Results of the search strategy
Overall, we identified 2557 citations from searches and reviews of reference lists after removal of duplicates. Of these, we assessed 240 full-texts for eligibility. Finally, we included 47 studies reported in 53 articles [24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76] (see Fig. 1). 15 additional articles were accompanying articles, but did not reveal any further information relevant for our research question and were therefore excluded [8, 9, 11, 77,78,79,80,81,82,83,84,85,86,87,88]. We obtained additional data for eleven studies after contacting authors [28, 48, 53, 60, 62, 64, 66, 67, 73,74,75]. Seven studies were published in other languages than English: Danish [55, 69], German [48, 59, 75, 76] and Italian [65]. We translated the relevant information into English. Overall, ten studies [26, 31, 40, 45, 47, 51, 58, 68, 70, 73] reported mean and standard deviation for relevant outcomes. These results are presented in Additional Material 2.
Description of included studies
Table 2 provides an overview of the included studies summarizing population characteristics, data collection methods and outcomes. Studies reported information on 24,786 refugee or asylum-seeking children and adolescents living in 14 European countries (Austria, Belgium, Croatia, Denmark, Finland, Germany, Greece, Italy, Netherlands, Norway, Slovenia, Sweden, Turkey, and United Kingdom). One large register-based study already contributed data on 15,264 children and adolescents [26]. Overall, the studies included more boys than girls. The mean age of the participants varied between 5.9 and 18.6 years (range 2–23 years). Seven studies assessed the children’s and adolescent’s mental health after 2010, 13 studies were conducted between 2000 and 2010 and eight studies were conducted earlier. The length of stay in the host country ranged from 4 months to 9 years. The countries of origin varied widely with the majority of study participants coming from Africa, Afghanistan, Iran, Iraq, and countries from former Yugoslavia. Two studies [26, 57] received a low risk of bias rating and 29 studies [24, 25, 27, 30, 33,34,35,36,37,38,39, 41, 42, 44,45,46,47,48,49,50,51, 54, 56, 61, 62, 66, 68, 75, 76] received an unclear risk of bias rating (see Table 2). Reasons for unclear risk of bias ratings were mainly because the sample was a convenience sample, the sample size was not justified and rather small, or the survey’s response rate was not reported. Sixteen studies showed high risk of bias [29, 32, 52, 55, 58,59,60, 63, 65, 67, 69,70,71,72,73,74], because of low response rates (< 30%), inconsistent results, or the lack of informed consent or ethical approval (as rated by the AXIS tool).
Table 2 Study characteristics of included studies Unexplained high heterogeneity hampered the conduct of meta-analyses for all outcomes (PTSD: I2 = 96%; depression: I2 = 94%; anxiety disorder: I2 = 96%; suicidal ideation and behaviour: I2 = 90%; emotional and behavioural problems: I2 = 87%;). See Additional Material 3 for point prevalence and confidence interval (CI) for outcomes of individual studies.
Figure 2 presents an overview of the median point prevalence and the interquartile ranges of the relevant outcomes. These results are described in more detail below.
Posttraumatic stress disorder
Twenty-seven studies reported on the prevalence of PTSD, providing data on a total of 5852 young refugees or asylum seekers [24, 25, 27, 29, 30, 33, 34, 36, 38, 39, 41, 45, 46, 49, 50, 52, 56, 60,61,62,63, 65, 67, 69, 72, 74, 76]. The interquartile range (IQR) for refugees and asylum seekers screening positive for PTSD was 19.0–52.7% and the median was 35.3%. The two largest studies rated with unclear risk of bias reported a PTSD prevalence of 42.3% (95% CI 39.1%, 45.6%, n = 875) [53] and 52.0% (95% CI 48.7%, 55.2%, n = 895) [45]. PTSD was screened via self-report questionnaires (Impact of War-related Trauma Events [IWRITE], Reactions of Adolescents to Traumatic Stress Questionnaire [RATS]).
Generally, studies relying on clinical interviews for the diagnosis of PTSD showed a lower PTSD prevalence than studies using self-report or proxy-questionnaires (IQR 19.2–36.0% vs. 25.6–62.7%). Three studies directly compared differences between unaccompanied and accompanied children and adolescents. They reported a higher prevalence for being screened positive for PTSD or to be diagnosed with PTSD among unaccompanied than accompanied children and adolescents (Study 1 [different accompanied groups]: 36.7% vs. 5.7–12.7% [33]; Study 2 [gender]: 61.5–73.1% vs 14.3–35.3% [38]; and Study 3: 50% vs. 0% [63]).
Overall, the quality of evidence regarding the prevalence of PTSD in refugee and asylum-seeking children and adolescents is low. This is because the evidence relies mainly on studies that used convenience sampling strategies (downgraded for risks of bias), and the studies’ results varied considerably (downgraded for inconsistency).
Depression
Nineteen studies, including 4150 children and adolescents, analysed the prevalence of depression [27, 29, 31,32,33, 36, 38, 39, 41, 46, 50, 52, 56, 60, 61, 65, 67, 74, 76]. The IQR for depression prevalence was 10.3–32.8% and the median was 20.7%. As for PTSD, studies using a structured clinical interview (e.g. M.I.N.I Kid) as assessment method reported lower percentages of depression 3.1% to 9.4% [39, 61, 76] compared to the median of all assessments (20.7%).
The two largest studies both using the Hopkins Symptom Checklist-37A [HSCL-37A] (a self-report questionnaire for the screening for depression) revealed very different results. In a sample of 650 accompanied refugees and asylum seekers in Belgium, the study reported a depression prevalence of 8.2% (95% CI 6.3%, 10.5%) [33]. By contrast, a study on 827 unaccompanied children and adolescents in the Netherlands [28] reported a prevalence for depression of 38.8% (95% CI 35.6%, 42.2%). The Belgian study used a higher cut-off-point (90th percentile instead of the 60th percentile), which resulted in a lower prevalence. Two studies directly comparing differences between unaccompanied and accompanied children and adolescents tended to show higher point prevalence for depression for unaccompanied children and adolescents than for accompanied children (30.2% vs. 8.2–32.8% [different accompanied groups] [33] and 11.5–23.1% vs. 5.9–52.9% [gender] [38]).
Overall, the quality of evidence regarding the prevalence of depression in refugee and asylum-seeking children and adolescents is low (downgraded for risk of bias and inconsistency).
Anxiety disorder
We identified 16 studies including 3804 children and adolescents that assessed the point prevalence of anxiety disorders [25, 27, 30, 32, 33, 36, 41, 46, 56, 58, 60, 61, 65, 67, 71, 74]. The IQR for the anxiety disorder prevalence was 8.7–31.6% and the median was 15.0%. The largest study investigating 852 unaccompanied minors in the Netherlands [28] reported a point prevalence of anxiety disorder of 46.0% (95% CI 42.7%, 49.4%). Bronstein et al. [31] applied the same questionnaire (HSCL-37A with the same cut-off point) as Bean et al. [28] in a similar war-affected unaccompanied population from Afghanistan living in the UK (n = 214), but reported a lower prevalence of anxiety disorder, 34.6% (95% CI 28.5%, 41.2%). The differences in these results could be due to differences in the host country, sampling errors or gender differences; while Bronstein et al. [31] included only boys, Bean et al. [28] included boys (70%) and girls (30%). One study directly comparing differences between unaccompanied and accompanied children and adolescents, showed higher anxiety disorder prevalence in unaccompanied children (20.2%; 95% CI 14.0%, 28.1%) than in accompanied children (8.8%; 95% CI 6.8%, 11.2%) [33].
Overall, the quality of evidence regarding the prevalence of anxiety disorder in refugee and asylum-seeking children and adolescents is low (downgraded for risk of bias and inconsistency).
Suicidal ideation and behaviour
Four studies [39, 52, 55, 76] reported on suicidal ideation and behaviour of 1184 children and adolescents revealing a median of 5.0% and an IQR of 0.7–9.3%. Unclear risk of bias studies [39, 76] relying on the assessment of 139 children and adolescents using a clinical interview (M.I.N.I. Kid) revealed higher prevalence (9.2% and 9.8%) than the two high risk of bias studies. A Danish register-based study [55] assessed suicide attempts (0.9%, 95% CI 0.4%, 1.9%) and a Slovenian study investigated “the intention to kill oneself” (0.8%, 95% CI 0.2%, 3.0%) in a sample of refugee adolescents [52].
Overall, the quality of the evidence regarding the prevalence of suicidal ideation and behaviour of refugee and asylum-seeking children and adolescents is very low (due to risk of bias, imprecision and inconsistency).
Emotional and behavioural problems
Overall, 20 studies covering 3191 refugee or asylum-seeking children and adolescents reported on emotional and behavioural problems assessed with eight different self-report or proxy-questionnaires [25, 27, 30, 32, 35, 37, 41, 42, 44, 46, 48, 50, 54, 57, 59, 61, 66, 67, 71, 75]. The IQR of the point prevalence of emotional and behavioural problems is 19.8–35.0% and the median is 25.2%. The largest study [28] reported on prevalence of emotional and behavioural problems in 41.2% (95% CI 37.9%, 44.6%) of the participating unaccompanied children and adolescents living in the Netherlands.
Other outcomes
Few studies [36, 60] reported on point prevalence of other outcomes, such as hyper activeness (1.8–6%) or psychosomatic complaints (13%) [36], any psychiatric disorders as an overall category (13.4–41.9%) [46, 61], nocturnal enuresis (10.9%) [60], and dissociative psychopathology (36%) [72]. We could not identify any studies reporting on the prevalence of bipolar disorder, eating disorder, schizophrenia, and substance abuse of illicit drugs, alcohol and tobacco.