Outcome measures

The primary outcome was self-rated depression severity at post-intervention assessed by the PHQ-9. The self-rating instrument assesses depressive symptoms on a 4-point Likert scale resulting in sum scores between 0 and 27 [15]. The scale provides a test–retest reliability of 0.84 and an internal consistency of α = 0.86–0.89 [15]. Validated across different populations and cultural settings [22], the PHQ-9 is recommended by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) to be used as a general measure of depression severity.

In brief, secondary outcome measures were as follows: the MÅDRS, assessing clinician-rated depression severity [16], the RHS-15 as a screening instrument for depressive symptoms, anxiety, and trauma-related disorders in refugees and asylum seekers [17], the BRS assessing the ability to recover from stress and adversity [18], the General Self-Efficacy Scale assessing patients’ sense of effective personal action control [19], the Strengths and Difficulties Questionnaire assessing emotional and behavioral problems [20], and the WHOQoL-BREF assessing patient’s quality of life [21]. Further descriptions and characteristics of these measures are reported in the Supplementary Material.