Table 1.

Delineating the review question and refining the search strategy based on PICo-approach

PICo search strategy	Inclusion criteria	Exclusion criteria
Population	Migrants (as defined by IOM) and Ethnic Minority groups. This includes, for example, second-generation migrants, economic migrants, people migrating because of family reunification, undocumented migrants (While these definitions include the refugees and asylum seekers, we excluded them if interventions were solely targeted at refugees and asylum seekers, see exclusion criteria)	Studies solely focused on refugees and asylum seekers. Rationale: asylum seekers and refugees have different mental health needs. When ethnicity/migrant background is included as a control variable and not the focus of the study, we do not include them in the review
	Adults aged +18 years old	Children or adolescents aged −18 years old. Rationale: children and adolescents may experience different mental health needs and specified intervention approaches
Interest	Studies describing interventions oriented at improving mental health/well-being outcomes; other interventions can be included if they provide a clear link to mental health outcomes	Studies describing interventions without (a link to) outcome measures for mental health or well-being. Studies describing purely medical/pharmacological interventions are excluded. Articles relating to broad policies are excluded from the results, but we included them where relevant in the discussion to stimulate debate
Context	All countries of EU/EEA + UK and Switzerland; if more countries are involved in the study (e.g., high-income countries), we include the paper but only focus on the European part	Studies solely focused on countries outside EU/EEA + UK. Rationale: we only include studies related to the geographical region of Europe to limit the variability in study contexts