The United Nations High Commissioner for Refugees indicated in its 2020 report that 1% of the world’s population, or 1 in 95 people, are forcibly displaced because of persecution and human rights violations, conflict and violence, and climate disasters. The United Nations defines 3 categories of forcibly displaced persons: internally displaced people, refugees, and asylum-seekers. Internally displaced people have not crossed a border to find safety. Unlike refugees, they are displaced within their home countries. Refugees are people who flee their countries of origin due to conflict or persecution. An asylum-seeker is someone who, similarly to a refugee, has left their country in search of safety but has not yet been legally recognized as a refugee. Forcibly displaced persons differ from migrants, people who are outside of their countries of origin for purposes of work, study, or family, or to leave poverty, political unrest, violence, or natural disasters. As such, while migrants may not fit the definition of forcibly displaced persons, they may still be in danger in their home countries and face a multitude of stressors, and the same may be true for internally displaced people.

Many forcibly displaced persons are exposed to traumatic events—war, loss of loved ones, natural disaster, physical or sexual assault, and fires and explosions. As a result of these severe, chronic, and cumulative traumas, risk for posttraumatic stress disorder (PTSD), anxiety, depression, and other mental and physical health consequences is increased. Deprivation, displacement, and postmigration difficulties —including discrimination and harassment—also significantly contribute to outcomes. Syrian refugees, for example, may be 10 times more likely to develop PTSD and other trauma-related psychopathology than the general population. Across Syrian, Rohingya, Karen, Kosovan, Iraqi, Kurdish, Nepalian, and other refugee cohorts, rates of PTSD, anxiety, and depression range from 13.9% to 83.4%, from 16.7% to 90%, and from 20% to 89%, respectively. Youths who resettle as refugees are similarly affected. While trauma has often been the main focus of research, refugees are exposed to unique chronic stressors before, during, and after displacement. Lack of access to basic health care, food, safety, and financial resources; detachment from the familiar environment and loved ones; chronic uncertainty about their future during transition; acculturative stress; role transition and changes within the family; and marginalization and exposure to prejudice in host countries are just some of the abundant chronic stressors that refugees endure for years and decades.

El-Khoury et al. succinctly define torture as systematic and deliberate infliction of severe pain or suffering on a person over whom the perpetrator holds power or control to generate a desired response from the tortured individual. Regardless of the form of torture, it will affect both physical and mental aspects of health. Some of the long-lasting effects include memory impairment, somatic complaints, feelings of humiliation, PTSD, depression, anxiety, pain, incoherent speech, disorientation, and paranoia; these outcomes are worsened by postmigration difficulties and prolonged wait times to receive clinical services. Up to 88.3%, 91%, and 94% of people who experience torture may experience PTSD, anxiety, and depression, respectively. Torture survivors tend to be less responsive to evidence-based treatments for PTSD compared with other trauma-exposed groups, signaling a need to better understand the unique effects of torture to inform more efficacious interventions.

Regardless of the reason for displacement, these populations have experienced a broad and unique range of trauma and chronic stress at the individual, familial, community, and societal levels. In this article, we review how neuroscience and biological psychiatry can address mental health equity for individuals who have been uprooted in relation to land (Indigenous communities, migrant and refugee families, and individuals seeking asylum) with a focus on refugee communities, where our expertise lies. We 1) review what is known about the biological impacts of trauma and stress related to forced displacement, 2) highlight critical gaps in the literature, 3) note the challenges in this field that may contribute to such critical gaps, 4) discuss why overcoming these challenges and addressing these gaps is necessary, and 5) provide a call to action with recommendations to improve biological psychiatry research in this area.

What We Know

There have been abundant advances in our understanding of the neurobiological effects of trauma and stress on the brain and the body in recent decades. Many neuroimaging, genetic and epigenetic, neuroendocrine, and psychophysiological studies have examined the effects of trauma and cumulative stress. However, most of these studies are in military and Western populations and countries. On the other hand, research on trauma and stress among refugees and migrants has been mostly focused on prevalence of mental illness (specifically PTSD) and the role of environmental stressors on psychopathology. Neuroscience researchers have been less involved in this area, and studies are mostly published in journals with nonbiological foci.

There are a limited number of neuroimaging studies in refugee cohorts. Kim and colleagues stand out, having published findings from traumatized North Korean refugees. Findings from this team indicated that trauma-exposed North Korean refugees had increased amygdala and hippocampal activation in response to negative pictures compared with non–trauma-exposed South Korean volunteers, and that the refugee group showed greater connectivity between the prefrontal cortex, amygdala, and hippocampus during an emotion regulation task. Hippocampal response was positively correlated with PTSD symptoms in the refugee group. While the finding regarding amygdala and hippocampal activation in response to negative pictures aligned with the extant literature (33,34), the findings regarding increased connectivity between limbic and emotion regulation regions did not. The authors attributed this to the possibility of refugees’ use of emotion suppression strategies as a coping mechanism given their lived experiences. This finding supports hypotheses regarding environmental sources of variances in the neurobiological processes that underlie psychiatric phenotypes, with clinical implications. Another study of structural variation in trauma-exposed PTSD+, trauma-exposed PTSD−, and non–trauma-exposed Kurdish refugees indicated reduced gray matter volumes in the cingulate and orbitofrontal cortices, wherein the non–trauma-exposed individuals had higher volumes compared with the exposed groups, and volumetric deficits were associated with trauma exposure. Refugee-related trauma has been shown to affect not only brain structure and function but also postmigration stress: One study of predominantly Iraqi and Iranian refugees resettled in Australia found that cumulative trauma and postmigration stress were associated with fear-related regional activity and connectivity. Interestingly, the authors found that postmigration stress was positively associated with connectivity within facial perception networks; such enhanced activation may interrupt interpersonal appraisal and may affect postsettlement adjustment. Familial and community-based interventions that foster interpersonal growth may be beneficial in the context of these findings, and both the finding and its implications may have relevance not only to refugee groups, but also to other migrant and displaced populations. Neuroimaging data from the same time also have indicated that “considering social attachments in refugees could be important to posttrauma recovery, based within changes in key emotion regulation brain systems”. In addition to emotion regulation, refugees may also exhibit variant reward-related function. In a sample of refugees predominantly from the Middle East/North Africa region, those with PTSD exhibited reduced prefrontal responses to reward compared with healthy volunteers, and this was associated with greater severity of anhedonia. These findings highlight reward processing as another potential novel treatment target for refugees who experience PTSD and depression.

While neuroimaging studies can provide insightful information, the method is costly and less accessible. In recent years, levels of pro- and anti-inflammatory cytokines and acute-phase proteins have been queried as candidate biomarkers of PTSD and other trauma-related disorders in veterans and the general population. Given that inflammatory markers can be easily and rapidly obtained and measured in blood and saliva samples, they could potentially inform resource allocation, inform clinical care, and track treatment efficacy in a cost-effective and accessible, objective manner. Indeed, several studies have queried inflammation as an indicator of physical health conditions in refugees, but fewer have looked at mental health despite evidence of physiological changes—like cortisol dysregulation—in refugees. While much of the literature points toward a positive association between inflammation and severity of symptoms, some studies indicate a negative or no relation. Notably, research with Middle Eastern refugee populations from our team and others has failed to identify significant correlations between inflammation and symptoms; the same was true in a cohort of female refugees from North Korea. However, one study did show a significant association between C-reactive protein and both PTSD and depression. Another team previously reported lower levels of C-reactive protein and serum amyloid A in Iraqi refugees with PTSD compared with those without. Such variation may be due to the types of trauma exposure, time since exposure, sex differences, additional environmental exposures, and genetic ancestry. Ancestral variation in immune-related genes has been identified in predominantly European and some African ancestry samples. However, the lack of representation of non-European individuals in genome-wide association studies (78% of individuals in genome-wide association studies are of European ancestry; 10% are Asian, 2% are African, and 1% are Hispanic or Latin American, with the least represented groups being of Native American and Middle Eastern ancestry) not only hinders researchers from calculating polygenic risk scores in non-European samples, but also presents a gap in the knowledge base of how genetic variation may underlie differences in immune regulation. Similarly, genetic variation may underlie differences in sympathetic, hypothalamic-pituitary-adrenal axis, and hormonal systems that could contribute to differential findings across individuals of different backgrounds—including Indigenous and displaced populations. As can be seen, the lack of representation in genetics research has wide-reaching consequences and leaves a number of scientific questions outstanding. This problem expands beyond the study of displaced populations, and there are several calls—including current ones from the National Institute of Mental Health—to improve this.

Like inflammation, psychophysiological measures may be viable candidate biomarkers worthy of consideration in displaced populations, especially features like acoustic startle response, fear-potentiated startle, and skin conductance response to trauma interview, as well as those commonly obtained as part of routine clinical care like blood pressure, heart rate (HR), and HR variability. HR is considered one of the most robust physiological indices of PTSD. One study of Iraqi refugees found higher HR across all refugees regardless of diagnostic status compared with healthy control participants; however, the authors did not observe specificity for PTSD (and it should be noted that all refugees in the study screened positive for at least one mental disorder). A similar finding was observed in a sample of Cambodian refugees; however, in this sample, those with PTSD demonstrated the greatest elevations in HR, and the same sample also exhibited elevations in skin conductance and blood pressure. In another study of refugees with PTSD, the acoustic startle response was associated with greater severity of PTSD and lower levels of functioning (84). Finally, an electrophysiology study in trauma+ PTSD+, trauma+ PTSD−, and trauma− PTSD− Iraqi refugees indicated reduced auditory and visual responses in the PTSD+ group compared with non–trauma-exposed control subjects. Psychophysiological studies with refugees that have failed to produce significant results may have been limited by small sample sizes and problems related to the use of self-report measures of psychiatric symptoms for use in non-Western cohorts. Even in studies that have reported preliminary findings, results must be interpreted with caution given insufficiently powered analyses. Psychophysiological studies are severely lacking in refugee populations, and displaced populations more broadly, yet psychophysiological biomarkers may be the most accessible and objective indicators of mental health in such a cohort. Current investigations in this realm are ongoing by the authors at the Stress, Trauma, and Anxiety Research Clinic (STARC lab).

What We Don’t Know

Gene-by-environment interactions largely underlie psychobiological phenotypes associated with mental health disorders, yet our current body of research in this realm is biased toward White cohorts in Western industrialized nations and therefore is unable to fully model key genetic and environmental factors, including culture, that underlie mental health. Recent advances in the field of cultural neuroscience have shown not only that mental illness presents differently between cultures, but also that the culture itself shapes the brain and affects how information is processed. Cumulative research indicates that people raised in different cultures process facial affect, contexts and cues, and interpersonal interactions differently, all of which are important and integral parts of a displaced person’s experience. Chiao and Blizinsky summarized “one of the most robust findings within cultural neuroscience” as prefrontal activity as a function of cultural values. Briefly, those who belong to individualistic cultures have greater prefrontal activity when thinking about themselves in general, while those who belong to collectivistic cultures have greater prefrontal activity when thinking about themselves in a contextual fashion, such as in relation to others. So too does the amygdala differentially respond to emotional cues across cultures, and this variation may change over time owing to prolonged exposure within a different culture. Notably, in Chiao and Blizinsky’s review of cultural neuroscience, no studies of prefrontal-amygdala circuitry in Middle Eastern, African, South Asian, Latino, or Indigenous populations were cited. There is a clear gap in research across global populations, and especially in regions from which a high number of people migrate or experience the impacts of forced displacement. While an important next step is to begin to learn how cultural and environmental variation in neurobiology contributes to differences in psychopathology, at least in the area of trauma and stress, it will be pivotal to address such differences among displaced populations of diverse backgrounds.

What makes this field even more complicated are the genetic differences in people of diverse ancestries. There has been enormous investment in recent years in understanding of the genetic and epigenetic characteristics of risk and resilience to mental illness. The Psychiatric Genomics Consortium has been one of several important initiatives that have attempted to include a diverse array of populations of different ancestries in a large dataset. However, there seems to be limited access to such data from displaced populations. For instance, to our understanding, the only sample of individuals of Middle Eastern ancestry included in the Psychiatric Genomics Consortium for PTSD comes from our group. The inclusion of people of different ancestries and diverse traumatic experiences in such research is vital in light of inclusivity and what we know from cultural neuroscience research about the role of genetic variation in the neurobiology of culture. An example is genetic distance, which indicates that geographic clusters may affect allele frequency. Here, not only does modeling the variation across populations become important for the environmental aspect of the gene-by-environment interaction (as described above), but also the relevance of conducting genetic studies across geographic regions becomes essential to fully understand the biological underpinnings of psychiatric disease.

Challenges in the Field

There are a number of factors that may contribute to the paucity of research at the intersection of neurobiology and displaced populations. Primarily, as an intrinsic function of their migratory status, some displaced populations may be difficult to access. While refugees and internally displaced persons may be more readily accessible when based at resettlement camps, postsettlement—largely in cities—it may be more difficult to meet such populations without close partnerships with representatives of and from displaced communities. Migration out of camps to resettlement contexts not only may complicate efforts to longitudinally track health, but also can result in a lack of uniform health services and disrupted access thereto. This also adds a layer of complexity in controlling for changes in the environment and additive environmental stressors in longitudinal studies and care. Additionally, both camps and other protracted displacement contexts are largely found in poor and unstable regions. This means that 1) infrastructure to meet both the research goals of investigators (e.g., there are no magnetic resonance imaging scanners in resettlement camps, inadequate funding) and the clinical needs of displaced persons may not be sufficient, and 2) relational, community, and societal-level factors may add additional burdens of discrimination, and lack of access to resources, education, and jobs, potentially furthering stress and psychopathology.

Once connected, building trust with displaced persons and ethical considerations are additional critical issues to consider. There may be social and legal concerns of participants that may deter participation for fear of retaliation, loss of services, or shame; may result in underreporting; or may put an individual at risk should privacy or confidentiality be breached. The ability to freely make informed consent may also be hindered, especially when conducting research in camps at which individual freedom and choice may have largely been curtailed and in situations in which individuals may be illiterate and hence unable to read and sign a consent form. Individuals may feel as though they are required to participate, or they may perceive research opportunities as their only option to contact a medical expert, given the striking provider shortages not only in conflict zones and resettlement camps, but also in host countries. Research with displaced populations must therefore be well focused and conducted, at least in part, by members from the beneficiary community—those who share not only the language, but also the culture and experiences, and who have a direct benefit for the target community. Community-based participatory research models offer a guiding framework to meet these goals.

Researchers and clinicians who intend to work with beneficiary communities of which they are not a part of should engage in cultural competency training, and teams should include members who originate from the beneficiary community. Existing data should be leveraged to the fullest extent and when necessary additional data collection be conducted in partnership with a strong local organization that works with beneficiary communities by individuals belonging to the beneficiary community. Adaptation of local mental health expressions and idioms into interventions and using locally derived measures is another potential solution. Here, there is an opportunity for novel research to generate the evidence base for participatory community-based approaches and psychometric studies of adapted versions (e.g., translations, culturally appropriate modifications) of standardized measures for assessing mental health and psychopathology.

Why Is It Important?

While most biological psychiatry research on trauma and cumulative stress is focused on military and urban civilian populations and those affected by poverty, there is much less known about the displaced populations with the combined experience of the aforementioned groups. Refugees and survivors of torture are civilians without military training or protection, who are uniquely exposed to 1) various levels of military trauma, 2) civilian interpersonal trauma, 3) poverty and environmental stress, and 4) often urban trauma and cumulative stress in the host countries. This is a unique population in that the experiences of displaced persons do not align with those of traumatized military or civilian groups. On the other hand, there are shared features between refugees and other traumatized groups, meaning that research on displaced persons could bring additional insight to research on other traumatized populations. Given that almost 1% of the world population has been forcibly displaced, dedication of research resources to understanding potential unique neurobiological impacts of trauma and stress in refugees is important from an equity and inclusiveness standpoint, and for our understanding of the neurobiology of trauma and stress in general. Additionally, eliminating health disparities that affect not only displaced persons, but also other underrepresented and marginalized groups could save the U.S. economy more than $1 trillion (about $3100 per person in the United States). Rigorous neuroscientific research in refugee populations could give rise to increased resource allocation, focused preventative interventions, and efficacious culturally adapted treatments. In the realm of health disparities, migratory groups are unique in that they may have experienced disparities attributed to different root causes across various contexts. Upon resettlement, they may experience health disparities owing not only to being a migrant population, but also to acculturative stress.

Another motivator to fill this knowledge gap is the importance of neurobiological findings in fighting stigma and in advocacy. Recently, the first author (AJ) participated in a documentary about Sudanese refugees as a refugee trauma expert. As part of this work, the producers aimed to show their audience that trauma affects the brain of a refugee, as it does a first responder, a veteran, and a civilian with PTSD, to allow the public the opportunity to understand the universality of trauma including in refugees. For that purpose, they asked for sample brain images of Middle Eastern or African refugee participants with PTSD. Unfortunately, there was not much of such data available in the literature. Availability of such information about neurobiology of trauma is helpful not only to the public, but also to the individuals who experience trauma and mental illness, to develop insight into what happens in a traumatized and stressed brain. Having a knowledge base about the biological bases of mental illness can help to overcome stigma by contextualizing mental illness as being the same as any other illness of the body, which would not be met with such stigmatization, and can contribute to public education on these matters. This is specifically important because such stigma often contributes to initial resistance in seeking and accepting treatment. This could also help in acceptance of medical treatments such as pharmacotherapy. Of course, there is conflicting evidence that neurobiologically based educational interventions might actually increase stigma; social contact–based interventions may offer an alternative in this case to beneficially reduce stigma in mental health.

Finally, and related to the previous topic, it is important to not lose sight of a primary goal of research in biological psychiatry: to inform prevention and treatment. A key aspect of personalized treatment in recent years has been determining biomarkers of etiology, course, and severity of psychiatric symptoms for prevention, focused intervention, and neurobiological determinants of treatment effects. From a clinical standpoint, cultural differences in the conceptualization of mental health as an illness, language barriers, and the unique traumas and stressors experienced by displaced persons necessitate rethinking treatment and customizing treatments that are more acceptable, feasible, and effective in these populations. What biological psychiatry can contribute to this field is the expansion of biomarker research in displaced populations. Furthermore, large-scale clinical trials of pharmacological interventions for stress- and trauma-related disorders and depression often do not include participants with ancestries and cultures of many of the refugee and immigrant populations. Mollica wrote that “special attention must be given to the proper dosing of psychotropic drugs in culturally diverse populations.” Genetic and metabolic differences in these populations might lead to different response, tolerance, and side effect profiles for medications commonly used in Western medicine, which is corroborated by peer-reviewed research on cultural factors related to the use of psychotropic medications. More research is needed here to parse out the genetic, metabolic, cultural, and psychological contributors to variance in response to medication in diverse populations.

Call to Action: How to Get There

War, natural disasters, persecution, and migration (forced or voluntary) have continued to mark human history. This has resulted in increased rates of PTSD and other mental health conditions in forcibly displaced persons compared with those of the general population. Refugees and migrants have unique experiences and cultural, environmental, and genetic backgrounds, and they are affected by health disparities that may distinguish them from populations traditionally featured in neuroscientific studies—namely, WEIRD (Western, educated, industrialized, rich, and democratic) samples. Understanding the unique experiences of these individuals and their communities within the greater society is critical to ensuring their representation in scientific research and identifying mechanisms of intervention across all levels of the ecological systems model. The paucity of data here limits the ability to fully understand the neurobiological processes underlying mental health in displaced populations, which extends to a diminished ability to develop and evaluate focused prevention and treatment. To begin to achieve this goal, we provide recommendations herein.

Researchers in this field should consider focused research questions regarding displaced populations. As noted above, most research in migrant and refugee populations is focused on epidemiological and environmental questions, while neuroscience research is lacking. The inclusion of such populations in biological psychiatry can be encouraged by 1) education on these groups and the significance of this research; 2) targeted funding allocated to such research by the National Institutes of Health, National Science Foundation, and others; and 3) focus on displaced populations at national and international conferences, as well as in related high-impact journals. This may include inviting those involved in refugee and migrant research to these venues and connecting them with neuroscience and biological researchers, specifically in areas of trauma and stress. Many research collaborations start in such contexts.

Related to the previous point, there is a need for providing resources and expertise in regions that host larger numbers of refugees. For instance, while most Syrian and Iraqi refugees are resettled in neighboring countries in the Middle East, neurobiological research resources are not as available and expansive in these countries as they are in the United States, for example. Efforts to connect research teams across the globe will not only help fill these gaps in resources and skills, but also strengthen and expedite research for all involved via merging forces and resources. This may be fostered by funding opportunities from the Fogarty International Center at the National Institutes of Health, the Fulbright Scholar Program, and other major funding centers with capability and involvement in international research.

Neuroscientific research in host countries should use assessment tools for measuring stress and mental health concerns that have been adapted, validated, and found to be reliable and feasible across cultures. There should be special attention paid to cultural sensitivities. For instance, our experience suggests that a person's cultural background might affect their level of comfort or acceptance with questions about their history of sexual experiences or trauma. Researchers should also assess stress and trauma related to displacement and discrimination to capture the unique experiences of displaced populations. Mixed methods approaches may be especially useful here. Cultural neuroscience studies can consider differences among persons from geographically proximal locations: Despite proximity and even shared ethnicity, communities may have variant cultural practices. Research in one displaced population might not necessarily generalize to others. Neuroscientific research with forcibly displaced populations should be framed within community-based participatory action research models. This must begin with building a trusting rapport with members of the target community and their trusted leaders, and inclusion of members of the community as equal members of the research team. The research should be informed by the needs of community members, and the results of the research should be available to community members for their knowledge, feeling of being truly included, and advocacy. Integrating stakeholders into the research team can ensure adequate recruitment and full representation and bolster success. Our team’s research has enormously benefited from these strategies of working with the community and using the help of those trusted by the refugee communities. The inclusion of people who share the same background with the target population in the research team is also of vital significance. Our projects have benefited immensely from the inclusion of research team members who are refugees or first-generation immigrants themselves.

Researchers working with displaced populations should also consider how to execute rigorous science across diverse settings: Structural barriers including geographic distance, transportation, Wi-Fi, and access to communication devices may limit participation for displaced persons. The use of mobile technologies for data collection in nonlaboratory environments can further the inclusion of broader populations.

Finally, given the ongoing nature of the trauma and stress among the refugee and migrant population, research in these groups not only has to consider the variety of environmental and cultural factors of risk and resilience, but also should consider a longitudinal approach to understanding the neurobiology of stress and trauma in them. The traditional approach of seeing PTSD as a dichotomous variable, in which individuals either have or do not have a certain condition, in cross-sectional studies might not be as informative in all populations, specifically in displaced persons. Based on their current level of environmental stress and trauma, the same person might pass the full diagnostic criteria for PTSD at one time point (and in a simplistic approach be considered as traumatized PTSD) and not at another time point (and be considered trauma-exposed resilient). For this reason, and for a better understanding of the most important predictors of risk and resilience and biological and environmental targets of intervention, longitudinal studies in refugee and migrant populations are of vital significance.

Despite the chronic and cumulative stressors and traumas faced by displaced populations, these communities are incredibly resilient. Capturing facets of resilience in such groups will be informative for the treatment of those more affected by trauma and stress. While there is much more work to be done, efforts toward modeling the experiences of diverse populations continue to expand and will prove to be transformative to the field of biological psychiatry.

Summary

Many people worldwide are forced to leave their homes due to various difficult situations. These include war, violence, human rights abuses, and natural disasters. The United Nations reported in 2020 that about 1% of the global population, or 1 in 95 people, are in this situation. These individuals are categorized as internally displaced people, refugees, or asylum-seekers. Internally displaced people stay within their home country, while refugees have crossed international borders seeking safety. Asylum-seekers have left their country but have not yet received legal recognition as refugees. These groups are different from migrants, who move for reasons like work, study, family, or to escape poverty. However, both displaced persons and migrants can face significant dangers and stress.

Many forcibly displaced individuals experience severe trauma, such as war, loss of loved ones, natural disasters, or assault. This trauma can lead to mental health issues like post-traumatic stress disorder (PTSD), anxiety, and depression. Difficulties after moving, such as discrimination, also contribute to these problems. For example, Syrian refugees may be ten times more likely to develop PTSD than the general public. Studies across various refugee groups show high rates of PTSD, anxiety, and depression. Beyond direct trauma, refugees often face ongoing stressors. These include a lack of basic healthcare, food, safety, and money. They also deal with being separated from their homes and loved ones, uncertainty about the future, cultural adjustment stress, changes in family roles, and prejudice in host countries. These stressors can last for years or decades.

Torture is the intentional act of causing severe pain or suffering to someone over whom the abuser has power, aiming to force a specific response. Torture has long-lasting physical and mental health effects. These can include memory problems, physical pain, feelings of shame, PTSD, depression, anxiety, confusion, and paranoia. These issues are often made worse by challenges after resettlement and long waits for medical help. Up to 88.3% of torture survivors may experience PTSD, 91% anxiety, and 94% depression. Survivors of torture often respond less well to common PTSD treatments, highlighting the need for better understanding and more effective interventions.

People who have been displaced, regardless of the reason, experience unique and extensive trauma and stress. This affects them as individuals, their families, their communities, and society. This article explores how neuroscience and biological psychiatry can help address mental health needs for those uprooted from their land. The focus is on refugee communities. The article examines the known biological effects of forced displacement trauma, identifies gaps in current research, and discusses challenges in this field. It also explains why addressing these gaps is important and offers recommendations for improving biological psychiatry research in this area.

What Is Known

Significant progress has been made in understanding how trauma and stress affect the brain and body. Many studies using brain imaging, genetics, hormone analysis, and physiological measurements have looked at these effects. However, most of this research has focused on military personnel and people in Western countries. In contrast, research on trauma and stress among refugees and migrants has largely focused on how common mental illnesses (especially PTSD) are and how environmental stressors contribute to mental health problems. Neuroscience researchers have been less involved in this area, and most studies are published in journals not focused on biology.

Few brain imaging studies have been conducted with refugees. One notable study involved traumatized North Korean refugees. It found that these refugees showed increased activity in brain regions like the amygdala and hippocampus when viewing negative images, compared to South Koreans without trauma. The refugee group also showed stronger connections between the prefrontal cortex, amygdala, and hippocampus during a task that involved controlling emotions. This increased connectivity was unexpected but might be due to refugees using emotion suppression as a coping strategy. This finding suggests that a person's environment can influence the brain processes related to mental health conditions. Another study of Kurdish refugees found that those exposed to trauma and with PTSD had less gray matter volume in certain brain areas compared to those without trauma. The study also found that cumulative trauma and stress after migration affected brain activity in ways related to fear. This suggests that community-based interventions that support interpersonal growth could be helpful. Other studies have shown that social connections are important for recovery after trauma and that refugees may have different brain responses related to reward. For example, refugees with PTSD showed reduced brain activity in reward pathways, which was linked to greater anhedonia (inability to feel pleasure). This highlights reward processing as a possible new treatment target for refugees with PTSD and depression.

While brain imaging provides valuable information, it is expensive and not widely available. In recent years, researchers have explored inflammatory markers (like cytokines and acute-phase proteins) as potential indicators for PTSD and other trauma-related disorders. These markers can be measured easily and affordably from blood and saliva. They could help guide resource allocation, clinical care, and track treatment effectiveness. Several studies have looked at inflammation as a marker for physical health in refugees, but fewer have examined its link to mental health, despite evidence of other physiological changes like hormone imbalances. While much of the research suggests a link between inflammation and symptom severity, some studies show a negative or no connection. Research with Middle Eastern and North Korean refugee populations has often not found significant links between inflammation and symptoms. However, one study did find a link between C-reactive protein and both PTSD and depression. Another study reported lower levels of certain inflammatory markers in Iraqi refugees with PTSD compared to those without. These varied findings might be due to differences in trauma types, time since trauma, sex, other environmental exposures, and genetic ancestry. Genetic differences related to the immune system exist across different populations. However, a lack of diversity in large genetic studies means that our understanding of how genes influence immune regulation, and therefore mental health, is incomplete, particularly for non-European groups. This gap also extends to other biological systems that influence mental health. Addressing this lack of representation in genetic research is crucial, as highlighted by various calls for improvement, including from the National Institute of Mental Health.

Like inflammation, physiological measurements could serve as important indicators for mental health in displaced populations. These include responses like acoustic startle, fear-potentiated startle, and skin conductance during trauma interviews. Routine clinical measures such as blood pressure and heart rate (HR) variability are also relevant. HR is considered a strong indicator of PTSD. One study of Iraqi refugees found higher HR across all refugees, regardless of their mental health diagnosis, compared to healthy individuals. Another study of Cambodian refugees found similar results, with those having PTSD showing the highest HR, along with increased skin conductance and blood pressure. Additionally, a study of refugees with PTSD showed that the acoustic startle response was linked to more severe PTSD symptoms and lower functioning. Electrophysiology studies in Iraqi refugees with PTSD have also shown reduced brain responses to sounds and visuals. Studies that have not found significant results in refugees may have been limited by small sample sizes or issues with using self-reported symptoms in non-Western groups. Even preliminary findings need careful interpretation due to insufficient statistical power. Psychophysiological studies are greatly needed in refugee and displaced populations, as these biomarkers could be accessible and objective indicators of mental health. Ongoing research is addressing these areas.

What Is Not Known

Interactions between genes and environment largely shape the biological and psychological traits associated with mental health conditions. However, current research is mostly focused on White populations in Western industrialized countries. This limits our ability to fully understand the genetic and environmental factors, including culture, that influence mental health. Recent studies in cultural neuroscience show that mental illness not only appears differently across cultures, but culture itself can shape the brain and how information is processed. Research indicates that people raised in different cultures process facial expressions, social cues, and interactions differently, all of which are vital to the experiences of displaced individuals. For example, individuals from individualistic cultures show more prefrontal brain activity when thinking about themselves in general, while those from collectivistic cultures show more activity when thinking about themselves in relation to others. The amygdala also responds differently to emotional cues across cultures, and this can change over time with prolonged exposure to a new culture. Importantly, many cultural neuroscience reviews lack studies on brain circuits in Middle Eastern, African, South Asian, Latino, or Indigenous populations. There is a clear research gap in global populations, especially in regions with high numbers of migrants or displaced people. A crucial next step is to understand how cultural and environmental differences in neurobiology contribute to varying mental health problems, particularly trauma and stress, among displaced populations from diverse backgrounds.

Adding to the complexity of this field are genetic differences among people of diverse ancestries. Significant investment has been made in recent years to understand the genetic and epigenetic factors linked to mental illness risk and resilience. Initiatives like the Psychiatric Genomics Consortium have aimed to include diverse populations in large datasets. However, access to data from displaced populations appears limited. For instance, the only Middle Eastern ancestry sample for PTSD in the Psychiatric Genomics Consortium comes from one research group. Including people from different ancestries and with diverse traumatic experiences in such research is crucial for inclusivity. It also aligns with cultural neuroscience findings about how genetic variation influences the neurobiology of culture. For example, genetic distance indicates that geographic groups may have different gene frequencies. This means that studying variation across populations is important not only for understanding environmental influences on gene-environment interactions, but also for conducting genetic studies across different geographic regions to fully understand the biological roots of mental illness.

Challenges in the Field

Several factors contribute to the limited research on neurobiology and displaced populations. One primary challenge is that some displaced groups can be difficult to reach due to their migratory status. While refugees and internally displaced persons in resettlement camps may be more accessible, it can be harder to connect with them after they move to cities, without strong partnerships with community representatives. Movement out of camps can make it difficult to track health over time and can disrupt access to consistent healthcare services. This also complicates efforts to control for environmental changes and new stressors in long-term studies. Additionally, many camps and long-term displacement areas are in poor and unstable regions. This means that there may be insufficient infrastructure for both research goals (e.g., no MRI scanners in camps, inadequate funding) and the clinical needs of displaced persons. Furthermore, social, community, and societal factors can add burdens like discrimination and a lack of access to resources, education, and jobs, potentially worsening stress and mental health issues.

Once contact is made, building trust with displaced individuals and considering ethical concerns are critical. Participants may have social and legal worries that discourage participation, such as fear of retaliation, losing services, or shame. This could lead to underreporting or put individuals at risk if privacy is breached. The ability to give informed consent freely can also be challenging, especially in camps where personal freedom may be limited. People who are illiterate may not be able to read and sign consent forms. Individuals might feel pressured to participate or see research opportunities as their only way to access a medical expert, given severe shortages of providers in conflict zones, resettlement camps, and host countries. Therefore, research with displaced populations must be well-focused and conducted, at least in part, by members of the affected community. These individuals should share the language, culture, and experiences, and the research should directly benefit the target community. Community-based participatory research models offer a framework for achieving these goals.

Researchers and clinicians who plan to work with communities they are not a part of should receive cultural competency training, and teams should include members from the beneficiary community. Existing data should be used to its fullest extent. If new data collection is necessary, it should be done in partnership with a strong local organization that works with beneficiary communities, and by individuals who are part of that community. Adapting local expressions and terms for mental health into interventions and using locally developed measures is another solution. This presents an opportunity for new research to build evidence for community-based approaches and to study the effectiveness of culturally adapted versions of standard mental health assessment tools.

It is also important for researchers working with displaced populations to consider how to conduct rigorous science in various settings. Structural barriers like geographic distance, transportation, Wi-Fi, and access to communication devices can limit participation. Using mobile technology for data collection outside of laboratories can help include a wider range of people.

Finally, given the ongoing trauma and stress experienced by refugee and migrant populations, research in these groups must consider a longitudinal approach. This means studying them over time, taking into account various environmental and cultural factors related to risk and resilience. The traditional approach of only categorizing PTSD as present or absent in single-point-in-time studies may not be fully informative for displaced individuals. A person's changing environmental stress and trauma levels might mean they meet full PTSD diagnostic criteria at one time, but not at another. Therefore, longitudinal studies are crucial for understanding the most important predictors of risk and resilience, and for identifying biological and environmental targets for intervention.

Despite the many chronic stressors and traumas faced by displaced populations, these communities show incredible resilience. Understanding how these groups demonstrate resilience will be valuable for treating those more severely affected by trauma and stress. While much work remains, efforts to better understand the experiences of diverse populations are growing and will significantly advance the field of biological psychiatry.

Summary

Around one percent of the world's population, about 1 in 95 people, are forced to leave their homes. This is often due to persecution, human rights abuses, conflict, violence, or climate disasters. There are three main groups of forcibly displaced people: internally displaced people, refugees, and asylum-seekers. Internally displaced people move within their own country, while refugees flee their home countries due to conflict or persecution. Asylum-seekers have left their country seeking safety but have not yet been legally recognized as refugees. These groups are different from migrants, who leave their home countries for reasons like work, study, family, poverty, political unrest, violence, or natural disasters. Both forcibly displaced people and migrants may face significant dangers and stress in their home countries.

Many forcibly displaced individuals experience traumatic events such as war, losing loved ones, natural disasters, physical or sexual assault, fires, and explosions. These severe and ongoing traumas increase the risk of developing mental health conditions like post-traumatic stress disorder (PTSD), anxiety, and depression. Difficulties after displacement, such as discrimination, also contribute to these problems. For example, Syrian refugees may be ten times more likely to develop PTSD. Rates of PTSD, anxiety, and depression can be very high across various refugee groups, affecting many youths as well. Beyond trauma, refugees face ongoing stress from lack of basic healthcare, food, safety, and money, as well as separation from their environment and loved ones, uncertainty about the future, cultural adjustment stress, changes in family roles, and prejudice in host countries. These stressors can last for years or decades.

Torture involves the deliberate and severe infliction of pain or suffering by someone in power to get a specific response. It deeply affects both physical and mental health. Long-term effects can include memory problems, physical complaints, feelings of shame, PTSD, depression, anxiety, chronic pain, unclear speech, confusion, and paranoia. These issues are made worse by post-migration difficulties and long waits for medical services. Up to 88.3% of torture survivors may experience PTSD, 91% anxiety, and 94% depression. Survivors of torture often respond less effectively to standard PTSD treatments compared to other trauma-exposed groups, highlighting the need for better understanding and more effective interventions.

Regardless of why they are displaced, these groups have experienced a wide and unique range of trauma and chronic stress at individual, family, community, and societal levels. This article examines how neuroscience and biological psychiatry can help address mental health inequities for uprooted individuals, focusing on refugee communities. It reviews the biological impacts of trauma and stress from forced displacement, points out gaps in research, discusses challenges in the field, explains why addressing these challenges is important, and provides recommendations for improving biological psychiatry research in this area.

What Is Known

In recent decades, there have been significant advancements in understanding how trauma and stress affect the brain and body at a biological level. Many studies have explored these effects using neuroimaging, genetic and epigenetic analysis, neuroendocrine measures, and psychophysiological methods. However, most of this research has focused on military populations and Western countries. Research on trauma and stress in refugees and migrants has primarily looked at how common mental illnesses (especially PTSD) are and how environmental stressors contribute to mental health problems. Neuroscience researchers have been less involved in this area, and most studies are published in journals that do not focus on biology.

Few neuroimaging studies have been conducted with refugee groups. Notable research on traumatized North Korean refugees found that those exposed to trauma showed increased activity in the amygdala and hippocampus when viewing negative images, compared to South Korean volunteers who had not experienced trauma. The refugee group also showed greater connectivity between the prefrontal cortex, amygdala, and hippocampus during an emotion regulation task. In the refugee group, hippocampal activity was linked to PTSD symptoms. While increased amygdala and hippocampal activity in response to negative images is consistent with existing research, the finding of increased connectivity in emotion regulation areas was not. The authors suggested this might be because refugees use emotion suppression as a coping mechanism due to their past experiences. This finding supports the idea that environmental factors can influence the biological processes underlying psychiatric conditions, with potential implications for treatment.

Another study on Kurdish refugees, some with and without PTSD after trauma exposure, and some without trauma exposure, found reduced gray matter volumes in areas of the brain involved in emotion and decision-making (cingulate and orbitofrontal cortices) in the trauma-exposed groups. Those without trauma exposure had larger volumes in these areas, and the volume deficits were linked to trauma exposure. Research has shown that trauma related to being a refugee affects not only brain structure and function but also stress experienced after migration. For example, a study of primarily Iraqi and Iranian refugees in Australia found that ongoing trauma and post-migration stress were linked to brain activity and connectivity related to fear. Interestingly, the study also found that post-migration stress was positively associated with connectivity within facial perception networks. This increased activation might interfere with how people interpret social cues and could affect their adjustment after resettlement. This suggests that interventions focused on family and community, which promote interpersonal growth, could be helpful. These findings may be relevant to refugees and other displaced populations. Neuroimaging data also indicate that considering social connections in refugees could be important for recovery after trauma, based on changes in key brain systems involved in emotion regulation.

In addition to emotion regulation, refugees may also show differences in how their brains respond to rewards. In a group of refugees mostly from the Middle East/North Africa region, those with PTSD showed less activity in the prefrontal cortex in response to rewards compared to healthy volunteers. This was linked to more severe anhedonia (loss of pleasure). These findings suggest that reward processing could be a new target for treating PTSD and depression in refugees.

While neuroimaging studies provide valuable insights, they are expensive and often not easily accessible. Recently, researchers have explored levels of inflammation markers (such as pro- and anti-inflammatory cytokines and acute-phase proteins) as potential indicators for PTSD and other trauma-related disorders in veterans and the general population. Since these markers can be measured quickly and easily from blood and saliva, they could potentially help in allocating resources, guiding clinical care, and tracking treatment effectiveness in a cost-effective and objective way. Although several studies have examined inflammation as an indicator of physical health in refugees, fewer have looked at mental health, despite evidence of physiological changes like disrupted cortisol levels in refugees. Much of the research suggests a positive link between inflammation and symptom severity, but some studies show no relation or a negative one. Notably, research with Middle Eastern refugee populations, including from our team, has not found significant links between inflammation and symptoms. The same was true for a group of North Korean female refugees. However, one study did find a significant association between C-reactive protein and both PTSD and depression. Another team reported lower levels of C-reactive protein and serum amyloid A in Iraqi refugees with PTSD compared to those without. These varied findings might be due to differences in types of trauma exposure, time since exposure, sex, other environmental exposures, and genetic background.

Genetic variations related to the immune system have been identified mostly in people of European and some African descent. However, the lack of representation of non-European individuals in large-scale genetic studies (78% European, 10% Asian, 2% African, 1% Hispanic/Latin American, with Native American and Middle Eastern ancestries being the least represented) hinders the ability to calculate genetic risk scores in these groups. This also creates gaps in understanding how genetic variations affect immune regulation. Similarly, genetic variations may underlie differences in sympathetic nervous system, stress hormone (hypothalamic-pituitary-adrenal axis), and hormonal systems, which could explain differing findings across people from various backgrounds, including Indigenous and displaced populations. The lack of diversity in genetics research has broad consequences and leaves many scientific questions unanswered. This issue extends beyond the study of displaced populations, and there are ongoing calls, including from the National Institute of Mental Health, to improve representation.

Like inflammation markers, psychophysiological measures could be useful as biomarkers in displaced populations. These include responses like acoustic startle, fear-potentiated startle, and skin conductance response during trauma interviews. Routine clinical measures like blood pressure, heart rate (HR), and HR variability are also relevant. Heart rate is considered a strong physiological indicator for PTSD. A study of Iraqi refugees found higher HR in all refugees, regardless of their diagnosis, compared to healthy controls, though it didn't specifically identify PTSD (all refugees in that study screened positive for at least one mental disorder). A similar finding was seen in Cambodian refugees, but in this group, those with PTSD had the highest HR, as well as elevated skin conductance and blood pressure. Another study of refugees with PTSD showed that a stronger acoustic startle response was linked to more severe PTSD symptoms and lower functioning. Finally, an electrophysiology study in Iraqi refugees with and without PTSD after trauma exposure, and those without trauma exposure, showed reduced auditory and visual responses in the PTSD group compared to controls. Psychophysiological studies with refugees that have not found significant results may have been limited by small sample sizes and issues with using self-reported psychiatric symptoms in non-Western groups. Even studies with preliminary findings require careful interpretation due to insufficient statistical power. Psychophysiological studies are severely lacking in refugee and broader displaced populations, yet these biomarkers could be the most accessible and objective indicators of mental health in these groups. Ongoing research in this area is being conducted by the authors at the Stress, Trauma, and Anxiety Research Clinic (STARC lab).

What Is Not Known

Interactions between genes and the environment largely shape the biological and psychological traits associated with mental health disorders. However, current research in this area mostly focuses on White populations in Western industrialized nations. This limits its ability to fully capture key genetic and environmental factors, including culture, that influence mental health. Recent progress in cultural neuroscience shows that mental illness appears differently across cultures, and that culture itself shapes the brain and how information is processed. Research consistently indicates that people raised in different cultures process facial expressions, contexts, cues, and social interactions differently. These are all important aspects of a displaced person's experience.

Researchers Chiao and Blizinsky highlighted a key finding in cultural neuroscience: activity in the prefrontal cortex varies with cultural values. Specifically, people from individualistic cultures show more prefrontal activity when thinking about themselves generally, while those from collectivistic cultures show more activity when thinking about themselves in relation to others. Similarly, the amygdala responds differently to emotional cues across cultures, and this variation can change over time with prolonged exposure to a different culture. Importantly, Chiao and Blizinsky's review of cultural neuroscience did not cite any studies on prefrontal-amygdala circuitry in Middle Eastern, African, South Asian, Latino, or Indigenous populations. This reveals a clear gap in global research, especially in regions from which many people migrate or experience forced displacement. While it is important to understand how cultural and environmental differences in neurobiology contribute to variations in mental health problems, it is crucial to address these differences among displaced populations from diverse backgrounds, particularly in the context of trauma and stress.

Adding to the complexity of this field are the genetic differences among people of various ancestries. Significant investments have been made in recent years to understand the genetic and epigenetic factors linked to risk and resilience for mental illness. The Psychiatric Genomics Consortium is one important initiative that has aimed to include a diverse range of populations with different ancestries in a large dataset. However, access to such data from displaced populations appears limited. For instance, to our knowledge, the only sample of individuals of Middle Eastern ancestry included in the Psychiatric Genomics Consortium for PTSD comes from our research group. Including people of different ancestries and varied traumatic experiences in such research is vital for inclusivity and given what cultural neuroscience research tells us about the role of genetic variation in the neurobiology of culture. For example, genetic distance indicates that geographic clusters can affect gene frequencies. Therefore, it is important to consider variation across populations for the environmental aspect of gene-by-environment interactions, and genetic studies across different geographic regions are essential to fully understand the biological basis of psychiatric diseases.

Challenges in the Field

Several factors contribute to the scarcity of research at the intersection of neurobiology and displaced populations. A primary challenge is that some displaced groups can be difficult to reach due to their migratory status. While refugees and internally displaced persons in resettlement camps may be more accessible, it can be harder to connect with them once they resettle, often in cities, without strong partnerships with representatives from these communities. Moving from camps to resettlement areas can complicate efforts to track health over time and may lead to uneven or interrupted access to healthcare services. This also makes it harder to control for changes in the environment and additional stressors in long-term studies and care. Furthermore, both camps and other prolonged displacement situations are often located in poor and unstable regions. This means that infrastructure for research (e.g., lack of MRI scanners in camps, inadequate funding) and for meeting the clinical needs of displaced persons may be insufficient. Additionally, relational, community, and societal factors can add burdens like discrimination and lack of access to resources, education, and jobs, potentially worsening stress and mental health problems.

Once connected, building trust with displaced individuals and considering ethical issues are crucial. Participants may have social and legal concerns that deter participation, fearing retaliation, loss of services, or shame. This could lead to underreporting or put individuals at risk if privacy is breached. The ability to give informed consent freely can also be hindered, especially in camps where individual freedom may be limited, or if individuals are unable to read and sign consent forms due to illiteracy. Individuals might feel obligated to participate or see research opportunities as their only way to contact a medical expert, given the severe shortage of providers in conflict zones, resettlement camps, and host countries. Therefore, research with displaced populations must be well-designed and conducted, at least in part, by members from the beneficiary community—those who share language, culture, and experiences, and who directly benefit the target community. Community-based participatory research models offer a framework for achieving these goals.

Researchers and clinicians working with communities to which they do not belong should receive cultural competency training, and teams should include members from the beneficiary community. Existing data should be fully utilized, and if additional data collection is necessary, it should be done in partnership with a strong local organization that works with beneficiary communities, using individuals from those communities. Adapting local expressions and idioms related to mental health into interventions, and using locally developed measures, are other potential solutions. This presents an opportunity for new research to build evidence for participatory community-based approaches and for studies that test the reliability and validity of adapted (translated, culturally modified) versions of standard mental health assessment tools.

Why Is It Important?

Most biological psychiatry research on trauma and stress focuses on military personnel, urban civilians, and those affected by poverty. However, much less is known about displaced populations, who often experience a combination of these challenges. Refugees and torture survivors are civilians without military training or protection, uniquely exposed to military trauma, civilian interpersonal trauma, poverty and environmental stress, and often urban trauma and ongoing stress in host countries. This population is unique because their experiences do not align with those of traumatized military or civilian groups. Nevertheless, there are shared characteristics between refugees and other traumatized groups, meaning research on displaced individuals could offer new insights into trauma in other populations. Given that nearly 1% of the world's population is forcibly displaced, dedicating research resources to understanding the unique biological impacts of trauma and stress in refugees is important for promoting fairness and inclusivity, and for advancing our general understanding of the neurobiology of trauma and stress. Additionally, addressing health disparities that affect displaced persons and other underrepresented groups could save the U.S. economy over $1 trillion (roughly $3100 per person). Rigorous neuroscience research in refugee populations could lead to more resource allocation, targeted preventative interventions, and effective culturally adapted treatments. In terms of health disparities, migrant groups are unique because they may have experienced disparities with different root causes across various contexts. Upon resettlement, they may face health disparities not only due to being migrants but also due to stress from adapting to a new culture.

Another reason to address this knowledge gap is the importance of neurobiological findings in fighting stigma and in advocacy efforts. For example, a researcher (AJ) participated in a documentary about Sudanese refugees as an expert on refugee trauma. The producers aimed to show that trauma affects the brains of refugees, just as it affects first responders, veterans, and civilians with PTSD, to help the public understand the universal nature of trauma, including in refugees. For this purpose, they requested brain images from Middle Eastern or African refugee participants with PTSD. Unfortunately, very little such data was available in the literature. Having information about the neurobiology of trauma is helpful not only to the public but also to individuals experiencing trauma and mental illness, as it can help them understand what happens in a traumatized and stressed brain. A knowledge base about the biological foundations of mental illness can help overcome stigma by presenting mental illness as similar to any other physical illness, which typically does not face such stigmatization. This can also contribute to public education on these matters. This is particularly important because stigma often leads to initial resistance in seeking and accepting treatment. It could also aid in the acceptance of medical treatments like medication. Of course, there is conflicting evidence that neurobiologically based educational interventions might sometimes increase stigma; social contact-based interventions may offer an alternative in this case to effectively reduce mental health stigma.

Finally, and related to the previous point, it is crucial not to lose sight of a main goal of biological psychiatry research: to inform prevention and treatment. A key aspect of personalized treatment in recent years has been identifying biomarkers that indicate the cause, progression, and severity of psychiatric symptoms. This helps with prevention, targeted interventions, and understanding the biological factors influencing treatment effects. From a clinical perspective, cultural differences in how mental health is understood, language barriers, and the unique traumas and stressors experienced by displaced persons require a rethinking of treatment approaches. Treatments need to be customized to be more acceptable, practical, and effective for these populations. Biological psychiatry can contribute to this field by expanding biomarker research in displaced populations. Furthermore, large-scale clinical trials of medications for stress- and trauma-related disorders and depression often do not include participants from the diverse ancestries and cultures of many refugee and immigrant populations. Mollica emphasized that "special attention must be given to the proper dosing of psychotropic drugs in culturally diverse populations." Genetic and metabolic differences in these populations might lead to different responses, tolerance levels, and side effect profiles for medications commonly used in Western medicine. This is supported by peer-reviewed research on cultural factors related to the use of psychotropic medications. More research is needed to understand the genetic, metabolic, cultural, and psychological factors that contribute to differences in medication response in diverse populations.

Call to Action: How to Achieve These Goals

War, natural disasters, persecution, and migration (both forced and voluntary) continue to be features of human history. This has resulted in higher rates of PTSD and other mental health conditions in forcibly displaced people compared to the general population. Refugees and migrants have unique experiences and diverse cultural, environmental, and genetic backgrounds. They are also affected by health disparities that may set them apart from populations typically studied in neuroscience research—often described as WEIRD (Western, educated, industrialized, rich, and democratic) samples. Understanding the unique experiences of these individuals and their communities within the broader society is crucial for ensuring their representation in scientific research and for identifying intervention strategies at all levels of the ecological systems model. The lack of data in this area limits our ability to fully understand the biological processes underlying mental health in displaced populations. This, in turn, reduces our capacity to develop and evaluate focused prevention and treatment methods. To begin achieving this goal, we offer the following recommendations.

Researchers in this field should focus on specific research questions about displaced populations. As mentioned, most research on migrant and refugee groups focuses on epidemiology and environmental factors, while neuroscience research is lacking. Encouraging the inclusion of these populations in biological psychiatry can be done through: 1) educating people about these groups and the importance of this research; 2) allocating targeted funding for such research by organizations like the National Institutes of Health and National Science Foundation; and 3) highlighting displaced populations at national and international conferences and in high-impact journals. This could involve inviting researchers involved in refugee and migrant studies to these events and connecting them with neuroscience and biological researchers, particularly in the areas of trauma and stress. Many research collaborations begin in these types of settings.

Related to the previous point, there is a need to provide resources and expertise in regions that host large numbers of refugees. For example, while most Syrian and Iraqi refugees settle in neighboring Middle Eastern countries, neurobiological research resources are not as widely available or extensive in these countries as they are in places like the United States. Efforts to connect research teams globally will not only help fill these gaps in resources and skills but also strengthen and accelerate research for all involved by combining efforts and resources. This can be supported by funding opportunities from organizations like the Fogarty International Center at the National Institutes of Health, the Fulbright Scholar Program, and other major funding centers involved in international research.

Neuroscientific research in host countries should use assessment tools for measuring stress and mental health concerns that have been adapted, validated, and proven to be reliable and practical across different cultures. Special attention should be paid to cultural sensitivities. For example, our experience suggests that a person's cultural background might affect their comfort level or acceptance of questions about their sexual history or trauma. Researchers should also assess stress and trauma related to displacement and discrimination to capture the unique experiences of displaced populations. Mixed methods approaches can be particularly useful here. Cultural neuroscience studies can consider differences among people from geographically close locations: despite proximity and even shared ethnicity, communities may have different cultural practices. Research on one displaced population may not necessarily apply to others. Neuroscientific research with forcibly displaced populations should be framed within community-based participatory action research models. This must begin with building trusting relationships with members of the target community and their trusted leaders, and including community members as equal partners in the research team. The research should be guided by the needs of community members, and the results should be made available to them for their knowledge, to foster a sense of true inclusion, and for advocacy. Integrating stakeholders into the research team can ensure adequate recruitment, full representation, and boost success. Our team's research has greatly benefited from these strategies of working with the community and getting help from those trusted by refugee communities. Including people who share the same background as the target population in the research team is also vitally important. Our projects have benefited immensely from including research team members who are refugees or first-generation immigrants themselves.

Researchers working with displaced populations should also consider how to conduct rigorous science in diverse settings. Structural barriers such as geographic distance, transportation, Wi-Fi access, and availability of communication devices may limit participation for displaced individuals. Using mobile technologies for data collection in non-laboratory environments can increase the inclusion of broader populations.

Finally, given the ongoing nature of trauma and stress among refugee and migrant populations, research in these groups must consider the variety of environmental and cultural factors related to risk and resilience. It should also adopt a long-term approach to understanding the neurobiology of stress and trauma in these individuals. The traditional approach of viewing PTSD as a simple yes/no condition in single-point-in-time studies may not be as informative for all populations, especially displaced persons. Depending on their current level of environmental stress and trauma, the same person might meet the full diagnostic criteria for PTSD at one time (and be considered traumatized with PTSD) and not at another time (and be considered trauma-exposed and resilient). For this reason, and to better understand the most important predictors of risk and resilience, as well as biological and environmental targets for intervention, longitudinal studies in refugee and migrant populations are of vital importance.

Despite the ongoing and multiple stressors and traumas faced by displaced populations, these communities show incredible resilience. Capturing aspects of resilience in such groups will provide valuable information for treating those more affected by trauma and stress. While much more work is needed, efforts to model the experiences of diverse populations continue to grow and will prove transformative for the field of biological psychiatry.

Summary

Many people are forced to leave their homes because of violence, human rights abuses, and natural disasters. In 2020, about 1% of the global population, or 1 in 95 people, was displaced. These individuals are categorized as internally displaced people (staying within their home country), refugees (fleeing their home country), or asylum-seekers (seeking safety but not yet recognized as refugees). These groups are different from migrants, who move for reasons like work, study, or family, or to escape poverty or political unrest. Both displaced persons and migrants can face significant dangers and stress in their home countries.

Many displaced individuals experience deeply upsetting events, such as war, losing loved ones, or physical assault. These experiences, which can be severe and ongoing, increase the risk of mental health issues like post-traumatic stress disorder (PTSD), anxiety, and depression. Factors such as a lack of basic necessities, difficulty adjusting to a new country, discrimination, and harassment also worsen these problems. For instance, Syrian refugees may be ten times more likely to develop PTSD. Research on various refugee groups shows high rates of PTSD (13.9% to 83.4%), anxiety (16.7% to 90%), and depression (20% to 89%). Beyond single traumatic events, refugees face ongoing challenges before, during, and after displacement, including limited access to healthcare, food, and money, as well as separation from family, uncertainty, and prejudice in new countries.

Torture is defined as the deliberate infliction of severe pain or suffering to force a response from someone. Torture significantly impacts both physical and mental health, leading to long-term effects such as memory problems, physical complaints, feelings of shame, PTSD, depression, anxiety, and paranoia. These issues are often made worse by challenges in the new country and long waits for medical help. Up to 88.3% of torture survivors may develop PTSD, 91% anxiety, and 94% depression. Survivors of torture often respond less effectively to standard PTSD treatments, highlighting the need for better understanding and more targeted interventions.

Regardless of why people are displaced, they have experienced a wide range of trauma and ongoing stress affecting individuals, families, communities, and society. This article explores how neuroscience and biological psychiatry can improve mental health for displaced people, especially refugees. The focus includes reviewing the biological effects of trauma and stress from forced displacement, identifying gaps in current research, discussing challenges in this field, explaining why addressing these gaps is important, and recommending ways to improve biological psychiatry research in this area.

What Is Known

In recent decades, there have been significant advancements in understanding how trauma and stress affect the brain and body. Many studies using brain imaging, genetics, hormones, and physiological measures have looked at these effects. However, most of this research has focused on military personnel and Western populations. In contrast, studies on trauma and stress in refugees and migrants have mostly focused on how common mental illnesses are (especially PTSD) and how environmental stressors affect mental health. Neuroscience researchers have been less involved in this area, and these studies are often published in journals that do not specialize in biology.

Few studies have used brain imaging on refugee groups. Kim and colleagues published important findings from North Korean refugees who had experienced trauma. Their research showed that these refugees had increased activity in brain regions like the amygdala and hippocampus when looking at negative images, compared to South Korean volunteers without trauma. The refugees also showed stronger connections between the prefrontal cortex, amygdala, and hippocampus during a task that involved controlling emotions. In the refugee group, greater hippocampal activity was linked to more severe PTSD symptoms. While increased activity in the amygdala and hippocampus when seeing negative images matched existing research, the finding about increased connectivity between emotion-related brain regions was unexpected. The authors suggested this might be because refugees use strategies like suppressing emotions as a way to cope with their experiences. This finding supports the idea that environmental factors influence the biological brain processes linked to mental health conditions, which has implications for treatment.

Another study on Kurdish refugees with and without PTSD, who had experienced trauma, showed reduced gray matter volume in parts of the brain called the cingulate and orbitofrontal cortices. Individuals who had not experienced trauma had larger volumes in these areas, and the reduction in volume was linked to trauma exposure. Refugee-related trauma has been shown to affect not only brain structure and function, but also stress experienced after migrating. One study of mainly Iraqi and Iranian refugees in Australia found that cumulative trauma and post-migration stress were linked to brain activity and connections related to fear. Interestingly, this study also found that post-migration stress was positively linked to connectivity within facial perception networks. This enhanced activity might interfere with how people interpret social interactions and could affect their adjustment after settling. Interventions focused on family and community that promote social growth might be helpful given these findings. Both the findings and their implications could apply not only to refugee groups but also to other migrant and displaced populations. Brain imaging data from the same period also suggested that "considering social attachments in refugees could be important to post-trauma recovery, based within changes in key emotion regulation brain systems."

In addition to emotion regulation, refugees might also show different responses related to reward. In a group of refugees mostly from the Middle East/North Africa region, those with PTSD showed reduced brain responses in the prefrontal area to rewards compared to healthy volunteers. This was linked to more severe anhedonia (the inability to feel pleasure). These findings highlight how reward processing could be another new area for treating refugees experiencing PTSD and depression.

While brain imaging studies offer valuable insights, this method is expensive and not widely available. Recently, researchers have looked at levels of inflammatory markers (proteins that show inflammation) in the blood and saliva as possible indicators for PTSD and other trauma-related conditions in veterans and the general population. Since these markers can be measured easily and quickly, they could help guide resource allocation, clinical care, and track treatment effectiveness in a cost-effective and objective way. Many studies have explored inflammation as a sign of physical health issues in refugees, but fewer have looked at mental health, despite evidence of physiological changes—like abnormal cortisol levels—in refugees. While much of the research suggests a positive link between inflammation and symptom severity, some studies show a negative or no relationship. Notably, research on Middle Eastern refugee populations, including studies by our team, has not found significant links between inflammation and symptoms; the same was true for a group of North Korean female refugees. However, one study did find a significant link between C-reactive protein (an inflammatory marker) and both PTSD and depression. Another team reported lower levels of C-reactive protein and serum amyloid A in Iraqi refugees with PTSD compared to those without. These differences might be due to the types of trauma experienced, how long ago the trauma occurred, sex differences, other environmental exposures, and genetic ancestry.

Genetic variations related to immune genes have been identified mainly in people of European ancestry and some African ancestry. However, the lack of representation of non-European individuals in large genetic studies (78% are of European ancestry; 10% are Asian, 2% are African, and 1% are Hispanic or Latin American, with Native American and Middle Eastern ancestries being the least represented) not only makes it difficult to calculate genetic risk scores in non-European groups but also creates a gap in understanding how genetic variation might lead to differences in immune regulation. Similarly, genetic variation might explain differences in the sympathetic nervous system, the HPA axis (a central stress response system), and hormone systems, which could contribute to varying findings across people from different backgrounds, including Indigenous and displaced populations. As seen, the lack of diverse representation in genetics research has widespread consequences and leaves many scientific questions unanswered. This problem goes beyond the study of displaced populations, and there are several calls, including current ones from the National Institute of Mental Health, to improve this.

Like inflammation, physiological measurements—such as acoustic startle response, fear-potentiated startle, skin conductance response to trauma interviews, and routine clinical measures like blood pressure, heart rate (HR), and HR variability—could be useful indicators in displaced populations. Heart rate is considered one of the most reliable physiological signs of PTSD. One study of Iraqi refugees found that all refugees, regardless of their diagnosis, had higher heart rates compared to healthy control participants; however, the authors did not find that this was specific to PTSD (it should be noted that all refugees in the study screened positive for at least one mental disorder). A similar finding was observed in a group of Cambodian refugees; in this group, however, those with PTSD showed the greatest increases in heart rate, and the same group also had increased skin conductance and blood pressure. In another study of refugees with PTSD, the acoustic startle response was linked to more severe PTSD and lower levels of functioning. Finally, an electrophysiology study of Iraqi refugees with and without PTSD (both trauma-exposed and not trauma-exposed) showed reduced auditory and visual responses in the group with PTSD compared to control subjects who had not experienced trauma.

Psychophysiological studies with refugees that have not produced significant results may have been limited by small sample sizes and challenges related to using self-reported psychiatric symptoms in non-Western groups. Even in studies that have reported initial findings, results must be carefully considered due to analyses that may not have had enough statistical power. Psychophysiological studies are severely lacking in refugee populations, and displaced populations more broadly, yet psychophysiological biomarkers might be the most accessible and objective indicators of mental health in these groups. Current research in this area is being conducted by the authors at the Stress, Trauma, and Anxiety Research Clinic (STARC lab).

What Is Unknown

Interactions between genes and the environment largely determine the biological and psychological traits linked to mental health disorders. However, current research in this area mainly focuses on White populations in Western industrialized nations. This means it cannot fully explain key genetic and environmental factors, including culture, that influence mental health. Recent progress in cultural neuroscience shows not only that mental illness appears differently across cultures, but also that culture itself shapes the brain and how information is processed. Many studies indicate that people raised in different cultures process facial expressions, contexts, cues, and social interactions differently. All these are important parts of a displaced person's experience. Chiao and Blizinsky summarized "one of the most robust findings within cultural neuroscience" as prefrontal activity being related to cultural values. Simply put, people from individualistic cultures show more prefrontal activity when thinking about themselves generally, while those from collectivistic cultures show more prefrontal activity when thinking about themselves in a specific context, such as in relation to others. The amygdala also responds differently to emotional cues across cultures, and this variation can change over time due to long-term exposure to a different culture. Notably, in Chiao and Blizinsky's review of cultural neuroscience, no studies on the prefrontal-amygdala circuitry in Middle Eastern, African, South Asian, Latino, or Indigenous populations were mentioned. There is a clear gap in research across global populations, especially in regions from which many people migrate or experience forced displacement. While an important next step is to begin to learn how cultural and environmental differences in neurobiology contribute to variations in mental health problems, at least in the area of trauma and stress, it will be crucial to address these differences among displaced populations from diverse backgrounds.

Genetic differences among people from various ancestries further complicate this field. In recent years, there has been significant investment in understanding the genetic and epigenetic factors that contribute to mental illness risk and resilience. The Psychiatric Genomics Consortium is one of several important initiatives that has aimed to include diverse populations of different ancestries in a large dataset. However, access to such data from displaced populations appears limited. For instance, based on our understanding, the only sample of individuals of Middle Eastern ancestry included in the Psychiatric Genomics Consortium for PTSD comes from our research group. Including people from different ancestries and with diverse traumatic experiences in such research is vital for inclusivity and given what we know from cultural neuroscience research about the role of genetic variation in the neurobiology of culture. For example, genetic distance shows that geographic clusters can affect gene frequency. Here, not only is it important to model variation across populations for the environmental aspect of the gene-by-environment interaction (as described above), but also conducting genetic studies across different geographic regions becomes essential to fully understand the biological foundations of psychiatric disease.

Challenges in the Field

Several factors contribute to the scarcity of research at the intersection of neurobiology and displaced populations. A primary reason is that, by the very nature of their migration, some displaced populations can be difficult to access. While refugees and internally displaced persons might be more readily available when living in resettlement camps, it can be harder to connect with these groups after they settle—often in cities—without close partnerships with representatives from displaced communities. Moving out of camps into resettlement areas can complicate efforts to track health over time and can lead to uneven health services and disrupted access to care. This also makes it more complex to control for changes in the environment and additional stressors in long-term studies and care. Furthermore, both camps and other prolonged displacement situations are often located in poor and unstable regions. This means that 1) the infrastructure to meet both researchers' goals (e.g., no MRI scanners in camps, inadequate funding) and the clinical needs of displaced persons may be insufficient, and 2) relational, community, and societal factors can add further burdens of discrimination and lack of access to resources, education, and jobs, potentially worsening stress and mental health problems.

Once connections are made, building trust with displaced persons and addressing ethical considerations are crucial. Participants may have social and legal concerns that might prevent them from participating, due to fears of retaliation, losing services, or shame. This could also lead to underreporting or put individuals at risk if their privacy or confidentiality is breached. The ability to give informed consent freely might also be hindered, especially when conducting research in camps where individual freedom and choice may have been largely restricted, and in situations where individuals may be unable to read and sign a consent form due to illiteracy. Individuals might feel obligated to participate, or they might see research opportunities as their only way to contact a medical expert, given the severe shortage of providers not only in conflict zones and resettlement camps but also in host countries. Therefore, research with displaced populations must be well-focused and conducted, at least in part, by members from the beneficiary community—those who share not only the language but also the culture and experiences, and who directly benefit the target community. Community-based participatory research models offer a guiding framework to achieve these goals.

Researchers and clinicians who plan to work with communities they are not a part of should undergo cultural competency training, and teams should include members who come from the beneficiary community. Existing data should be used as much as possible, and when additional data collection is needed, it should be done in partnership with a strong local organization that works with beneficiary communities, by individuals belonging to that community. Adapting local mental health expressions and terms into interventions and using locally developed measures is another possible solution. This offers an opportunity for new research to build evidence for community-based participatory approaches and for studies that test the accuracy of adapted versions (e.g., translations, culturally appropriate changes) of standard measures for assessing mental health and mental illness.

Why Is It Important?

Most biological psychiatry research on trauma and ongoing stress focuses on military and urban civilian populations, as well as those affected by poverty. However, much less is known about displaced populations, who often experience a combination of these challenges. Refugees and torture survivors are civilians without military training or protection, uniquely exposed to 1) various levels of military-related trauma, 2) civilian interpersonal trauma, 3) poverty and environmental stress, and 4) often urban trauma and ongoing stress in their host countries. This is a distinct population because the experiences of displaced persons do not align with those of traumatized military or civilian groups. On the other hand, there are shared features between refugees and other traumatized groups, meaning that research on displaced persons could provide additional insights for research on other traumatized populations. Given that nearly 1% of the world's population has been forcibly displaced, dedicating research resources to understanding the unique biological impacts of trauma and stress in refugees is important from a fairness and inclusivity standpoint, and for our general understanding of the neurobiology of trauma and stress. Additionally, reducing health disparities that affect not only displaced persons but also other underrepresented and marginalized groups could save the U.S. economy over $1 trillion (about $3100 per person in the United States). Rigorous neuroscience research in refugee populations could lead to increased resource allocation, focused preventive interventions, and effective culturally adapted treatments. In terms of health disparities, migratory groups are unique because they may have experienced disparities due to different root causes across various settings. Upon resettlement, they may experience health disparities not only due to being a migrant population but also due to stress from adapting to a new culture.

Another reason to address this knowledge gap is the important role that neurobiological findings play in fighting stigma and in advocacy. Recently, the first author (AJ) participated in a documentary about Sudanese refugees as an expert in refugee trauma. As part of this work, the producers aimed to show their audience that trauma affects the brain of a refugee, just as it affects a first responder, a veteran, and a civilian with PTSD, to help the public understand that trauma is a universal experience, including for refugees. For this purpose, they requested sample brain images of Middle Eastern or African refugee participants with PTSD. Unfortunately, there was not much such data available in the literature. The availability of this kind of information about the neurobiology of trauma is helpful not only to the public but also to individuals experiencing trauma and mental illness, allowing them to understand what happens in a traumatized and stressed brain. Having a knowledge base about the biological foundations of mental illness can help overcome stigma by presenting mental illness as similar to any other physical illness, which would not be met with such stigmatization, and can contribute to public education on these matters. This is especially important because such stigma often leads to initial resistance in seeking and accepting treatment. This could also help in the acceptance of medical treatments like pharmacotherapy. Of course, there is conflicting evidence that neurobiologically based educational interventions might actually increase stigma; social contact–based interventions may offer an alternative in this case to beneficially reduce stigma in mental health.

Finally, and related to the previous point, it is important to remember a main goal of research in biological psychiatry: to inform prevention and treatment. A key aspect of personalized treatment in recent years has been identifying biological markers of the origin, course, and severity of psychiatric symptoms for prevention, focused intervention, and biological factors that determine treatment effects. From a clinical perspective, cultural differences in how mental health is understood as an illness, language barriers, and the unique traumas and stressors experienced by displaced persons make it necessary to rethink and customize treatments to be more acceptable, practical, and effective for these populations. What biological psychiatry can contribute to this field is the expansion of research on biological markers in displaced populations. Furthermore, large-scale clinical trials of medications for stress- and trauma-related disorders and depression often do not include participants from the ancestries and cultures of many refugee and immigrant populations. Mollica wrote that "special attention must be given to the proper dosing of psychotropic drugs in culturally diverse populations." Genetic and metabolic differences in these populations might lead to different responses, tolerance levels, and side effect profiles for medications commonly used in Western medicine, which is supported by research on cultural factors related to the use of psychotropic medications. More research is needed here to sort out the genetic, metabolic, cultural, and psychological factors that contribute to variations in medication response in diverse populations.

Call to Action: How to Achieve This

War, natural disasters, persecution, and forced or voluntary migration have always been part of human history. This has led to higher rates of PTSD and other mental health conditions in forcibly displaced persons compared to the general population. Refugees and migrants have unique experiences and cultural, environmental, and genetic backgrounds, and they are affected by health disparities that may distinguish them from populations traditionally studied in neuroscience—often referred to as WEIRD (Western, educated, industrialized, rich, and democratic) samples. Understanding the unique experiences of these individuals and their communities within the larger society is crucial for ensuring their representation in scientific research and for identifying intervention strategies at all levels of the ecological systems model. The limited data available hinders the ability to fully understand the neurobiological processes underlying mental health in displaced populations, which in turn limits the ability to develop and evaluate focused prevention and treatment. To begin to achieve this goal, we offer recommendations here.

Researchers in this field should focus their research questions on displaced populations. As noted, most research on migrant and refugee populations focuses on epidemiology and environmental factors, with neuroscience research being limited. Including these populations in biological psychiatry can be encouraged by 1) educating people about these groups and the importance of this research; 2) providing targeted funding for such research from organizations like the National Institutes of Health and National Science Foundation; and 3) highlighting displaced populations at national and international conferences, as well as in relevant high-impact journals. This could involve inviting those involved in refugee and migrant research to these events and connecting them with neuroscience and biological researchers, particularly in the areas of trauma and stress. Many research collaborations start in such contexts.

Related to the previous point, there is a need to provide resources and expertise in regions that host large numbers of refugees. For instance, while most Syrian and Iraqi refugees are resettled in neighboring countries in the Middle East, neurobiological research resources are not as available or extensive in these countries as they are in the United States, for example. Efforts to connect research teams across the globe will not only help fill these gaps in resources and skills but also strengthen and accelerate research for everyone involved by combining efforts and resources. This could be supported by funding opportunities from the Fogarty International Center at the National Institutes of Health, the Fulbright Scholar Program, and other major funding centers involved in international research.

Neuroscientific research in host countries should use assessment tools for measuring stress and mental health concerns that have been adapted, tested, and found to be reliable and practical across cultures. Special attention should be given to cultural sensitivities. For example, our experience suggests that a person's cultural background might affect their comfort or acceptance with questions about their sexual history or trauma. Researchers should also assess stress and trauma related to displacement and discrimination to capture the unique experiences of displaced populations. Mixed methods approaches (combining quantitative and qualitative data) can be particularly useful here. Cultural neuroscience studies can consider differences among people from geographically close locations: Despite proximity and even shared ethnicity, communities may have different cultural practices. Research on one displaced population might not necessarily apply to others. Neuroscientific research with forcibly displaced populations should be structured within community-based participatory action research models. This must begin with building trusting relationships with members of the target community and their trusted leaders, and including community members as equal partners on the research team. The research should be informed by the needs of community members, and the results of the research should be available to community members for their knowledge, sense of true inclusion, and advocacy. Integrating stakeholders into the research team can ensure adequate recruitment and full representation and boost success. Our team's research has greatly benefited from these strategies of working with the community and using the help of those trusted by refugee communities. The inclusion of people who share the same background as the target population in the research team is also vitally important. Our projects have benefited immensely from the inclusion of research team members who are refugees or first-generation immigrants themselves.

Researchers working with displaced populations should also consider how to conduct rigorous science in various settings: Structural barriers such as geographic distance, transportation, Wi-Fi, and access to communication devices can limit participation for displaced persons. Using mobile technologies for data collection outside of laboratory environments can further include a broader range of populations.

Finally, given the ongoing nature of trauma and stress among refugee and migrant populations, research in these groups must not only consider the variety of environmental and cultural factors related to risk and resilience but also adopt a long-term approach to understanding the neurobiology of stress and trauma in them. The traditional approach of viewing PTSD as a simple yes/no condition in cross-sectional studies might not be as informative for all populations, especially displaced persons. Based on their current level of environmental stress and trauma, the same person might meet the full diagnostic criteria for PTSD at one point (and be considered traumatized PTSD in a simplistic view) and not at another point (and be considered trauma-exposed resilient). For this reason, and for a better understanding of the most important predictors of risk and resilience and biological and environmental targets for intervention, long-term studies in refugee and migrant populations are of vital importance.

Despite the chronic and cumulative stressors and traumas faced by displaced populations, these communities show incredible resilience. Capturing aspects of resilience in these groups will be informative for treating those more affected by trauma and stress. While much more work needs to be done, efforts to model the experiences of diverse populations continue to expand and will prove transformative for the field of biological psychiatry.

Summary

Many people in the world are forced to leave their homes. This happens because of war, violence, unfair treatment, or big storms and other natural problems. The United Nations says there are three groups of these people:

• Internally displaced people: These people move to a different part of their own country but do not cross a border.

• Refugees: These people leave their home country to find safety in another country.

• Asylum-seekers: These people have left their country to find safety, but they are not yet officially recognized as refugees.

These groups are different from people who choose to move for work, school, or family reasons. But even people who choose to move can face dangers and stress in their home countries.

Many people who are forced to move have gone through very bad events. This can include war, losing loved ones, natural disasters, or being hurt. These hard experiences can lead to problems like post-traumatic stress disorder (PTSD), feeling worried or sad, and other health issues. They also face challenges like being treated badly or having trouble settling into a new place. For example, some studies show that Syrian refugees are much more likely to have PTSD than other people. People who have been tortured often have long-lasting physical and mental problems, like memory issues, pain, and confusion. They can also have PTSD, anxiety, and depression.

No matter why people are forced to move, they have gone through many difficult things. This article will look at how brain science and mental health studies can help these groups. We will focus on refugees, as this is where our knowledge is strongest.

What We Know

In recent years, we have learned a lot about how trauma and stress affect the brain and body. Many studies have looked at these effects. However, most of these studies have focused on soldiers or people in Western countries. There has not been as much research on refugees and migrants in this area. Most studies about refugees have looked at how many people have mental health problems, especially PTSD, and how their environment causes these problems.

There are only a few brain studies on refugees. One study looked at North Korean refugees who had experienced trauma. It found that their brains reacted more strongly to sad pictures compared to people who had not gone through trauma. These refugees also showed different brain connections when trying to manage their feelings. This suggests that their past experiences might have changed how their brains work. Another study on Kurdish refugees found that trauma changed parts of their brains. These findings show that trauma from being a refugee can affect how the brain works and how people deal with stress after moving.

Brain scans can give helpful information, but they cost a lot of money and are not always available. Other ways to measure health, like checking levels of certain things in blood or saliva, might be easier and cheaper. These checks could help doctors understand mental health problems and see if treatments are working. Some studies have looked at these kinds of measurements in refugees, but more research is needed to see how they relate to mental health problems like PTSD and depression. It is also important to know that genetic differences between people from different parts of the world can change how these measurements look. Many studies on genes have not included enough people from diverse backgrounds, which makes it harder to understand these differences.

Checking things like heart rate and how skin reacts to stress can also be helpful. These physical signs can show how the body is responding to trauma. For example, some studies have found that refugees, especially those with PTSD, tend to have higher heart rates. More research is needed in this area, but these simple tests could be a good way to understand the mental health of displaced people.

What We Don’t Know

Our understanding of mental health problems is often based on studies of people from Western countries. This means we do not fully understand how different genes and life experiences, including culture, affect mental health in other groups. Studies have shown that people from different cultures process information and emotions differently. For example, people from cultures that value individuals more may use a different part of their brain when thinking about themselves compared to people from cultures that value community. These cultural differences are important because they shape how a displaced person experiences the world. However, there is not enough research on these brain differences in people from many parts of the world, especially places where many people are forced to move.

Understanding genetic differences in people from various backgrounds is also important but complex. There has been a lot of work to understand how genes play a role in mental illness. However, there is not much genetic information from displaced people. It is very important to include people from different backgrounds and with different experiences in these studies. This will help us understand how genes and culture work together to affect mental health.

Challenges in the Field

It can be hard to do research on brain science and displaced people for many reasons. First, it can be difficult to reach people who are constantly moving. Even after they settle, often in cities, it can be hard to find them without help from their communities. Moving from camps to cities also makes it hard to keep track of their health over time and to make sure they get the care they need. Also, many refugee camps are in poor and unstable areas, which means there may not be enough tools or money for research or for proper medical care. People in these areas might also face more unfair treatment and have less access to basic needs like education and jobs, which can add to their stress.

Once researchers connect with displaced people, building trust and being careful with private information are very important. People might be scared to take part in studies because they fear it could lead to problems, losing help, or shame. They might not feel free to say "no" to joining a study, especially in camps where they have little freedom. They might also feel like they have to take part to get medical help, since there are often not enough doctors. For these reasons, research in displaced communities should be led by people from those communities who understand their language, culture, and experiences.

Researchers who are not from these communities should learn about their culture. Research teams should also include people from the community being studied. It is also helpful to use existing information and work with local groups that already help these communities. Finding ways to talk about mental health that fit the local culture is also important. This means that new studies can help create better ways to work with communities and measure mental health in a way that makes sense to them.

Why Is It Important?

Most brain science research on trauma focuses on soldiers and people in cities who are affected by poverty. However, displaced people have a mix of these experiences. They are regular people who go through war trauma, personal trauma, poverty, and stress in new cities. Their experiences are unique and different from those of soldiers or other people who have faced trauma. Since about 1% of the world's population is forced to move, it is important to study how trauma affects their brains. This helps make sure everyone is included in research and helps us understand trauma better in general. Also, fixing health differences for displaced people and other groups could save a lot of money. Good brain research on refugees could lead to more help, better ways to prevent problems, and treatments that fit their culture.

Learning about how trauma affects the brain can also help fight shame and encourage people to get help. For example, showing that trauma affects a refugee's brain just like it affects a soldier's brain can help people understand that trauma is universal. This can help the public and the people who experience trauma understand what is happening in their brains. Knowing that mental illness is a physical illness can help reduce shame and encourage people to accept medical treatments.

Finally, a main goal of brain science research is to find better ways to prevent and treat problems. When it comes to treatment, cultural differences, language barriers, and the unique traumas of displaced people mean that treatments need to be changed to fit their needs. Brain science can help by finding ways to measure changes in the body that show if treatments are working. Also, many drug studies do not include people from the cultures and backgrounds of refugees. It is important to know that genetic and body differences might mean that medicines work differently for these groups. More research is needed to understand how genes, body differences, culture, and feelings all affect how people respond to medicine.

Call to Action: How to Get There

War, natural disasters, and being forced to move have always been a part of human history. This means that displaced people have higher rates of PTSD and other mental health problems. Refugees and migrants have special experiences and different cultures, environments, and genes. They also face health differences that set them apart from the groups usually studied in brain science. It is important to understand their unique experiences to include them in research and find ways to help them at all levels. We do not have enough information in this area, which means we cannot fully understand how their brains are affected or create good ways to prevent and treat their problems. To fix this, we have some ideas.

Researchers should focus on questions specific to displaced people. Most research on migrants and refugees looks at how many people have problems and what in their environment causes it, but brain science research is missing. We can encourage more brain science research in these groups by:

1. Teaching people about these groups and why this research is important.

2. Giving money specifically for this research through grants.

3. Talking about displaced people at big meetings and in important journals. This can include inviting researchers who work with refugees to meet brain scientists.

It is also important to provide help and knowledge in places that have many refugees. For example, many Syrian and Iraqi refugees live in nearby countries in the Middle East. These countries often do not have as many brain science research tools as places like the United States. Connecting research teams worldwide can help fill these gaps and make research stronger and faster for everyone.

Brain research in places where refugees settle should use tools that are right for different cultures and have been proven to work. Researchers should be careful about cultural feelings. For example, some cultures might not feel comfortable talking about certain past experiences. Researchers should also look at stress and trauma related to being displaced and facing unfair treatment. It is good to use different types of research methods together. Studies should also involve people from the community in the research team as equal partners. The research should be about what the community needs, and the results should be shared with them. This helps make sure people join the studies and that the research is helpful.

Researchers should also think about how to do good science even when there are challenges like long distances, no internet, or no phones. Using mobile technology to collect information outside of labs can help include more people.

Lastly, because trauma and stress continue for refugees and migrants, research needs to look at these problems over time. Instead of just checking if someone has PTSD at one moment, it is important to see how their situation changes. A person might meet the criteria for PTSD at one time but not another, depending on the stress they are facing. Looking at these changes over time will help us understand what helps people stay strong and what treatments work best.

Even with all the challenges, displaced people are often very strong. Learning about their strengths can help us find better ways to treat people who are more affected by trauma and stress. While there is still a lot to do, efforts to understand the experiences of many different groups are growing and will greatly improve the field of brain science.