Table 3 Methodological characteristics of the included studies (n = 13)

Study design

 Feasibility/pilot study

5 [38, 39, 42, 45, 47]

 Randomized controlled trial

4 [39, 44, 46, 48]

 Quasi-experimental trial

2 [37, 43]

 Qualitative evaluation

2 [41, 49]

 Controlled trial

1 [40]

Participant recruitment

 Convenience sampling

8 [38,39,40, 42, 43, 45,46,47]

 Unclear recruitment strategy

3^a [37, 41, 49]

 Snowball sampling

2 [45, 46]

 Random component in the recruitment strategy

2 [44, 48]

 Register-based recruitment

1 [44]

Allocation of intervention and control groups

 Cluster-randomized allocation

4 [42, 44, 45, 48]

 Randomized allocation

4 [37, 39, 43, 46]

 Convenience allocation

1 [46]

 Non-randomized allocation depending on symptoms

1 [47]

 Quasi-randomized allocation

1 [40]

Controls

 Active control group or enhanced usual care

5 [40, 42, 44, 45, 48]

 Control group with treatment as usual or waitlist

5 [37, 39, 43, 45, 46]

 No control group

3 [38, 41, 49]

Region where intervention was evaluated

 North America

4 [38, 43, 45, 49]

 Asia

3 [42, 44, 46]

 Middle East

3 [37, 39, 41]

 Africa

1 [48]

 Europe

1 [40]

 South America

1 [47]

Region of origin among participants

 Asia

5 [42,43,44, 46, 49]

 Africa

3 [38, 45, 48]

 Middle East

3 [37, 39, 41]

 Europe

1 [40]

 South America

1 [47]

Migration status of participants

 Refugees

9 [37,38,39, 41, 43, 45, 46, 48, 49]

 Internally displaced persons

2 [42, 47]

 Unclear status

2 [40, 44]

 Asylum seekers

1 [46]