A workplace intervention to strengthen supervisor support for employees with common mental health problems: A mixed-methods realist evaluation

The purpose of this study is to obtain insight into whether, how and under which circumstances a novel workplace intervention works. This intervention aims to strengthen the supportive behaviour of Dutch supervisors in promoting the work participation of employees with common mental health problems (CMHPs), provided by occupational health professionals (OHPs). In a mixed-methods realist design, we evaluated changes over time, reasoning that supportive behaviour would be changed through motivation and skills and we explored how mechanisms of change may be triggered by personal, environmental and intervention factors. Compared to baseline (n = 92), self-reported supportive behaviour of supervisors increased post-intervention (n = 65, 3 months) and increased significantly post-follow-up (n = 56, 6 months). A statistically significant regression model (R2 = 0.29) indicated that factors such as increased self-efficacy and skills, being assessed as supervisor on sick leave numbers, previous collaboration between OH