarigedik et al. [4] showed that children of mothers exposed to an earthquake had smaller bilateral amygdala volumes. Yehuda et al. studied Holocaust Survivor Offspring (HSOs) and Non-Holocaust Survivor Offspring (NHSOs) (N = 80 HSOs; N = 15 NHSOs) and found that reduced methylation of the GR-1 F gene promoter was associated with both maternal and paternal PTSD, with maternal PTSD moderating paternal effects; the lowest methylation levels were seen in offspring of two PTSD-affected parents, suggesting heightened vulnerability to stress via impaired glucocorticoid regulation [24]. Bader et al., comparing N = 69 HSOs and N = 26 controls, found that maternal PTSD and the age at which mothers experienced Holocaust trauma predicted lower urinary cortisol levels and greater PTSD symptoms in offspring; effects stronger than those of the offspring’s own trauma exposure [10]. Finally, Sarigedik et al. compared N = 40 children of earthquake-exposed mothers with N = 27 controls in Turkey and found significantly smaller bilateral amygdala volumes in the trauma group. Children of mothers exposed during adolescence had larger left amygdala and hippocampal volumes compared to their right counterparts; though no significant differences in hippocampal volumes were observed between the two groups [4].

Impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity

Three studies explored the impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity. These studies consistently demonstrated the effects of intergenerational trauma on both areas. Gangi et al. [10] found that HSOs showed higher anxiety, avoidance, and defensiveness compared to controls. Sorcher & Cohen [25] observed more Holocaust-related imagery in HSOs, but no difference in Jewish identity. Ingabire et al. [6] found that mothers’ PTSD symptoms negatively influenced their children’s attitudes toward reconciliation. Gangi et al. [10] studied the impact of Holocaust intergenerational trauma on second-generation descendants using a comparative design with 40 HSOs and 37 Italian Jewish controls (NHSOs). They found that HSOs exhibited more avoidance of interpersonal conflicts, competitions, caution, submissiveness, yielded to others and worry about personal relationships, along with less expressiveness and more defensiveness in response to depressive feelings. HSOs also had higher anxiety levels than NHSOs, perceived themselves as less-sufficient and assertive, and perceived their families as less emotionally expressive and more focused on responsibility, morality, and religious values. Finally, in comparison to their actual families, HSOs described the ideal family as more accepting to challenges and more oriented toward competition, compared to NHSOs [10]. Sorcher & Cohen [25] compared 40 HSOs and 38 NHSOs descendants. HSOs had significantly higher levels of Holocaust-related imagery, including thoughts, dreams, and memories of related places, but no significant difference was found in overall Jewish identity between the two groups. HSOs also reported higher levels of loyalty [25]. Finally, Ingabire et al. [6] examined intergenerational trauma from the 1994 Rwandan genocide with 181 mother-child dyads. The study found that mothers’ PTSD symptoms were negatively associated with their adult children’s attitudes toward reconciliation, indicating a link between parental mental health and second-generation attitudes in post-conflict societies. However, there was no direct association between mothers’ attitudes toward reconciliation and those of their offspring, suggesting that the negative attitudes were driven by witnessing their mothers’ psychological distress rather than mimicking their views [6].

Impacts of intergenerational trauma on descendants’ psychological distress and psychopathology

Thirteen studies examined the impact of intergenerational trauma on descendants’ psychological distress and psychopathology. They were categorized by trauma type: three focused on war-related trauma in veterans’ families, two on war-related trauma in refugees, five on genocide, and three on the Holocaust, apartheid, and residential schools.

War veterans’ families

Three studies explored the impact of intergenerational trauma on descendants’ psychological distress and psychopathology in war veterans’ families. Two studies, Castro-Vale et al. [26] and O’Toole et al. [3], consistently demonstrated effects in both areas, while Wasterink and Giarratano [27] did not find such effects, likely due to the small sample size.

Castro-Vale et al. [26] examined intergenerational trauma in 46 Portuguese war veterans, 44 adult children of veterans with PTSD, and 29 of those without. Some families contributed multiple children. Veterans’ trauma exposure was linked to their children’s phobic anxiety, somatization, overall psychological distress, and symptom intensity. However, fathers’ lifetime PTSD was not associated with descendants’ attachment styles, psychopathology, or childhood maltreatment. The authors suggest that higher educational attainment among children may have helped them cope with their fathers’ PTSD, though they were still affected by its emotional burden [26].

O’Toole et al. [3] and Wasterink and Giarratano [27] both investigated the intergenerational effects of Vietnam War trauma on veterans’ children but reported differing outcomes, largely due to sample size. O’Toole et al., using a large sample of 315 descendants, found significantly higher trauma exposure, PTSD, and mental health issues among veterans’ children compared to matched controls, despite stable family environments. Gender differences emerged, with daughters experiencing more trauma and PTSD, and sons exhibiting higher substance use [3]. In contrast, Wasterink and Giarratano studied a smaller sample of 21 children of veterans with PTSD and 14 controls. While children of veterans reported increased familial conflict, no significant differences were found in self-esteem or psychological distress. The authors acknowledged the limited sample size as a key constraint, suggesting their findings should be viewed as preliminary [27].

War refugees

Vaage et al. [28] and Muhtz et al. [18] both examined intergenerational trauma among refugee families. Both studies showed that intergenerational trauma among refugees impact the psychological distress and psychopathology of descendants. Vaage et al. examined intergenerational trauma in 88 Vietnamese refugee parents, 12 adult children (aged 19–23 years), and 94 children (aged 4–18 years) resettled in Norway, with data collected at arrival (1982, T1), follow-up (1985, T2), and 23 years later (T3). T3 findings showed that paternal, but not maternal, psychological distress was significantly associated with second-generation distress, possibly due to strong father-child bonds in South Asian cultures. PTSD at T1 predicted mental health problems in descendants at T3, though overall parental trauma at T1 did not. Despite 30% of fathers having PTSD, descendants were more resilient than Norwegian peers [28]. Muhtz et al. studied 25 s-generation descendants of WWII refugees with PTSD and 25 without, all from former eastern German territories. They found that perceived burden from parental trauma, not PTSD diagnosis, was linked to poorer mental health and quality of life, especially in areas like pain, physical functioning, and emotional wellbeing. No significant differences were found between children of PTSD and non-PTSD parents when compared as distinct groups. These findings suggest that the intergenerational impact of trauma may be shaped more by how the trauma is emotionally experienced and interpreted by the next generation than by the presence of parental PTSD alone [18].

Apartheid, residential school, and holocaust

Although Kim et al. [7] Bombay et al. [5] and Yehuda et al. [29] investigated the intergenerational impacts of three distinct traumas; South African Apartheid, Indian Residential Schools (IRS), and the Holocaust, their findings converge on key psychological outcomes in second-generation descendants. Kim et al. [7] investigated the impact of trauma during South African Apartheid in a sample of 304 mother-adolescent dyads drawn from the largest and longest-running longitudinal birth cohort study on child development and health in Africa. Their results showed that adolescents whose mothers experienced higher levels of trauma during Apartheid displayed increased psychiatric morbidity in late adolescence, 17 to 18 years after the exposure to prenatal stress, highlighting the lasting intergenerational effects of maternal trauma. Similarly, Bombay et al. [5] examined the intergenerational impact of trauma associated with the Indian Residential School (IRS) system by comparing second-generation descendants of IRS survivors (N = 67) with those whose parents had not attended IRS (N = 76). The study found that descendants of IRS survivors experienced higher levels of depressive symptoms, greater exposure to adverse childhood experiences, adult trauma, and discrimination, despite having comparable levels of education and income to the comparison group. Finally, Yehuda et al. [29] examined the psychiatric outcomes of HSOs compared to NHSOs in the U.S. HSOs showed higher levels of depression, anxiety, and, to a lesser extent, substance use disorders. While PTSD rates did not differ overall between groups, maternal PTSD was consistently associated with offspring PTSD, regardless of paternal PTSD status. Both maternal and paternal PTSD were linked to increased depression in offspring. Anxiety was more common among all HSOs, regardless of parental PTSD. Paternal PTSD influenced offspring PTSD only when maternal PTSD was also present, whereas maternal PTSD had a stronger and independent effect, amplified by the presence of paternal PTSD.

Genocide

Three studies have explored the intergenerational transmission of trauma stemming from the Cambodian genocide, revealing both converging and diverging findings. Field et al. [30] using a sample of 200 high school students, found that adolescents’ levels of anxiety and depression were positively associated with their perceptions of both paternal and maternal trauma exposure and symptoms. Similarly, Shrira et al. [31] in a study involving 60 parent-child dyads, reported that parental PTSD and Complex PTSD were linked to greater secondary traumatization and reduced resilience among second-generation descendants. They also found that parental resilience was positively correlated with increased resilience in their children, suggesting a potential buffering effect. In contrast, Burchert et al. [32] analyzing data from 378 Cambodian mother-child dyads, found no significant association between maternal PTSD/PTSS (Post Traumatic Stress Symptoms) and the PTSD/PTSS symptoms of their children. This divergence may be attributed to differences in measured outcomes: while Field and Shrira focused on broader psychological effects such as anxiety, depression, and resilience, Burchert et al. specifically assessed trauma-related symptoms (PTSD/PTSS) and found no direct transmission. This suggests that while parental trauma may influence general emotional well-being and coping capacity in children, it may not always manifest in trauma-specific disorders, underscoring the importance of distinguishing between different psychological outcomes when studying intergenerational trauma.

Roth et al. [33] and Ingabire et al. [6] both examined intergenerational trauma stemming from the 1994 Rwandan genocide in mother-child dyads (N = 125 and N = 181, respectively). Both studies found no significant association between maternal trauma exposure or PTSD and their children’s psychological symptoms, general psychological issues in Roth et al., and PTSD and depression in Ingabire et al., after accounting for the child’s own trauma. However, Roth et al. observed that children’s psychological problems were significantly associated with maternal perpetration of domestic violence, which was itself linked to the mothers’ own childhood exposure to violence rather than their PTSD symptoms [33]. Ingabire et al. further emphasized that maternal PTSD was unrelated to adult offspring’s mental health but previously found it influenced their attitudes toward reconciliation. Both studies highlight a key limitation, notably the lack of data on paternal mental health, which may play a crucial role in shaping intergenerational outcomes [6].

Discussion

This review aimed to investigate the impacts of intergenerational trauma on second-generation descendants. We conducted a systematic literature search and included 18 quantitative studies, published between January 1997 and December 2022, that examined the intergenerational impact of trauma on second-generation descendants. Studies focusing on third-generation effects, qualitative or review-based approaches, or non-collective designs were excluded. The CASP quality assessment revealed that while most studies had clear aims, rigorous analyses, and reliable data collection, limitations were noted in recruitment methods, measurement validity, sample size, generalizability, and practical applicability. Despite these limitations, all included studies were deemed sufficiently relevant to the research objectives. The reviewed studies employed either a parent-child dyadic design or comparative group analyses. Three central themes emerged across studies: (a) epigenetic and physiological outcomes; (b) interpersonal relationships and social identity; and (c) psychological distress and psychopathology; highlighting the multifaceted and enduring impacts of intergenerational trauma.

Parental trauma and descendants’ physiological changes

Emerging evidence highlights the physiological and epigenetic consequences of intergenerational trauma. Three studies consistently demonstrate that trauma exposure in parents can alter stress-related biological systems in their offspring. Yehuda et al. and Bader et al. documented that offspring of Holocaust survivors with parental PTSD showed reduced GR-1 F gene methylation [24] and lower cortisol levels [10], respectively, markers of impaired glucocorticoid regulation and heightened stress sensitivity. Reduced methylation of the GR-1 F gene leads to increased expression of glucocorticoid receptors. This means the body becomes more sensitive to cortisol. As a result, the negative feedback loop in the Hypothalamic Pituitary Adrenal (HPA) axis becomes more active, leading to reduced production of cortisol after stress [24, 34]. Cortisol plays a crucial role in regulating the stress response and modulating memory consolidation, particularly in relation to traumatic events, with lower levels being associated with heightened vulnerability to PTSD. When the cortisol response is insufficient during or after trauma, it may fail to adequately contain the stress reaction, resulting in the over-consolidation of traumatic memories and increased fear responses. Additionally, low cortisol levels can impair the body’s ability to effectively shut down the stress response, contributing to chronic hyperarousal and heightened anxiety commonly observed in post-traumatic stress disorder [35,36,37]. Similarly, Sarigedik et al. found that children of earthquake-exposed mothers had significantly smaller amygdala volumes, with developmental timing of maternal trauma influencing neural outcomes [4]. The amygdala region is central to processing emotions such as fear and threat detection. A reduced amygdala volume has been associated with impaired emotional regulation and an overactive stress response, characterized by heightened reactivity to perceived threats even in non-threatening environments. This dysregulation may increase vulnerability to psychological disorders, including post-traumatic stress disorder (PTSD) [38, 39].

Impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity

Intergenerational trauma appears to shape both interpersonal relationships and social identity in descendants. Gangi et al. found that offspring of trauma survivors have been found to exhibit heightened anxiety, avoidance, and interpersonal defensiveness, along with perceptions of their families as less emotionally expressive and more morally rigid [10]. Sorcher & Cohen also reported that descendants exhibited increased trauma-related imagery and a stronger sense of loyalty, despite no significant changes in broader identity markers [25]. In other contexts, such as post-genocide societies, Ingabire et al. found that parental PTSD symptoms have been linked to more negative attitudes toward reconciliation among descendants, likely shaped by witnessing psychological distress rather than directly adopting parental views [6]. These findings suggest that parental trauma can subtly influence how descendants relate to others and construct their social identities. This is consistent with existing research on the effects of the Holocaust and genocide, which shows that intergenerational trauma can have a significant impact on feelings of mistrust and fear toward others [39, 40].

Impacts of intergenerational trauma on descendants’ psychological distress and psychopathology

The impact of intergenerational trauma on descendants’ psychological distress and psychopathology has been widely explored across various trauma types, including war-related trauma, genocide, and experiences related to the Holocaust, apartheid, and residential schools. These studies collectively highlight significant psychological consequences for descendants, although the findings vary based on the specific type of trauma.

In the context of war veterans’ families, several studies have shown that the trauma experienced by veterans, particularly those with PTSD, significantly affects their children. For instance, Castro-Vale et al. [26] found that children of veterans with PTSD exhibited increased psychological distress, including phobic anxiety and somatization. Similarly, O’Toole et al. [3] observed heightened levels of PTSD and trauma exposure among children of Vietnam War veterans. However, Wasterink and Giarratano [27] found no significant psychological distress in children of veterans, a result they attributed to the small sample size. Overall, the studies on war veterans’ families consistently show that the psychological toll of war extends beyond the combatants themselves, affecting the emotional wellbeing of the next generation.

The studies on war refugees further emphasize the enduring effects of intergenerational trauma on descendants. Both Vaage et al. [28] and Muhtz et al. [18] found that the trauma experienced by refugee parents, particularly those with PTSD, had a profound impact on their children’s mental health. Vaage et al. highlighted that paternal trauma was particularly influential on second-generation distress, likely due to the strong father-child bond in many cultures. In contrast, Muhtz et al. noted that the emotional burden perceived by children, rather than the presence of PTSD in parents, was a stronger predictor of poor mental health outcomes in the next generation. These findings suggest that the emotional interpretation and perceived burden of trauma by descendants may play a more significant role in shaping their psychological distress than the mere presence of PTSD in parents.

The studies on the Holocaust, apartheid, and residential schools also reveal notable psychological outcomes in descendants. Kim et al. [7] found that adolescents whose mothers experienced high levels of trauma during apartheid showed increased psychiatric morbidity, highlighting the lasting effects of maternal trauma. Similarly, Bombay et al. [5] reported that descendants of Indian Residential School survivors exhibited more depressive symptoms and adverse childhood experiences. Yehuda et al. [29] found that Holocaust survivor offspring experienced higher levels of depression and anxiety, with maternal PTSD being a particularly strong factor in the transmission of these symptoms.

Studies on the intergenerational transmission of trauma following the Cambodian and Rwandan genocides present a complex and nuanced picture. Research on the Cambodian genocide indicates partial transmission of trauma-related effects across generations, though findings vary depending on the psychological outcomes assessed. Field et al. [30] and Shrira et al. [31] found that parental trauma, especially PTSD and Complex PTSD, was linked to heightened anxiety, depression, and reduced resilience in children, with parental resilience serving a potential protective function. In contrast, Burchert et al. [32] found no direct association between maternal PTSD/PTSS and similar symptoms in offspring, suggesting that trauma may influence broader emotional well-being without necessarily resulting in diagnosable trauma-specific disorders. These discrepancies highlight the importance of distinguishing between general psychological distress and clinical trauma symptoms when assessing intergenerational impacts. Similarly, studies on the Rwandan genocide (Roth et al. [33]; Ingabire et al. [6]) found no significant direct link between maternal trauma or PTSD and the psychological symptoms of their children, once the child’s own trauma exposure was considered. However, Roth et al. noted an indirect pathway, where maternal experiences of childhood violence, rather than their PTSD, were associated with both perpetration of domestic violence and their children’s psychological difficulties. Ingabire et al. also highlighted that maternal PTSD influenced offspring’s reconciliation attitudes, pointing to more subtle, value-based transmissions. It is conceivable that the way a society responds after genocide significantly influences how trauma is passed down through generations. In Rwanda, timely initiatives focused on recognition, justice, and reconciliation have contributed to reducing the transmission of trauma to descendants [41]. Meanwhile, Cambodia’s slower and less comprehensive approach has likely intensified the intergenerational effects of trauma, worsened by ongoing silence and insufficient mental health support [42].

Methodological issues

This study’s strength lies in its systematic analysis of all empirical studies on intergenerational trauma published over the past 25 years. We evaluated a range of factors that were only partially addressed in previous reviews. However, despite focusing solely on quantitative research, our findings highlight significant heterogeneity in sample types and measurement instruments across studies making direct comparisons and drawing unified conclusions. Moreover, only a small number of researchers have investigated intergenerational trauma, and many studies had findings that were not widely generalizable, requiring cautious interpretation. Furthermore, the nature of collective trauma itself may influence its intergenerational effects differently, emphasizing the need to examine specific trauma types separately, rather than assuming a uniform mechanism of transmission. Studies predominantly relied on cross-sectional designs which impede the ability to draw causal inferences about the impact of intergenerational trauma. Longitudinal studies are crucial for identifying causal pathways and understanding how intergenerational trauma evolves [43, 44]. Furthermore, small sample sizes in several dyadic and comparative studies undermine the statistical power and generalizability of their findings, making it difficult to extend conclusions beyond the studied populations [45, 46]. The studies also failed to account for parental exposure to other forms of trauma and confounding variables potentially skewing the observed associations. The exclusive recruitment from non-clinical settings may also lead to an underestimation of the clinical significance of intergenerational trauma [6]. Lastly, the reliance on self-report measures, where some were not standardized, raises concerns about the validity of the reported psychopathology [47].

Recommendations for clinical practice

This systematic review sought to answer the research question: Does intergenerational collective trauma impact the physiological and psychological outcomes of second-generation descendants? The evidence synthesized from 18 quantitative studies strongly supports the notion that intergenerational trauma can profoundly affect second-generation descendants across multiple domains. Physiologically, trauma-related changes in stress regulation systems and brain structures were observed, suggesting biological embedding of trauma across generations. Socially and relationally, intergenerational trauma shaped interpersonal dynamics and influenced social identity formation, often fostering mistrust, emotional restraint, and heightened moral rigidity. Psychologically, descendants exhibited heightened levels of distress, anxiety, depression, and trauma-related symptoms, with parental PTSD emerging as a significant predictor.

To address intergenerational trauma effectively, a multifaceted approach is required, incorporating therapeutic interventions and community initiatives. Emerging physiological and epigenetic evidence; such as reduced cortisol levels, altered glucocorticoid receptor gene methylation, and smaller amygdala volumes, suggests that descendants of trauma survivors may have heightened biological sensitivity to stress and impaired emotional regulation. These findings underscore the need for trauma interventions that are not only psychologically informed but also biologically attuned. Recent studies examining the impact of trauma-focused psychotherapy, including Trauma Focused- Cognitive Behavior Therapy and EMDR (Eye Movement Desensitization and Reprocessing), have begun to show promise in reversing some of these biological effects, such as normalizing stress hormone levels and modulating epigenetic markers [48, 49]. As such, therapeutically, mental health professionals should integrate such interventions that address the epigentic and physiological imprints of intergenerational trauma and support regulation of the stress response. Addditionally, early screening for heightened biological stress sensitivity—even in individuals without direct trauma exposure—can inform personalized treatment planning. This is especially relevant for populations with intergenerational trauma histories, where inherited physiological vulnerabilities may not be immediately visible but still significantly influence mental health outcomes. Mental health practitioners must also develop a comprehensive understanding of the cultural and historical contexts that shape the transmission of intergenerational trauma and its effects on second-generation descendants. A trauma-informed care framework is crucial, recognizing the profound impact trauma has on a descendant’s well-being. Mental health professionals are encouraged to proactively assess exposure to intergenerational trauma during the trauma narrative evaluation, ensuring that therapeutic interventions are tailored to the ways in which intergenerational trauma influences an individual’s psychological well-being, social identity, and potential psychopathological development. Moreover, this approach necessitates that family therapists examine intergenerational patterns of behavior and communication, which may perpetuate the cycle of trauma. At the community level, psychoeducation and awareness campaigns can play a significant role in improving understanding of intergenerational trauma, empowering communities to adopt effective strategies to mitigate its impact. Finally, advocating for policies that address the root causes of trauma, such as poverty, inequality, and systemic violence, is essential to this comprehensive effort.

Introduction

A traumatic event is defined by the DSM-5 as an experience involving actual or threatened death, serious injury, or sexual violence. Exposure to such events can occur directly, by witnessing the event, by learning it happened to a close relative or friend, or by repeatedly encountering distressing details of the event. Throughout history, war and violence have been constant features of human existence. Currently, over 65 million people globally have been displaced by armed conflicts, with more than 21 million categorized as refugees. The effects of war and violence extend beyond societal disruption, deeply impacting individual lives. Veterans often face long-term psychological and physical health issues after combat, with Post-Traumatic Stress Disorder (PTSD) being common. The consequences of war can also affect veterans' families. Additionally, natural disasters are a major cause of psychological trauma; research indicates that up to 9% of individuals affected by such disasters develop PTSD. Other historical traumas, such as the forced displacement of Indigenous children in Canada's Indian Residential Schools, the 1994 genocide against the Tutsi in Rwanda, and institutionalized racial oppression under Apartheid in South Africa, have led to severe and lasting psychological effects on direct survivors.

Research shows that the harmful effects of trauma can be passed down from one generation of survivors to their children and grandchildren, a phenomenon known as intergenerational trauma. The American Psychiatric Association defines intergenerational trauma as a situation where descendants of trauma survivors display similar negative emotional and behavioral responses as the survivors themselves. These responses include low self-worth, depression, suicidal thoughts, substance use, dissociation, hypervigilance, intrusive thoughts, difficulties with relationships, problems controlling aggression, and extreme reactions to stress. The impacts of intergenerational trauma also include physiological changes. For instance, studies have found that maternal PTSD and the mother's age at the time of Holocaust trauma predicted lower cortisol levels in their descendants. Cortisol helps regulate the stress response; low cortisol levels are linked to a higher risk of PTSD. An inadequate cortisol response during or after trauma may fail to control the stress reaction, leading to stronger traumatic memories and heightened fear, which further increases the risk of developing PTSD. Therefore, understanding the effects of intergenerational trauma on second-generation descendants is crucial for clinical treatments and supportive policies.

This review focuses on collective trauma, distinguishing it from individual trauma. Collective trauma refers to the psychological impact a group experiences from traumatic events such as natural disasters, genocide, war, or pandemics. This form of trauma is linked to shared experiences and emotional reactions within the group, and it is closely tied to the social and cultural environment. In contrast, individual trauma comes from events that directly affect one person, like accidents, assaults, or family violence. Its effects are related to the circumstances and personal history of the individual. This review centers on collective trauma because its effects impact not only individuals but entire communities and can span generations, shaping self-perception, relationships, and societal function. Collective trauma is unique due to its wider social scope, its potential to influence cultural values, and the interconnectedness of individual identities within the group. Understanding collective trauma is vital for developing healing strategies that extend beyond individual therapy to include education, public policy, and community support.

This systematic review specifically examines the effects of survivors' trauma on second-generation descendants, distinguishing them from third-generation descendants, as the effects of trauma vary between these generations. A meta-analysis did not find evidence of tertiary traumatization in the third generation of Holocaust survivors. This study showed that the third generation generally did not exhibit poorer outcomes in areas such as general adjustment, aggression, internalizing behaviors, attachment, or other psychological characteristics compared to established norms or control groups. Moreover, community research has indicated lessened effects of intergenerational trauma across generations, with reduced consequences observed in the third generation.

A large body of quantitative research investigates the impacts of intergenerational collective trauma on second-generation descendants in various contexts, including those descended from survivors of the Holocaust, genocide, war, displacement, and natural disasters. However, these studies present conflicting findings regarding whether intergenerational collective trauma directly affects the psychological well-being of second-generation descendants. Some studies report that survivors' trauma impacts their descendants, while others dispute this. For example, some researchers found that adult children of Holocaust survivors had significantly higher anxiety, lower self-esteem, and less inhibition of aggression compared to those without Holocaust survivor parents. Additionally, offspring of mothers who experienced severe trauma during South African Apartheid showed elevated psychiatric problems in late adolescence. Conversely, some studies have found that intergenerational trauma impacts do not transmit across generations. For instance, one study found that the mental health and quality of life of adult children of parents with chronic PTSD did not significantly differ from those whose parents did not have PTSD. Another study found no significant link between mothers' trauma exposure and PTSD symptoms and their adult offspring's depression or PTSD symptoms. Therefore, a systematic analysis of these quantitative studies, considering methodological limitations such as sample size, characteristics, study design, and control of confounding variables, is important.

While significant literature exists on the impacts of intergenerational collective trauma on second-generation descendants, the evidence is spread across disciplines with varied research designs and methods. There is a relative lack of systematic reviews that synthesize these findings. Currently, the literature includes one systematic review and two meta-analyses focused specifically on intergenerational collective trauma from war and the Holocaust. However, no systematic reviews have been published that cover all types of collective trauma or offer a broad overview of associated outcomes. A systematic review examined the intergenerational impacts of war-related trauma among second-generation descendants of refugee families. Additionally, two meta-analyses investigated whether children of Holocaust survivors were more likely to develop PTSD and whether they showed poorer adaptation. This systematic review is thus essential to fill existing gaps by comprehensively synthesizing the diverse and fragmented research on intergenerational collective trauma, including a wider range of trauma types and descendant outcomes than previously explored. This review will examine the impacts of various forms of intergenerational collective trauma, including genocide, the Holocaust, war, historical trauma, and natural disasters. The research question for this study is: What are the effects of intergenerational collective trauma on the physiological and psychological outcomes of second-generation descendants? Additionally, the review discusses the limitations of the analyzed studies and offers recommendations for future research to enhance understanding of intergenerational trauma and its effects on subsequent generations.

Methodology

A systematic literature search was conducted between June and December 2023, following established guidelines for systematic reviews. The search aimed to identify studies on intergenerational trauma in second-generation descendants published over the past 25 years, from 1997 to 2022. This timeframe was chosen to balance historical context with current research on intergenerational trauma. Articles were identified through several databases, including PsychInfo, PsychArticles, Medline, Web of Science Core Collection, Embase, and PubMed. The search combined keywords such as "intergenerational trauma," "transgenerational trauma," "historical trauma," "secondary traumatization," and "collective trauma."

Studies were included if they investigated the impact of collective intergenerational trauma on second-generation descendants of survivors, used quantitative methods, and were published in English in peer-reviewed journals. Studies were excluded if they were solely conceptual reviews without data collection, used qualitative methods, employed a single-case clinical study design, focused on the impact of intergenerational trauma on third-generation descendants, or studied personal trauma (not collective), such as maternal maltreatment during childhood. No studies were excluded based on the type of collective intergenerational trauma (e.g., Holocaust, civil war, genocide) or geographical location. Initially, 3904 studies were retrieved, which reduced to 1721 after removing duplicates. Two researchers independently reviewed titles and abstracts, resulting in 93 articles. After full-text review, the final selection included 18 studies. The accuracy of data extraction was reviewed by two independent authors, and discrepancies were resolved through discussion until a consensus was reached.

Results

The final selection of studies focused on the intergenerational impact of trauma on second-generation descendants. Studies that were reviews, qualitative, not specific to collective trauma, or focused on third-generation descendants were not included. The quality of the reviewed studies was assessed using a recognized tool, which evaluated 11 specific domains. Most studies met criteria for stating a focused issue, using appropriate methods, employing data collection strategies, presenting results, conducting rigorous data analysis, and clearly stating findings. However, shortcomings were noted in recruitment strategies, the use of accurate and validated measures, sample size, generalizability to local populations, and the value of the research for conclusive evidence. Despite these limitations, the 18 studies were included because they were considered appropriate and relevant to the research objective, data collection, and implications.

The characteristics of the selected studies showed that all 18 used quantitative methods. Eight studies employed a parent-child dyadic design, collecting data from one or both parents and their descendants to assess the trauma experienced by survivor parents and its direct impacts on their descendants’ physiological and psychological outcomes. Ten studies used comparative analyses, comparing two or more groups of descendants—such as offspring of trauma survivors versus those who are not—to examine differences in physiological and psychological outcomes. Three main themes emerged from the analysis: the impacts of intergenerational trauma on (a) epigenetics and physiological outcomes; (b) interpersonal relationships and social identity; and (c) psychological distress and psychopathology.

Three studies investigated the epigenetic and physiological impacts of intergenerational trauma on descendants, consistently showing these effects. For example, two studies found that offspring of Holocaust survivors with parental PTSD exhibited reduced glucocorticoid receptor gene methylation and lower cortisol levels, respectively. Another study revealed that children of mothers exposed to an earthquake had smaller bilateral amygdala volumes. These findings suggest that parental trauma can lead to biological changes in descendants, affecting their stress response systems and brain structures.

Three studies explored the impacts of intergenerational trauma on descendants' interpersonal relationships and social identity, consistently demonstrating effects in both areas. One study found that offspring of Holocaust survivors displayed higher anxiety, avoidance, and defensiveness in interpersonal contexts compared to control groups. Another observed more Holocaust-related imagery in these descendants but no difference in general Jewish identity, along with higher loyalty. A third study found that mothers' PTSD symptoms negatively influenced their children's attitudes toward reconciliation, suggesting that parental mental health can shape second-generation attitudes in post-conflict societies, possibly through witnessing parental distress.

Thirteen studies examined the impact of intergenerational trauma on descendants' psychological distress and psychopathology. These studies covered various trauma types, including war-related trauma in veterans' families and refugees, genocide, the Holocaust, Apartheid, and residential schools. Some studies on war veterans' families consistently showed psychological effects, linking veterans' trauma exposure to their children's phobic anxiety, somatization, and overall psychological distress. Other research on Vietnam War veterans' children found higher rates of trauma exposure, PTSD, and mental health issues, with gender differences observed (daughters with more trauma/PTSD, sons with higher substance use). However, one smaller study on veterans' children did not find significant differences in self-esteem or psychological distress. Studies on war refugees also indicated that parental psychological distress was associated with second-generation distress, and the perceived burden from parental trauma, rather than a PTSD diagnosis alone, was linked to poorer mental health and quality of life in descendants. For collective traumas like Apartheid, Indian Residential Schools, and the Holocaust, findings converged, showing increased psychiatric morbidity, depressive symptoms, and higher levels of depression and anxiety in second-generation descendants. Studies on the Cambodian genocide found adolescents' anxiety and depression were linked to their perceptions of parental trauma, and parental PTSD was associated with greater secondary traumatization and reduced resilience in offspring. However, some research on the Cambodian and Rwandan genocides found no direct link between maternal PTSD symptoms and similar symptoms in their children, though maternal experiences of violence were associated with children's psychological problems indirectly, and maternal PTSD influenced offspring's reconciliation attitudes. These varied results highlight the complexity of trauma transmission, suggesting that different psychological outcomes or societal responses to trauma may influence the manifestation of intergenerational effects.

Discussion

This review aimed to investigate the impacts of intergenerational trauma on second-generation descendants. The evidence from 18 quantitative studies strongly supports the notion that intergenerational trauma significantly affects second-generation descendants across multiple domains. Physiologically, trauma-related changes in stress regulation systems and brain structures were observed, indicating that trauma can be biologically embedded across generations. Socially and relationally, intergenerational trauma shaped interpersonal dynamics and influenced social identity formation, often fostering mistrust, emotional restraint, and heightened moral rigidity. Psychologically, descendants frequently exhibited elevated levels of distress, anxiety, depression, and trauma-related symptoms, with parental PTSD emerging as a notable predictor.

Emerging evidence highlights the physiological and epigenetic consequences of intergenerational trauma. Studies consistently show that parental trauma exposure can alter stress-related biological systems in offspring. For example, offspring of Holocaust survivors with parental PTSD exhibited reduced glucocorticoid receptor gene methylation and lower cortisol levels, markers indicating impaired glucocorticoid regulation and increased stress sensitivity. Reduced methylation of this gene leads to more glucocorticoid receptors, making the body more sensitive to cortisol and enhancing the negative feedback loop in the stress response system, which then reduces cortisol production after stress. Cortisol is vital for regulating the stress response and modulating memory, particularly for traumatic events; lower levels are linked to greater vulnerability to PTSD. An insufficient cortisol response during or after trauma may fail to contain the stress reaction, leading to stronger traumatic memories and heightened fear. Additionally, low cortisol can impair the body's ability to effectively end the stress response, contributing to chronic hyperarousal and anxiety common in PTSD. Similarly, children of earthquake-exposed mothers were found to have significantly smaller amygdala volumes, with the timing of maternal trauma influencing these neural outcomes. The amygdala is central to processing emotions like fear and threat detection. Reduced amygdala volume has been associated with impaired emotional regulation and an overactive stress response, characterized by increased reactivity to perceived threats even in non-threatening environments, which may heighten vulnerability to psychological disorders like PTSD.

Intergenerational trauma also appears to shape both interpersonal relationships and social identity in descendants. Research shows that offspring of trauma survivors can exhibit heightened anxiety, avoidance, and interpersonal defensiveness, along with perceiving their families as less emotionally expressive and more morally rigid. Other findings indicate that descendants may show increased trauma-related imagery and a stronger sense of loyalty, even without significant changes in broader identity markers. In post-genocide societies, parental PTSD symptoms have been linked to more negative attitudes toward reconciliation among descendants, likely influenced by witnessing parental psychological distress rather than directly adopting parental views. These findings suggest that parental trauma can subtly influence how descendants relate to others and construct their social identities, aligning with existing research on how intergenerational trauma can impact feelings of mistrust and fear.

The impact of intergenerational trauma on descendants' psychological distress and psychopathology has been widely explored across various trauma types, including war-related trauma, genocide, and experiences from the Holocaust, Apartheid, and residential schools. These studies collectively highlight significant psychological consequences for descendants, although findings vary based on the specific type of trauma and the outcomes measured. For instance, children of war veterans with PTSD often show increased psychological distress, including anxiety and somatization. Similarly, children of refugees with parental trauma exhibit poorer mental health, sometimes more strongly linked to the perceived emotional burden of parental trauma than a formal PTSD diagnosis. For historical traumas like the Holocaust, Apartheid, and residential schools, descendants often report higher rates of depression, anxiety, and psychiatric issues. Studies on the Cambodian genocide found parental trauma linked to heightened anxiety, depression, and reduced resilience in children. However, research on the Rwandan genocide and some studies on the Cambodian genocide found no direct link between maternal PTSD and similar symptoms in offspring. These discrepancies suggest that trauma may influence broader emotional well-being and coping capacity without always manifesting in specific trauma-related disorders. Societal responses post-genocide, such as timely initiatives for recognition, justice, and reconciliation, may also play a crucial role in reducing trauma transmission across generations.

This study's strength lies in its systematic analysis of all empirical quantitative studies on intergenerational trauma published over the past 25 years, evaluating factors often partially addressed in prior reviews. However, the findings reveal significant heterogeneity in sample types and measurement instruments across studies, hindering direct comparisons and unified conclusions. The small number of researchers investigating intergenerational trauma and the limited generalizability of many study findings necessitate cautious interpretation. The specific nature of collective trauma may also differentially influence intergenerational effects, highlighting the need to examine distinct trauma types separately rather than assuming uniform transmission mechanisms. Most studies relied on cross-sectional designs, limiting the ability to infer causal relationships. Longitudinal studies are crucial for identifying causal pathways and understanding trauma's evolution across generations. Small sample sizes in several studies also undermine statistical power and generalizability. Furthermore, studies often failed to account for parental exposure to other forms of trauma and confounding variables, potentially skewing observed associations. Exclusive recruitment from non-clinical settings might underestimate the clinical significance of intergenerational trauma, and reliance on self-report measures, some of which were not standardized, raises concerns about the validity of reported psychopathology.

To effectively address intergenerational trauma, a multifaceted approach involving therapeutic interventions and community initiatives is required. The physiological and epigenetic evidence, such as reduced cortisol levels, altered gene methylation, and smaller amygdala volumes, suggests that descendants of trauma survivors may have heightened biological sensitivity to stress and impaired emotional regulation. These findings underscore the need for trauma interventions that are not only psychologically informed but also biologically attuned. Recent studies on trauma-focused psychotherapy, including Trauma-Focused Cognitive Behavior Therapy and Eye Movement Desensitization and Reprocessing (EMDR), show promise in reversing some biological effects, such as normalizing stress hormone levels and modulating epigenetic markers. Therefore, mental health professionals should integrate interventions that address the epigenetic and physiological imprints of intergenerational trauma and support stress response regulation. Early screening for heightened biological stress sensitivity, even in individuals without direct trauma exposure, can inform personalized treatment plans, particularly for populations with intergenerational trauma histories where inherited physiological vulnerabilities may not be immediately apparent but significantly influence mental health outcomes. Mental health practitioners must also develop a comprehensive understanding of the cultural and historical contexts shaping intergenerational trauma transmission and its effects. A trauma-informed care framework is essential, recognizing trauma's profound impact on well-being. Professionals are encouraged to proactively assess intergenerational trauma exposure during trauma narrative evaluations, ensuring therapeutic interventions are tailored to how intergenerational trauma influences an individual's psychological well-being, social identity, and potential psychopathological development. Family therapists should also examine intergenerational patterns of behavior and communication that may perpetuate the trauma cycle. At the community level, psychoeducation and awareness campaigns can significantly improve understanding of intergenerational trauma, empowering communities to adopt effective mitigation strategies. Finally, advocating for policies that address root causes of trauma, such as poverty, inequality, and systemic violence, is crucial for a comprehensive effort.

Introduction

A traumatic event is defined as an experience involving actual or threatened death, severe injury, or sexual violence. Exposure to such events can occur in various ways, including direct involvement, witnessing the event, learning it happened to a close relative or friend, or repeatedly encountering distressing details about the event. Throughout history, war and violence have been constant features of human existence.

Currently, over 65 million people worldwide have been displaced by armed conflicts, with more than 21 million classified as refugees, over half of whom are under 18. The impact of war and violence extends beyond societal disruption, deeply affecting individuals' lives. Veterans often suffer long-term psychological and physical health challenges after combat, with Post Traumatic Stress Disorder (PTSD) being a common condition. The effects of war can also extend to veterans' families. Additionally, natural disasters are a significant source of psychological trauma, with research showing that up to 9% of affected individuals develop PTSD.

Other historical traumas, such as the forced displacement of Indigenous children in Canada’s Indian Residential Schools, the 1994 genocide against the Tutsi in Rwanda, and the institutionalized racial oppression under Apartheid in South Africa, have had severe and lasting psychological impacts on those who directly experienced them. The psychological and social consequences of such traumas often extend beyond the individuals who experienced them firsthand, impacting subsequent generations.

Research shows that the harmful effects of trauma can be passed down from one generation of survivors to their children and grandchildren through a phenomenon called intergenerational trauma. This is defined as a situation where descendants of survivors show similar negative emotional and behavioral responses as the survivors themselves.

These responses can include feelings of low self-worth, depression, suicidal thoughts, substance use, dissociation, hypervigilance, intrusive thoughts, difficulty forming relationships and controlling aggression, and extreme reactivity to stress. The impacts of intergenerational trauma are not only emotional and behavioral but can also lead to physiological changes, such as lower cortisol levels, which are linked to a higher risk of developing PTSD. Understanding these impacts on second-generation descendants is crucial for developing effective clinical interventions and supportive policies for survivors' descendants.

Methodology

This systematic review focused on collective trauma, distinguishing it from individual trauma. Collective trauma refers to the psychological impact experienced by a group of people due to events like natural disasters, genocide, war, or pandemics. This type of trauma is tied to shared experiences and emotional reactions within a group and is linked to the social and cultural environment. In contrast, individual trauma comes from events that directly affect one person, such as accidents or assaults, and its effects relate to that person's specific circumstances and history.

The review focused on collective trauma because it affects entire communities, not just individuals. When a group experiences traumatic events, such as war or displacement, the impact can be felt across generations. Collective trauma shapes how people view themselves, interact with others, and how society functions. Unlike individual trauma, collective trauma has a broader social scope and can influence cultural values and the interconnectedness of identities within the group. Understanding collective trauma is essential for developing healing strategies that go beyond individual therapy to include education, public policy, and community support.

This systematic review focused on the impacts of survivors’ trauma on second-generation descendants, distinguishing them from third-generation descendants. This distinction is important because the effects of trauma differ notably between these generations. One meta-analysis found no evidence of trauma-related issues in the third generation of Holocaust survivors, indicating that this generation did not show worse outcomes in areas like general adjustment, aggression, or attachment compared to typical norms or control groups. Other community research also showed that the effects of intergenerational trauma lessened across generations, with reduced consequences on the third generation.

Many quantitative studies explore the impacts of intergenerational collective trauma on second-generation descendants in various contexts, including those descended from survivors of the Holocaust, genocide, war, displacement, and natural disasters. However, these studies present conflicting findings on whether intergenerational collective trauma directly affects the psychological well-being of second-generation descendants. Some studies report an impact, while others do not. For instance, some research found that adult children of Holocaust survivors had higher anxiety, lower self-esteem, and less controlled aggression compared to children of non-survivors. Another study found that offspring of mothers who experienced significant trauma during South African Apartheid showed more psychiatric problems in late adolescence.

On the other hand, some studies have found that the effects of intergenerational trauma do not transfer from one generation to the next. For example, one study found no significant difference in mental health or quality of life between adult children of parents with chronic PTSD and those whose parents did not have PTSD. Another study found no significant link between mothers’ trauma exposure or PTSD symptoms and their adult children’s depression or PTSD symptoms. Therefore, a systematic analysis of these quantitative studies is needed, carefully considering their methodological limitations, such as sample size, study design, and control of other influencing factors.

While a substantial body of literature has examined the impacts of intergenerational collective trauma on second-generation descendants, the existing evidence is spread across different fields and varies greatly in research designs and methods. There is also a lack of systematic reviews that combine these findings. To date, only a few systematic reviews and meta-analyses have focused specifically on intergenerational collective trauma from war and the Holocaust. No systematic reviews have covered all types of collective trauma or provided a comprehensive overview of associated outcomes. This systematic review is therefore essential to fill these gaps by offering a broad summary of the diverse and fragmented research on intergenerational collective trauma, including a wider range of trauma types and outcomes for descendants.

In conclusion, this review examines the impacts of various forms of intergenerational collective trauma, including genocide, the Holocaust, war, historical trauma, and natural disasters. It aims to answer the question: What are the effects of intergenerational collective trauma on the physiological and psychological outcomes of second-generation descendants? The review also discusses study limitations and offers recommendations for future research to improve our understanding of intergenerational trauma and its effects on later generations.

Methodology

A systematic literature search was conducted between June and December 2023, following specific guidelines, to identify studies on intergenerational trauma in second-generation descendants published from 1997 to 2022. This timeframe was chosen to balance historical depth with current findings. Articles were identified through several major academic databases using keywords such as "intergenerational trauma," "transgenerational trauma," "historical trauma," "secondary traumatization," and "collective trauma."

Studies were included if they investigated the impact of collective intergenerational trauma across second-generation descendants, used quantitative methods, and were published in English in peer-reviewed journals. Studies were excluded if they were solely literature reviews without data collection, used qualitative methods, were single case clinical studies, focused on third-generation descendants, or studied personal trauma not considered collective. The initial search yielded 3904 studies. After removing duplicates, 1721 studies remained. Following abstract screening, 93 articles were left, and the final selection included 18 studies after a full-text review. Two independent authors reviewed the accuracy of data extraction and resolved any discrepancies through discussion.

Results

The final selection included studies that focused on the intergenerational impact of trauma on second-generation descendants. Studies that were reviews, qualitative, not specific to collective trauma, or focused on third-generation effects were not included. The quality of the reviewed studies was assessed using a standard tool, evaluating 11 areas such as clear focus, appropriate methods, recruitment, valid measures, data collection, sample size, presentation of results, data analysis, clear findings, applicability, and research value. Most studies met criteria for clear aims, rigorous analysis, and reliable data collection. However, shortcomings were observed in recruitment methods, measurement validity, sample size, generalizability, and practical applicability. Despite these limitations, the 18 studies were included as they were considered appropriate and relevant to the research objectives, data collection, and implications.

Overview of Study Characteristics and Emergent Themes

The selected studies all used quantitative methods. Eight studies used a parent-child dyadic design, collecting data from one or both parents and their descendants to assess the trauma experienced by parents and its direct impacts on their descendants' physiological and psychological outcomes. Ten studies used comparative analyses, comparing two or more groups of descendants (e.g., offspring of trauma survivors versus non-survivors) to examine differences in physiological and psychological outcomes. The analysis revealed themes highlighting the impacts of intergenerational trauma on: (a) epigenetics and physiological outcomes; (b) interpersonal relationships and social identity; and (c) psychological distress and mental health issues.

Physiological Changes in Descendants

Three studies explored the genetic and physiological impacts of intergenerational trauma on descendants. These studies consistently showed effects on both genetic markers and physical outcomes. For example, two studies found that offspring of Holocaust survivors whose parents had PTSD showed reduced gene methylation (a change in gene expression) and lower cortisol levels, respectively. Cortisol helps regulate the stress response, and low levels are linked to a higher predisposition to PTSD. Another study showed that children of mothers exposed to an earthquake had smaller bilateral amygdala volumes, a brain region central to processing fear and threat.

Impacts on Interpersonal Relationships and Social Identity

Three studies explored how intergenerational trauma affects descendants’ interpersonal relationships and social identity. These studies consistently showed effects in both areas. One study found that children of Holocaust survivors displayed higher anxiety, avoidance, and defensiveness compared to control groups. Another observed more Holocaust-related imagery (thoughts, dreams, memories) in descendants but no difference in Jewish identity. A third study found that mothers’ PTSD symptoms negatively influenced their children’s attitudes toward reconciliation, suggesting that observing parental distress played a role. These findings indicate that parental trauma can subtly influence how descendants relate to others and form their social identities.

Psychological Distress and Mental Health Issues

Thirteen studies examined the impact of intergenerational trauma on descendants’ psychological distress and mental health. These were grouped by trauma type: three focused on war-related trauma in veterans’ families, two on war-related trauma in refugees, five on genocide, and three on the Holocaust, apartheid, and residential schools.

War Veterans' Families

Research explored intergenerational trauma in the families of war veterans. Some studies found that trauma exposure in veterans was linked to their children experiencing issues like phobic anxiety, physical symptoms, and overall psychological distress. A large study of Vietnam War veterans' children found higher rates of trauma exposure, PTSD, and other mental health problems compared to control groups. Daughters often experienced more trauma and PTSD, while sons showed higher substance use. In contrast, a smaller study of veterans' children found no significant differences in self-esteem or psychological distress, despite reports of increased family conflict. The authors noted that the small sample size limited the conclusions that could be drawn from these findings.

War Refugees

Studies on refugee families also showed that intergenerational trauma affects the mental health of descendants. For example, one study of Vietnamese refugees found that fathers' psychological distress was linked to their adult children's distress many years later. However, the children were often more resilient than their peers. Another study of World War II refugees found that the perceived burden from parental trauma, rather than a parent's PTSD diagnosis, was more closely tied to poorer mental health and quality of life in the next generation. This suggests that how trauma is understood and felt by descendants can be very important.

Apartheid, Residential School, and Holocaust Trauma

Studies on the intergenerational effects of South African Apartheid, Indian Residential Schools (IRS), and the Holocaust found similar psychological outcomes in second-generation descendants. For instance, adolescents whose mothers experienced more trauma during Apartheid showed increased psychiatric problems later in life. Descendants of IRS survivors reported more depressive symptoms, more negative childhood experiences, and higher rates of adult trauma and discrimination. Children of Holocaust survivors also experienced higher levels of depression and anxiety.

Genocide

Studies on the Cambodian genocide showed mixed results. Some found that adolescents' anxiety and depression were linked to their parents' reported trauma and symptoms. Parental PTSD was also connected to more secondary trauma and less resilience in descendants. However, another study found no direct link between mothers' PTSD symptoms and their children's trauma symptoms, suggesting that trauma might affect general well-being differently than specific trauma disorders. Similarly, studies on the 1994 Rwandan genocide found no direct connection between mothers' trauma or PTSD and their children's psychological issues, especially once the children's own trauma was considered. However, mothers' history of violence in childhood was associated with domestic violence and their children's psychological difficulties.

Discussion

This review aimed to understand how intergenerational trauma affects second-generation descendants. Eighteen quantitative studies were analyzed, all published between 1997 and 2022. The quality of these studies varied, with some limitations in recruitment, measurement, sample size, and generalizability. However, all studies were considered relevant to the research. The findings consistently highlighted three main areas of impact: physiological changes, effects on relationships and social identity, and psychological distress and mental health issues.

Physiological Changes in Descendants

Evidence suggests that intergenerational trauma can cause physiological and genetic changes. Studies showed that children of Holocaust survivors with parents who had PTSD had altered gene methylation (a change in gene expression) and lower cortisol levels, indicating problems with stress regulation. Lower cortisol is linked to a higher risk of PTSD. Similarly, children of mothers exposed to earthquakes had smaller amygdala volumes, a brain region important for processing fear and threat. A reduced amygdala volume can lead to poor emotional regulation and an overactive stress response. These findings point to a biological impact of trauma across generations.

Impacts on Interpersonal Relationships and Social Identity

Intergenerational trauma appears to shape both personal relationships and social identity in descendants. Studies found that children of trauma survivors showed more anxiety, avoidance, and defensiveness in relationships. They also perceived their families as less expressive and more rigid about morals. Descendants reported more trauma-related thoughts and stronger loyalty, even if their broader identity markers didn't change significantly. In societies affected by genocide, parental PTSD was linked to more negative attitudes toward reconciliation in descendants, possibly because they witnessed their parents' distress. These findings suggest that parental trauma can subtly influence how descendants interact with others and form their sense of self.

Psychological Distress and Mental Health Issues

The psychological effects of intergenerational trauma on descendants have been widely studied across various types of trauma, including war-related events, genocide, the Holocaust, apartheid, and residential schools. These studies consistently show significant psychological consequences for descendants, though the specific findings can differ depending on the type of trauma.

For families of war veterans, research indicates that the trauma experienced by veterans, especially those with PTSD, profoundly affects their children. Studies found that children of veterans with PTSD experienced increased psychological distress, including anxiety and physical symptoms. A large study of Vietnam War veterans' children showed higher rates of PTSD and trauma exposure. However, one smaller study found no significant psychological distress in children, which was attributed to the small sample size. These studies generally suggest that war's psychological impact extends to the next generation.

Studies on war refugees further highlight the lasting effects of intergenerational trauma. Trauma experienced by refugee parents, particularly those with PTSD, had a deep impact on their children's mental health. One study found that fathers' psychological distress was especially influential. Another noted that the emotional burden children felt from parental trauma was a stronger predictor of poor mental health than a parent's PTSD diagnosis alone. This suggests that how descendants perceive and process the trauma is key.

Research on the Holocaust, apartheid, and residential schools also revealed significant psychological issues in descendants. Adolescents whose mothers endured high levels of trauma during apartheid later showed increased psychiatric problems. Descendants of Indian Residential School survivors reported more depressive symptoms and higher rates of adverse childhood experiences. Children of Holocaust survivors also had higher levels of depression and anxiety, with maternal PTSD being a strong factor in transmitting these symptoms.

Studies on the Cambodian and Rwandan genocides present a more complex picture. For the Cambodian genocide, some research showed that parental trauma was linked to increased anxiety, depression, and reduced resilience in children. However, another study found no direct link between mothers' PTSD symptoms and their children's trauma symptoms, suggesting that trauma might affect general emotional well-being differently than specific trauma disorders. Similarly, studies on the Rwandan genocide found no direct connection between maternal trauma or PTSD and their children's psychological symptoms, once the child's own trauma was accounted for. These studies suggest that societal responses to genocide, such as reconciliation efforts, might influence how trauma is passed down.

Methodological Issues

This study's strength lies in its systematic analysis of all quantitative studies on intergenerational trauma published over the past 25 years. However, despite this focus, findings showed significant variety in sample types and measurement instruments, making direct comparisons difficult. Only a small number of researchers have investigated intergenerational trauma, and many studies had findings that were not widely generalizable, requiring careful interpretation. Furthermore, the nature of collective trauma itself may influence its intergenerational effects differently, emphasizing the need to examine specific trauma types separately, rather than assuming a uniform mechanism of transmission.

Studies predominantly relied on cross-sectional designs, which prevent drawing conclusions about cause and effect regarding intergenerational trauma. Longitudinal studies are crucial for identifying causal pathways and understanding how intergenerational trauma evolves. Small sample sizes in several studies also reduced their statistical power and ability to generalize findings beyond the studied populations. Additionally, the studies often failed to account for parental exposure to other forms of trauma and other influencing factors, potentially skewing the observed associations. The exclusive recruitment from non-clinical settings may also lead to an underestimation of the clinical significance of intergenerational trauma. Lastly, relying on self-report measures, where some were not standardized, raises concerns about the validity of reported psychological issues.

Recommendations for Clinical Practice

This review strongly supports the notion that intergenerational trauma can profoundly affect second-generation descendants across multiple areas. Physiologically, trauma-related changes in stress regulation systems and brain structures were observed, suggesting that trauma can be biologically passed down across generations. Socially and relationally, intergenerational trauma shaped interpersonal dynamics and influenced social identity formation, often fostering mistrust, emotional restraint, and heightened moral rigidity. Psychologically, descendants exhibited heightened levels of distress, anxiety, depression, and trauma-related symptoms, with parental PTSD emerging as a significant predictor.

To effectively address intergenerational trauma, a comprehensive approach incorporating both therapeutic interventions and community initiatives is required. The emerging physiological evidence, such as reduced cortisol levels, altered gene methylation, and smaller amygdala volumes, suggests that descendants of trauma survivors may have a heightened biological sensitivity to stress and impaired emotional regulation. These findings emphasize the need for trauma interventions that are not only psychologically informed but also biologically attuned. Recent studies on trauma-focused psychotherapy, including Trauma-Focused Cognitive Behavioral Therapy and EMDR (Eye Movement Desensitization and Reprocessing), have begun to show promise in reversing some of these biological effects, such as normalizing stress hormone levels and modulating genetic markers. Therefore, mental health professionals should integrate such interventions that address the genetic and physiological imprints of intergenerational trauma and support the regulation of the stress response.

Additionally, early screening for heightened biological stress sensitivity, even in individuals without direct trauma exposure, can inform personalized treatment planning. This is especially relevant for populations with intergenerational trauma histories, where inherited physiological vulnerabilities may not be immediately visible but still significantly influence mental health outcomes. Mental health practitioners must also develop a comprehensive understanding of the cultural and historical contexts that shape the transmission of intergenerational trauma and its effects on second-generation descendants. A trauma-informed care framework is crucial, recognizing the profound impact trauma has on a descendant’s well-being. Mental health professionals are encouraged to proactively assess exposure to intergenerational trauma during the trauma narrative evaluation, ensuring that therapeutic interventions are tailored to how intergenerational trauma influences an individual’s psychological well-being, social identity, and potential development of mental health conditions. Moreover, this approach requires family therapists to examine intergenerational patterns of behavior and communication that may perpetuate the cycle of trauma. At the community level, psychoeducation and awareness campaigns can significantly improve understanding of intergenerational trauma, empowering communities to adopt effective strategies to lessen its impact. Finally, advocating for policies that address the root causes of trauma, such as poverty, inequality, and systemic violence, is essential for this comprehensive effort.

Introduction

A traumatic event is defined as an experience involving actual or threatened death, serious injury, or sexual violence. People can be exposed to such events directly, by witnessing them, by learning they happened to a close family member or friend, or by repeatedly dealing with upsetting details related to the event. Throughout history, war and violence have consistently been a part of human life. Currently, more than 65 million people globally have been forced from their homes due to conflicts, with over 21 million recognized as refugees. The effects of war and violence go beyond causing societal problems; they deeply impact individual lives.

Many veterans often face lasting mental and physical health issues after combat, with Post-Traumatic Stress Disorder (PTSD) being common. The effects of war can also extend to their families. Besides war, natural disasters are another major source of psychological trauma; studies show that up to 9% of people affected by natural disasters develop PTSD. Other historical traumas, like the forced removal of Indigenous children in Canada's Indian Residential Schools, the 1994 genocide in Rwanda, and the racial oppression in South Africa under Apartheid, have also caused severe and long-term psychological harm to those who directly experienced them.

Research shows that the harmful effects of trauma can be passed down from one generation of survivors to their children and grandchildren, a process known as intergenerational trauma. This means that descendants of trauma survivors can show similar emotional and behavioral problems as the original survivors. These problems can include low self-worth, depression, suicidal thoughts, substance use, feeling detached, being overly alert, intrusive thoughts, and trouble forming relationships or managing anger.

The impact of intergenerational trauma is not only emotional and behavioral but also involves physical changes. For example, some studies found that mothers' PTSD and their age when they experienced the Holocaust predicted lower cortisol levels in their children. Cortisol helps regulate the body's stress response, and low levels are linked to a higher risk of PTSD. This suggests that understanding intergenerational trauma's impact on the second generation is crucial for developing effective treatments and supportive policies.

This review focuses on collective trauma, which is different from individual trauma. Collective trauma is the psychological impact a group of people experiences from shared traumatic events like natural disasters, genocide, war, or pandemics. It affects not just individuals but entire communities, shaping how people see themselves, interact with others, and how society functions. In contrast, individual trauma affects one person from events like accidents or assaults. This review focuses on collective trauma because its effects are broader, influencing cultural values and the connections between people within a group. Understanding it is key for creating healing strategies that go beyond individual therapy to include education, public policy, and community support.

This review specifically looks at the impacts of survivors' trauma on second-generation descendants, distinguishing them from third-generation descendants because the effects often lessen over time. Studies have generally found little to no evidence of lasting trauma effects in the third generation of survivors, showing improved well-being compared to earlier generations. This study aims to bring together existing research to answer the question: What are the effects of intergenerational collective trauma on the physical and mental health outcomes of second-generation descendants? It also discusses study limitations and suggests future research.

Methodology

A thorough literature search was conducted from June to December 2023, following standard guidelines for systematic reviews. The goal was to find studies on intergenerational trauma in second-generation descendants published over 25 years (1997–2022). This timeframe balances looking at historical data with including modern findings on intergenerational trauma.

Studies were identified using various medical and psychological databases and keywords like "intergenerational trauma," "transgenerational trauma," "historical trauma," "secondary traumatization," and "collective trauma." To be included, studies had to investigate the impact of collective intergenerational trauma on second-generation descendants, use quantitative methods, and be published in English in peer-reviewed journals.

Studies were excluded if they were only reviews, used qualitative methods, focused on single clinical cases, examined third-generation descendants, or dealt with personal trauma not related to a collective event (like childhood maltreatment). The type of collective intergenerational trauma (e.g., Holocaust, civil war, genocide) or geographical location did not lead to exclusion. Initially, 3904 studies were found. After removing duplicates and screening titles and abstracts, 93 articles remained. From these, 18 studies were chosen for the final review after a full-text assessment. Two researchers independently reviewed and extracted data, resolving any disagreements to ensure accuracy.

Results

The final selection of 18 studies focused on the intergenerational impact of collective trauma on second-generation descendants using quantitative methods. Studies that were reviews, qualitative, not specific to collective trauma, or focused on third-generation effects were not included. A quality assessment tool (CASP) was used to evaluate these studies. Most studies had clear goals, appropriate methods, rigorous analysis, and clearly stated findings. However, some limitations were noted, such as less-than-ideal recruitment methods, non-standardized measures, small sample sizes, limited ability to apply findings to a wider population, and providing only preliminary insights. Despite these issues, all 18 studies were considered relevant to the review's objectives.

The included studies used two main approaches: either a parent-child study design, collecting data from parents and their children on trauma experienced by the parents and its effects on their descendants, or comparative analyses, comparing groups of descendants from trauma survivors with groups of those not from survivors. The analysis revealed three main areas where intergenerational trauma impacts descendants: (a) biological and genetic changes; (b) relationships with others and personal identity; and (c) psychological distress and mental health conditions.

Impacts of intergenerational trauma on the epigenetics and physiology of descendants

Three studies consistently showed that intergenerational trauma affects the biology and genetics of descendants. For instance, children of Holocaust survivors with parents who had PTSD showed changes in a specific gene and lower levels of cortisol, a hormone involved in stress response. Other research found that children of mothers exposed to an earthquake had smaller brain regions (amygdala volumes) related to processing emotions like fear. These findings suggest that the trauma experienced by parents can lead to biological changes in their children, potentially making them more vulnerable to stress.

Impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity

Three studies also showed that intergenerational trauma impacts how descendants relate to others and their sense of self. Children of Holocaust survivors, for example, often showed higher anxiety, avoidance in relationships, and a tendency to be defensive. They also perceived their families as less emotionally expressive and more focused on responsibility and moral values. Another study found that descendants had more thoughts and dreams related to the Holocaust and a stronger sense of loyalty, even if their overall religious identity wasn't different. In communities affected by genocide, mothers' PTSD symptoms were linked to their children having negative attitudes toward reconciliation, suggesting that witnessing parental distress influences children's social views.

Impacts of intergenerational trauma on descendants’ psychological distress and psychopathology

Thirteen studies explored how intergenerational trauma affects descendants' mental health, categorized by trauma type: war veterans' families, war refugees, and specific historical traumas like the Holocaust, Apartheid, and residential schools, and genocide. Overall, these studies show that the trauma experienced by parents can have significant psychological consequences for their children, though findings can vary depending on the specific trauma and the research methods used.

For war veterans' families, some studies found that children of veterans with PTSD experienced more psychological distress, including anxiety and physical symptoms. Children of Vietnam War veterans also showed higher rates of trauma exposure and PTSD. However, one study with a smaller sample size did not find significant differences in psychological distress, suggesting that sample size can influence results. Similarly, studies on war refugees indicated that parental trauma significantly impacts children's mental health, with paternal psychological distress sometimes being a strong predictor. Some research also suggested that children's perception of their parents' trauma burden, rather than the parents' PTSD diagnosis alone, was a stronger indicator of the children's mental health.

Studies on specific historical traumas also revealed notable psychological outcomes. Children whose mothers experienced high levels of trauma during South African Apartheid showed increased mental health problems in late adolescence. Descendants of Indian Residential School survivors had more depressive symptoms and higher exposure to adverse childhood experiences. Children of Holocaust survivors also reported higher levels of depression and anxiety, with mothers' PTSD being a particularly strong factor.

Research on the Cambodian and Rwandan genocides presented mixed findings. Some studies on Cambodian genocide survivors' children found links between parental trauma and increased anxiety, depression, and reduced resilience in adolescents. Other research, however, found no direct connection between mothers' PTSD symptoms and similar symptoms in their children, suggesting that trauma might affect general well-being differently than specific trauma-related disorders. In studies on the Rwandan genocide, no significant direct link was found between maternal trauma or PTSD and their children's psychological symptoms once the children's own trauma was considered. However, an indirect link was observed where mothers' experiences of childhood violence (not their PTSD) were associated with domestic violence and children's psychological difficulties. These varying results highlight the importance of considering different psychological outcomes and specific societal responses after such events.

Discussion

This review aimed to explore the effects of intergenerational trauma on second-generation descendants. Based on 18 quantitative studies published over the past 25 years, the evidence strongly suggests that intergenerational trauma can deeply affect children of survivors across several areas. These include biological changes related to stress, impacts on social relationships and identity, and increased psychological distress and mental health problems.

Emerging evidence points to physiological and genetic changes, such as reduced cortisol levels and altered gene methylation, which suggest that descendants may have a heightened biological sensitivity to stress. These changes in the body's stress response system can make individuals more vulnerable to mental health issues like PTSD. Similarly, studies showing smaller brain regions (amygdala volumes) in children of traumatized mothers indicate impaired emotional regulation and a tendency to overreact to perceived threats, even in safe environments.

Intergenerational trauma also appears to influence how descendants form relationships and their social identity. For instance, children of trauma survivors often show higher anxiety, avoidance in relationships, and perceive their families as less openly emotional. They may also have a stronger sense of loyalty to their family's traumatic past. In post-genocide societies, parental PTSD has been linked to negative attitudes toward reconciliation in children, shaped by observing their parents' distress. These findings align with research showing that intergenerational trauma from events like the Holocaust can lead to feelings of mistrust and fear towards others.

The impact of intergenerational trauma on descendants' psychological distress and mental health conditions has been widely studied, with findings varying across different types of trauma. Children of war veterans often show increased psychological distress, including anxiety and PTSD. Similarly, children of refugees can be significantly affected, with parental trauma influencing their mental health. In these cases, the child's perception of the parent's trauma can sometimes be a stronger predictor of their own well-being than the parent's actual PTSD diagnosis.

For historical traumas like the Holocaust, Apartheid, and residential schools, studies consistently reveal significant psychological issues in descendants, such as higher rates of depression, anxiety, and adverse childhood experiences. Maternal PTSD is often a strong factor in passing down these symptoms. However, studies on genocides, particularly the Rwandan genocide, present a more complex picture. Some research shows direct links between parental trauma and psychological issues in children, while others find no direct association between parental PTSD and similar symptoms in their children, suggesting that trauma may affect general emotional well-being differently than specific trauma disorders. It's possible that a society's response after genocide, focusing on recognition and reconciliation, can reduce the transmission of trauma to future generations, as seen in Rwanda.

This review, while comprehensive, has certain limitations. The studies examined used diverse methods, making direct comparisons difficult. Only a limited number of researchers have explored intergenerational trauma, and many studies had findings that may not apply broadly to all populations. The nature of different collective traumas might also influence their effects differently, requiring specific examination for each trauma type. Most studies used cross-sectional designs, which only capture a snapshot in time and cannot prove cause and effect. Many studies also had small sample sizes, reducing the reliability and generalizability of their findings. Furthermore, some studies did not account for other forms of trauma parents might have experienced or other influencing factors. The reliance on self-reported measures, some of which were not standardized, also raises concerns about the accuracy of reported mental health problems.

To effectively address intergenerational trauma, a broad approach combining therapy and community efforts is needed. Given the evidence of biological and genetic changes, such as altered stress hormone levels and brain structures, trauma interventions should be both psychologically informed and biologically aware. Therapies like Trauma-Focused Cognitive Behavior Therapy and Eye Movement Desensitization and Reprocessing (EMDR) have shown promise in reversing some of these biological effects. Therefore, mental health professionals should integrate these interventions to support stress regulation. Early screening for high biological stress sensitivity, even in individuals without direct trauma, can help create personalized treatment plans, especially for populations with a history of intergenerational trauma.

Mental health practitioners also need a deep understanding of the cultural and historical contexts of intergenerational trauma. A trauma-informed approach is vital, recognizing the profound impact trauma has on a person's well-being. Professionals should actively assess for intergenerational trauma during evaluations, tailoring therapies to address how it affects an individual's mental health, social identity, and potential for developing mental health conditions. Family therapists should explore intergenerational patterns of behavior and communication that might continue the cycle of trauma. At the community level, education and awareness campaigns can help people understand intergenerational trauma better and adopt effective strategies to lessen its impact. Finally, supporting policies that tackle the root causes of trauma, such as poverty, inequality, and systemic violence, is crucial for a complete solution.

Introduction

Experts say a traumatic event is when someone faces real or threatened death, serious harm, or sexual violence. This can happen if a person goes through the event themselves, sees it happen to others, learns it happened to a loved one, or often hears upsetting details about it.

War and violence have always been a part of human history. Today, over 65 million people have been forced to leave their homes because of fighting, with many being children. The effects of war and violence deeply change people's lives. Soldiers often face lasting mental and physical problems after fighting, like Post-Traumatic Stress Disorder (PTSD). This harm can reach their families too.

Natural disasters also cause much mental harm, with some people developing PTSD. Other sad historical events like forced displacement, genocide, and racial unfairness have caused deep and lasting mental pain for those who lived through them.

Studies show that the bad effects of trauma can be passed down from people who lived through it to their children and grandchildren. This is called intergenerational trauma. Children of trauma survivors may show similar upset feelings and behaviors, like feeling bad about themselves, sadness, thoughts of suicide, drug use, feeling spaced out, being very watchful, having unwanted thoughts, or having trouble with relationships. Trauma can also change how the body works. For example, some children of mothers who went through the Holocaust had lower levels of cortisol, a hormone that helps handle stress. Low cortisol can make someone more likely to get PTSD. Knowing about these effects is important to help people whose families have gone through trauma.

This review looks at "collective trauma," which is trauma that affects a whole group of people, like from natural disasters, war, or widespread illness. This is different from "individual trauma," which affects only one person, like from an accident. Collective trauma is important because it changes not just single people but entire communities and how they live for generations. Learning about collective trauma helps create ways to heal that involve everyone, not just one person, through teaching, public rules, and community help.

Methodology

This study looked for other studies about how trauma passes down through families. The search happened from June to December 2023, looking for papers published between 1997 and 2022. The goal was to find studies about how "collective trauma" affects the children and grandchildren of survivors. Researchers used many search terms like "intergenerational trauma" in different science databases. Only studies that (a) looked at collective trauma passed down to the second generation, (b) used numbers and facts (not just ideas), and (c) were written in English in science journals were included. Studies that were just reviews, used interviews, looked at single cases, focused on the third generation, or were about personal trauma (not group trauma) were left out. The type of trauma or where it happened did not stop a study from being included.

At first, 3904 studies were found. After removing copies, 1721 studies were left. Two researchers then looked at the titles and short summaries of these studies. This narrowed it down to 93 papers. After reading these full papers, 18 studies were chosen for this review. Two different authors checked the information taken from these 18 studies to make sure it was correct. If they disagreed, they talked about it until they both agreed.

Results

The chosen studies focused on how trauma affects the children and grandchildren of survivors. Studies that were reviews, used interviews, or looked at third-generation effects were not included. A tool called CASP was used to check the quality of the 18 studies. It looked at 11 things, like how clear the problem was, if the methods were good, and if enough people were studied. Most studies did well on some points, but many had issues with how they found people to study, how they measured things, or if they had enough people. Also, many results might not apply to everyone, and some findings were just early ideas, not final answers. Still, all 18 studies were useful and fit the purpose of this review.

Overview of study characteristics and emergent themes

This review looked at 18 studies, all using numbers and facts. Eight studies looked at parents and their children together to see how trauma affected them. Ten studies compared groups of children, like those from trauma survivors versus those who were not, to find differences in their physical and mental health. The main ideas from these studies showed that trauma passed down through families affects: (a) how people's bodies work, (b) how they get along with others and see themselves, and (c) their mental health problems.

Impacts of intergenerational trauma on the epigenetics and physiology of descendants

Three studies looked at how trauma passed down through families affects the body. They found that children of trauma survivors can have changes in their bodies. These studies found that the children of Holocaust survivors with parents who had PTSD showed changes in a specific gene linked to stress. These children also had lower cortisol levels, a hormone that helps control stress. The effects were stronger if both parents had PTSD. Another study found that children of mothers exposed to an earthquake had smaller amygdala, a brain area linked to fear. This suggests that trauma can affect a person's stress system and brain structure even across generations.

Impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity

Three studies looked at how trauma from past generations affects how people get along with others and how they see themselves. These studies showed that intergenerational trauma can make people more anxious, avoid others, and be more defensive.

One study found that children of Holocaust survivors were more likely to avoid disagreements, be careful, and worry about relationships. They also seemed less able to speak up for themselves and saw their families as less open about feelings. Another study found these children had more thoughts and dreams related to the Holocaust, and a stronger sense of loyalty. In a study about the Rwandan genocide, mothers with PTSD influenced their children to have negative feelings about making peace, likely because they saw their mothers' pain. These studies show that past trauma can change how people act with others and how they understand their place in the world.

Impacts of intergenerational trauma on descendants’ psychological distress and psychopathology

Thirteen studies looked at how trauma passed down through families affects people's mental health problems and worries. These studies were grouped by the type of trauma: war veterans' families, war refugees, genocide, and events like the Holocaust, apartheid, and residential schools.

War veterans’ families

Studies looked at how trauma affects the children of war veterans. One study of Portuguese veterans found that children of veterans who experienced trauma had more fear, body pains from stress, and general mental distress. Another study on Vietnam War veterans' children found they had more trauma, PTSD, and mental health problems compared to other children. Daughters had more trauma and PTSD, while sons used more drugs or alcohol. However, a smaller study found no major differences in self-worth or mental worry for veterans' children, perhaps because they studied too few people.

War refugees

Studies on war refugees also point to lasting effects of trauma on future generations. Trauma from refugee parents, especially those with PTSD, strongly affected their children's mental health. Sometimes, a father's trauma was especially important. It was also found that how much the children felt the weight of their parents' trauma was a better sign of poor mental health than just if the parents had PTSD. This means that how children understand and feel about the trauma might be more important.

Apartheid, residential school, and holocaust

Studies on trauma from South African Apartheid, Indian Residential Schools, and the Holocaust all found similar mental health effects on the next generation. For example, children of mothers who went through high levels of trauma during Apartheid had more mental health problems later. Children of Indian Residential School survivors also had more signs of sadness, bad childhood experiences, and experienced more discrimination. Children of Holocaust survivors often had more sadness and worry. When mothers had PTSD, their children were more likely to have PTSD too, and both parents' PTSD was linked to children's sadness.

Genocide

Studies on the Cambodian genocide found different results. Some found that teenagers' worry and sadness were linked to their parents' trauma. They also found that parents' PTSD was linked to more trauma and less strength in their children. However, another study found no direct link between mothers' PTSD and their children's PTSD symptoms. This might mean that parents' trauma can affect children's overall feelings but not always lead to the same specific trauma problems.

Studies on the Rwandan genocide also found no direct link between mothers' trauma or PTSD and their children's mental problems, after considering the children's own experiences. However, children's problems were linked to mothers using violence in the home, which was connected to the mothers' own past experiences of violence. The way a society deals with genocide after it happens, like seeking justice and peace, might help reduce how trauma passes down through families.

Discussion

This review looked at how trauma passed down through families affects the children of survivors. It included 18 studies from 1997 to 2022. While most studies had clear goals and good analysis, some had problems with how they found people, how they measured things, or if they had enough people, meaning their findings might not apply to everyone. Still, all studies were important for the review. They showed three main ways that trauma from past generations affects people: (a) changes in the body, (b) how people relate to others and see themselves, and (c) mental health problems.

Parental trauma and descendants’ physiological changes

New evidence shows that trauma in parents can lead to physical changes in their children. Studies found that children of Holocaust survivors with parents who had PTSD showed changes in how their bodies handle stress. They had lower levels of cortisol, a hormone important for dealing with stress. If the body has too little cortisol, it can make someone more likely to get PTSD and feel very anxious.

Another study found that children of mothers who went through an earthquake had smaller amygdala, which is a part of the brain that handles fear. A smaller amygdala can make it harder for a person to control their feelings and can lead to overreacting to danger, even when there isn't any. This can make someone more likely to have mental health problems like PTSD. These findings show that trauma can be "written" into a person's biology across generations.

Impacts of intergenerational trauma on descendants’ interpersonal relationships and social identity

Trauma passed down through families seems to change how people connect with others and how they see themselves. Children of trauma survivors often show more worry, avoid others, and act defensively. They may also see their families as less open about feelings and very strict about right and wrong. These children sometimes have more thoughts and images related to the past trauma and feel a strong sense of loyalty.

After a genocide, studies found that parents with PTSD symptoms made their children feel less positive about making peace. This likely happened because the children saw their parents' pain, not just by copying their parents' ideas. This shows that parents' trauma can quietly change how children act with others and how they form their sense of self. Past studies on the Holocaust and genocides also show that this kind of trauma can make people feel distrust and fear toward others.

Impacts of intergenerational trauma on descendants’ psychological distress and psychopathology

Many studies have looked at how trauma from past generations affects the mental health of children and grandchildren. They show that there are real mental health problems for these descendants, though the exact findings can change depending on the type of trauma.

Studies on war veterans' families show that trauma from war, especially PTSD, deeply affects their children. Children of veterans with PTSD often showed more mental worry, fears, and body pains due to stress. They also had more PTSD and other trauma. Even though one small study found no major effects, most research agrees that the mental pain of war reaches beyond the soldiers to their children.

Studies on war refugees also point to lasting effects of trauma on future generations. Trauma from refugee parents, especially those with PTSD, strongly affected their children's mental health. Sometimes, a father's trauma was especially important. It was also found that how much the children felt the weight of their parents' trauma was a better sign of poor mental health than just if the parents had PTSD. This means that how children understand and feel about the trauma might be more important.

For the Holocaust, apartheid, and residential schools, studies found clear mental health effects on the children. Children of mothers who suffered greatly during apartheid showed more mental illness. Descendants of Indian Residential School survivors had more sadness and bad childhood events. Children of Holocaust survivors had more sadness and worry, especially if their mothers had PTSD.

Studies on the Cambodian genocide showed that parents' trauma was linked to more worry, sadness, and less strength in their children, though some studies found no direct link to children's PTSD symptoms. Studies on the Rwandan genocide also found no direct link between mothers' trauma and their children's mental problems, after considering the children's own experiences. However, children's problems were linked to mothers using violence at home, which was connected to the mothers' own past experiences of violence. The way a society deals with genocide after it happens, like seeking justice and peace, might help reduce how trauma passes down through families.

Methodological issues

This study was strong because it looked at many research papers on intergenerational trauma from the last 25 years. However, even though it only used studies with numbers and facts, the studies themselves were very different. They used different types of people and different ways to measure things, which made it hard to compare them directly or draw simple conclusions.

Not many researchers have looked at intergenerational trauma, and many studies' findings might not apply to everyone. It's also possible that different types of group trauma affect families in different ways. Most studies only looked at one point in time, which makes it hard to say if trauma caused certain effects. Studies that follow people over many years are needed to understand how trauma changes over time. Some studies had too few people, which means their results might not be very strong or apply to a wider group. Also, these studies didn't always consider other traumas parents might have had, or other things that could have affected the results. Using only people who weren't getting clinical help might also mean the full impact of trauma was not seen. Lastly, many studies relied on people reporting their own feelings, and some of the tools used were not always standard, which could make the results less accurate.

Recommendations for clinical practice

This review wanted to know if trauma passed down through families affects the bodies and minds of children and grandchildren. The 18 studies strongly show that it does. Physically, trauma was linked to changes in how the body handles stress and in brain parts, meaning trauma can be "built into" the body across generations. Socially, it changed how people connect with others and how they see themselves, often leading to distrust, holding back feelings, and being very strict about rules. Mentally, descendants showed more worry, sadness, and signs of trauma, especially if their parents had PTSD.

To help people affected by trauma passed down through families, many types of help are needed, including therapy and community efforts. The physical changes seen in children of trauma survivors, like lower stress hormones or smaller brain parts, mean they might be more sensitive to stress and have trouble controlling their feelings. So, therapies should not just help the mind but also consider these body changes. Some therapies, like Trauma-Focused Cognitive Behavior Therapy, are starting to show they can help reverse some of these body changes. Checking early for high stress sensitivity, even in people who haven't directly experienced trauma, can help plan better care. This is very important for families with a history of trauma, as hidden body weaknesses can still affect mental health.

Mental health helpers need to understand the culture and history behind how trauma is passed down. They should always keep trauma in mind when working with people, knowing how deeply it can affect a person's life. Professionals should ask about family trauma history to make sure treatments fit the person's needs for their mental health, sense of self, and any mental problems. Family therapists should look at how family behaviors might keep trauma going. In communities, teaching people about intergenerational trauma can help everyone learn ways to lessen its effects. Also, pushing for rules and laws that fix the main causes of trauma, like poverty and unfairness, is a key part of this overall effort.