Effectiveness of a scalable, remotely delivered stepped-care intervention for psychological distress among Polish migrant workers in the Netherlands: The RESPOND randomised controlled trial

Background: Many international migrant workers (IMWs) in the Netherlands experience symptoms of anxiety and depression, often linked to adverse work and living conditions, yet underutilise mental healthcare. Stepped-care approaches may improve access by offering low-intensity support, followed by more intensive treatment if needed. We evaluated the effectiveness of a culturally adapted, remotely delivered, scalable stepped-care intervention combining guided online self-help (Doing What Matters in Times of Stress; DWM; step 1) and individual psychological support via videoconferencing (Problem Management Plus; PM+; step 2) both delivered by non-professional helpers, among Polish migrant workers living in the Netherlands. Methods and findings: In this parallel-group, two-arm, superiority randomised controlled trial, conducted in the Netherlands, Polish-speaking migrant workers aged 18 years or older with elevated psychological distress (Kessler Psychological Distress Scale; K10 ≥ 16) were recruited between May 2022 and January 2024 via social media and Polish community spaces. All participants received Psychological First Aid (PFA) before being informed about their allocation. Participants were randomly assigned 1:1 to care-as-usual or stepped-care (DWM, followed by PM+ if distress persisted; K10 ≥ 16) using computer-generated randomisation with permuted blocks in Castor Electronic Data Capture (Castor EDC). Participants and the main researcher were not blinded after allocation; outcomes were self-reported, and research assistants handling later incidental follow-up contact remained blinded. Assessments occurred at four timepoints: baseline (week 1), post-DWM (week 7), post-PM+ (week 13), and 2-month follow-up (week 21). The primary outcome was a composite measure of anxiety and depression (Patient Health Questionnaire-Anxiety and Depression Scale; PHQ-ADS), measured at all timepoints, with the primary endpoint at follow-up. Primary analyses followed the intention-to-treat (ITT) principle using linear mixed models adjusted for baseline PHQ-ADS values. In total, 218 participants were randomised and included in the ITT analysis (109 in each group); PHQ-ADS data at the primary endpoint were available for 94 participants in the intervention group and 101 in the control group. At follow-up, adjusted mean PHQ-ADS scores were lower in the intervention group than in the control group (14.8 versus 21.3), with a between-group mean difference adjusted for baseline PHQ-ADS score of −6.52 (95% confidence interval [CI] [−8.73, −4.31]; p