Exposure to war, armed conflicts, and persecution in many parts of the world have led to the flight of as many people as never before. The number of forcibly displaced people worldwide reached up to 103 million in mid-2022 (1). By the end of 2021, 36.5 million refugees, nearly half of the refugee population then, were children and adolescents under the age of 18 years (1). Refugee children and adolescents are likely to experience a variety of potentially traumatizing events in their home country, during the flight, and also in their host country (2, 3). These potentially traumatic experiences can lead to severe mental health problems (2). Besides post-traumatic stress disorder (PTSD), one of the most common mental disorders in refugee children and adolescents is depression. A recent systematic review and meta-analysis found an overall prevalence of 13.8% of depression in refugee minors (4). Another systematic review reported a prevalence rate of depression between 10.3% and 32.8% in refugee children, which is considerably larger than the prevalence rate of depression in the general population of children and adolescents (3). Refugee minors with mental health problems often met the criteria for more than one mental health disorder (5), but there is little research about the comorbidity of depression and PTSD in refugee children and adolescents. Nevertheless, Im and colleagues (6) found high rates of comorbidity among Somali refugees in Kenya, with estimates ranging from 21.6% to 28.8%. A recently conducted study examining trauma and levels of psychological distress among unaccompanied refugee minors found estimates ranging between 53.3% and 65.2% for a probable comorbidity of PTSD and depression diagnosis (7). In a small sample of Yazidi refugee minors, PTSD and depression were comorbid in 7.3% of the refugee children andadolescents (8). While several symptoms overlap between a PTSD and depression diagnosis, previous research indicated that both disorders constitute two distinct concepts (9–12). A high comorbidity for PTSD and depression remained even when disregarding overlapping symptoms, and the PTSD or depression symptoms were more strongly associated to symptoms included in the same diagnosis compared to symptoms included in the respective other diagnosis (11, 13). Still the comorbidity between both disorders might be due to relations between individual symptoms, i.e., the presence of specific PSTD symptoms might lead to the presence of depression symptoms or vice versa (13). Overlapping symptoms such as sleep problems as well as non-overlapping symptoms such as avoidance of thought seem to play a role for connecting depression and PTSD symptoms (13–15). Initial research indicated that PTSD might be a causal factor for developing subsequent depression; however, their relationship is likely to be complex and bi-directional (12, 16).

To better understand the mental health problems of refugee minors, factors influencing their mental health problems have been investigated. The association of gender with depression in refugee minors seems to be rather heterogeneous in previous literature (17, 18). Fazel and colleagues (18) reported in their review that approximately half of the studies found that girls had more depressive symptoms than boys, while other studies did not find such a gender-related difference. The systematic review of Daniel-Calveras and colleagues (17) also displayed such contradicting results. Furthermore, there seem to be an association between the age at migration and mental disorders (17). A higher age seems to be correlated with a higher burden of psychological problems (19) and with less changing symptoms of depression over time (20). Next to demographic variables, factors of the minors’ circumstances can also influence the likelihood of developing mental health problems. Most studies show that a larger number of traumatic experiences are related to more mental health problems (17). As a longer duration of flight might be associated with more traumatic events, flight duration might also impact mental health problems. However, so far, this was not explicitly studied. Furthermore, unaccompanied minors were more likely to experience higher levels of depression (21) and PTSD (22) compared to accompanied children and adolescents. Another factor possibly influencing the mental health of the refugee children and adolescents is the security of their residence status in the host country. In Germany, refugee minors receive a rather safe residence status (e.g., permission to stay in Germany for 3 years) if they obtain asylum or require refugee protection (23). In short, refugees receive asylum or refugee protection if they can prove that they are persecuted in their home country (24). Subsidiary protection for an initial period of 1 year is granted when the refugee can provide compelling reasons why they face serious harm from political or non-political actors in their home country (25). Current literature suggests that the residence status of refugee children and adolescents is associated with a PTSD diagnosis (26). A systematic review reported that refugee minors with only temporary residency had higher mental health problems compared to those with permanent residency (27). Strikingly, most previous evidence on risk factors in refugee minors relate to mental health problems in general or to PTSD, but hardly directly to depression.

Taken together, refugee minors show a higher prevalence of depression than minors in the general populations, and several factors seem to influence the likelihood of mental health problems in refugee minors. However, as pointed out by Kien and colleagues, the evidence for the prevalence of depression is limited for refugee minors due to risk of bias and inconsistency in previous studies (3). Furthermore, the majority of the current studies on risk factors for mental disorders in forcibly displaced children and adolescents refer primarily to PTSD as an outcome and depression more incidentally (17). Thus, no clear picture on the prevalence and risk factors for depression in refugee minors has emerged yet. One issue that further hampers the understanding of risk factors for depression is that the effect of each individual factor has been investigated in isolation to other factors. This ignores that risk factors also influence each other and together impact the development of depression—for example, unaccompanied children seem to experience significantly more traumatic events than accompanied refugee minors (17) and a longer flight duration is also probably related to a higher number of traumatic events. In this, the interplay between risk factors can be seen as a complex system of interacting variables, and it needs to be investigated as such.

Therefore, the aims of this cross-sectional study were threefold: (1) reporting the prevalence of depression and its comorbidity with PTSD in young forcibly displaced patients of an outpatient healthcare center for refugees in Hamburg, Germany, (2) investigating a variety of associated factors as predictors for a diagnosis of depression in these refugee minors, and (3) exploring the associations among all assessed factors and depression as a complex interacting system with a network analysis.

As refugee minors are likely to experience a variety of mental health problems but most knowledge on mental health in refugee minors relate to PTSD, we aimed to assess the prevalence and associated factors for depression in refugee children and adolescents. Furthermore, we assessed how individual factors interact with each other to gain insight into how these factors might directly or indirectly lead to depression. We found that nearly half of this clinical sample met the diagnostic criteria for depression and about half met the criteria for a PTSD diagnosis. Furthermore, about one-third of the young patients experienced comorbid depression and PTSD. Our analysis found strong evidence that older age, female gender, a higher number of traumatic experiences, and a PTSD diagnosis increased the likelihood of meeting the criteria for a moderate or severe depressive episode. With the help of network analysis, we could show that depression was only directly related to age, gender, and PTSD and that flight-related factors were mainly associated to each other and with a PTSD diagnosis.

The observed prevalence of depression is substantially higher than in previous investigations (3, 4), which is not surprising given the clinical nature of this sample (our analyses included children and adolescents that approached the outpatient clinic because of psychological distress). Still, it emphasizes that refugee minors are at a high risk of developing depression and that there is a considerable need for appropriate treatment. The current study also strikingly showed that depression and PTSD are highly comorbid in refugee youth, as the majority of the sample either had both a depression and PTSD diagnosis or no depression and no PTSD diagnosis. This finding aligns with previous research indicating that depression and anxiety disorders are highly comorbid (37). The finding that older age and female gender are related to depression diagnosis aligns well with research on non-refugee children (38). Similarly, our study could confirm previous literature on the importance of the number of traumatic experiences for experiencing mental health problems (17). With more interpersonal traumatic events experienced, the refugee children were more likely to experience a depressive episode. The strongest predictor of a depression diagnosis was a PTSD diagnosis. This indicates that the activation of PTSD symptoms might have also led to the activation of depression symptoms. Previous studies already showed that depression and PTSD symptoms were strongly linked (14, 15). These findings suggest that PTSD symptoms might lead to the activation of depressive symptoms. Therefore, it might be advisable to also monitor depression symptoms in refugee youth that experience PTSD. However, the pathways between PTSD and depression are likely to be complex and may vary between patient groups (11, 37). Thus, more research on the relation between depression and PTSD is needed.

The network analysis could shed some light on how the different associated factors interacted with each other and directly or indirectly impacted the likelihood of experiencing depression. Interestingly, all environmental factors that related to the fact that children and adolescents fled their home country were only indirectly related to depression. While duration of flight, number of traumatic experiences, accompanying status during flight and residence status were related to each other, we found only evidence for the association between number of traumatic experiences and PTSD, which, in turn, was highly related to depression—that is all environmental risk factors were only connected with depression via the number of traumatic events and PTSD. This indicates that in refugee youth flight-related factors seem to influence the likelihood of a PTSD diagnosis which then was associated to depression. Some risk factors might act indirectly through other risk factors on the likelihood of developing depression—for example, female gender, being unaccompanied, and a longer duration of flight were associated with a higher number of traumatic events. This emphasized that risk factors form a complex system of interacting variables, and to promote our understanding of these, we need to investigate their associations simultaneously.

The current study is limited by the fact that we could only investigate cross-sectional associations; therefore, the results can only offer a hypothesis on causal relations between the investigated variables. Furthermore, as all included children and adolescents were recruited at one outpatient center in Germany, future research needs to investigate if such results generalize to other refugee minor samples. Additionally, this study assessed a clinical sample of refugee minors that sought treatment in an outpatient clinic. Thus, the current sample is not representative of the general population of refugee minors in Germany. Finally, the logistic regression indicated that only 21% of the variance in depression were explained by the included variables. Thus, other variables might also play an important role for depression in refugee youth—for example, daily stressors such as worries about family members back in their home countries, perceived discrimination, economic concerns, and others. Still by investigating a large sample and using robust Bayesian analyses, we could gain insights into a highly relevant topic: the mental health of refugee children and adolescents. If future studies replicate our findings, this will indicate that refugee minors with a PTSD diagnosis should be also monitored for depressive symptoms. The next step would be to provide a suitable treatment in order to stop the PTSD symptoms from expanding to depressive symptoms. As our results showed that certain associated factors seem to influence the mental health of refugee minors indirectly, various risk factors and their associations should be considered, as these also might have indirect associations with mental health problems. Most importantly, it seems that a considerable number of refugee minors suffer from depression, and this should not be forgotten when researching and treating the mental health of refugee minors.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by Psychotherapeutenkammer Hamburg. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation in this study was provided by the participants’ legal guardians/next of kin.

LS: Conceptualization, Formal analysis, Methodology, Project administration, Writing – original draft, Writing – review & editing. JE: Data curation, Formal analysis, Methodology, Writing – original draft, Writing – review & editing. AZ: Conceptualization, Funding acquisition, Resources, Writing – review & editing. DB: Conceptualization, Data curation, Funding acquisition, Methodology, Project administration, Supervision, Writing – review & editing.