The meta-analysis presented here calculated overall prevalence of suicidal ideation and attempts in refugees and asylum seekers. Based on the eight studies included, a prevalence of 20.5% (range: 2.13% − 34.4%) was found for suicidal ideation across both genders. When distinguished by gender, a prevalence of 22.3% (n = 5) was found for women and 23.3% (n = 3) for men. Because not all studies reported prevalence for suicidal ideation stratified by sex, fewer studies could be included in the gender-differentiated analysis. In regard to the prevalence in women, it should be further mentioned that some studies were included in which only women were examined [39, 40]. In determining an overall prevalence of suicide attempts, it was possible to include four studies, yielding a prevalence of 0.57% (range: 0.14% − 7.55%).
Compared to global prevalence data [10–12], there is a higher prevalence of suicidal ideation among refugees. Making direct comparisons is difficult, however, because global prevalence data are often recorded as lifetime or 12-month prevalence rates. That said, in the studies considered here, periodic prevalence rates were reported that included the 1–4 weeks previous to when the surveys were administered (see Table 2). Only Cochran et al.  reported a lifetime prevalence of suicidal ideation among Bhutanese refugees in the United States of 3% (n = 423). This corresponds to the lower range of previously reported global prevalence rates .
In looking at prevalence rates for suicide attempts, we found numbers similar to those reported in cross-national studies . Again, comparison is difficult because the data on suicide attempts in the included studies reflects a variety of time periods ranging from one week to one year (see Table 2).
With one exception , studies on refugee populations report substantially higher prevalence rates of suicidal ideation compared to studies examining non-refugee populations or the general population. All in all, the results emphasize previous findings of increased psychological distress among refugees being associated with higher rates of suicidal ideation and suicide attempts. Amiri  determined the prevalence of suicidal ideation to be 16% (17% in women, 10% in men) and suicide attempts 6% (7% in women, 1% in men) when he included studies done with various immigrant groups and refugees without distinguishing between them (n = 29).
As mentioned above, people who leave their country of origin do so for a variety of reasons; for refugees, the flight is more often accompanied by numerous traumatic events. In addition, it must be taken into account that immigrants who have already lived and worked in their new host country for several years are exposed to different stressors than people who have been on the run for the past few months or years, and have just arrived in a host country and/or have an uncertain asylum status (pre-, peri- and post-migration factors). On the other hand, there may be an increased vulnerability as a result of pre- and peri-migration stressors, which can result in mental disorders and suicidal ideation.
Studies in immigrant populations in different European countries (e.g. Germany, Sweden) show 1st generation immigrants having less suicidal ideation than host country residents or 2nd generation immigrants (e.g. 42, 43). This phenomenon can be explained by the Protective Culture Model (e.g. 44 ). This model assumes that some protective factors against suicide might be linked with culture of origin, such as religious beliefs, stable family bonds, and social support. This reduces the stress of acculturation. However, this protection decreases with time spent in the host country, resulting in increased suicidal ideation and attempts in the second generation. In addition, the Resilient Immigrant Model (e.g. 45) also known as Healthy Migrant Effect assumes a selective effect during immigration processes, i.e., people with good health and high resilience are particularly able to cope with the challenges of migration. In the second generation, this selectivity would no longer exist. This could explain the good health of immigrants on average. Factors influencing suicidality among immigrants are acculturation stress, experiences of discrimination, cultural differences, and environmental factors, among others (for an overview, see 46). Also worth considering are post-migration stressors such as socioeconomic factors, social and interpersonal circumstances, and stressors related to the asylum process and immigration policies [16, 47], which can be burdensome. Taking into account these differences between refugees and/or asylum seekers compared to immigrants (immigrants or former refugees living in their host country for some time), it is not reasonable to equate their prevalence rates of suicidal ideation and attempts. The danger of doing so is that it could result in underestimating the general risk of suicidal ideation and suicide attempts among refugees and asylum seekers.
Strengths and limitations
The strengths of this analysis lie in the methodology that was used, which is based on current research standards [27, 32, 35, 48]. All studies were rated "moderate" or "strong" in quality assessment (Table 2). In some cases, however, the sample sizes were relatively small (e.g. 18, 25, 49, 50), which could have an impact on external validity. Another limitation is the small number (n = 11) of studies that could be integrated into the meta-analysis after reviewing articles’ full texts. For this reason, the generalizability of the results is of a rather limited nature. We included studies that were not initially designed as epidemiological studies, but in which descriptive data of the periodic prevalence of suicidal ideation and attempts among refugees and asylum seekers were recorded. Furthermore, no gray literature search was conducted, so there may be unpublished research that was not included. The generalizability of the results regarding suicidal ideation in women may be further impaired by the fact that very specific groups of women were studied, for example, female refugees in a partnership  or exclusively mothers , groups that may be affected by additional protective or risk factors not accounted for in the scope of the examinations.
In view of the different survey methods (mainly self-report) used to record suicidal ideation and suicide attempts, of the included studies, the appropriateness of calculating pooled prevalence estimates could be questioned as well as internal validity. In general, in order to compare test results in different cultural groups, equivalence in language and construct validity must be taken into account.
Because of high heterogeneity between studies, the pooled prevalence estimates should be interpreted with caution. Heterogeneity can be defined as any type of variability between studies in a systematic review or meta-analysis. Therefore possible covariates of heterogeneity can be the quality of the studies, the sample, the year of publication, and/or the research method used [51–53]. In order to be able to understand the variance across studies depending on the factors just mentioned, subgroup analyses are helpful. These, however, could not be performed in the present meta-analysis due to the small number of studies included (there must be at least 10 studies to perform a subgroup analysis, 54). Thus, future research in the same field of interest should focus in more detail on subgroups regarding differences in host countries, cultural characteristics such as religion or attitudes toward mental disorders, country of origin, and flight duration and/or route, etc.