Objectives Both the presence of mental health problems and the absence of an employment contract have been related to long-term sickness absence and unemployment, indicating a need for return-to-work (RTW) interventions. Our aim was to study the effectiveness of a new participatory, supportive RTW program for workers without an employment contract, sick-listed 2–14 weeks due to a common mental disorder, in comparison with usual care.

Methods A participatory approach, integrated care and direct placement in a competitive job were part of the new program. The primary outcome measure was duration until first sustainable RTW in competitive employment. Cox regression analysis was applied to study this outcome. Secondary outcome measures were average working hours, duration until any type of employment, sickness benefit duration, and perceived health and functioning.

Results In total, 186 participants were included in the study and randomly allocated to an intervention group (N=94), or control group (N= 92). A hazard ratio (HR) of 1.15 (95% CI 0.61–2.16) for duration until first sustainable RTW indicated no significant effect of allocation to the new program, compared to usual care. Furthermore, no significant differences were found in favor of the intervention group on any secondary outcome.

Conclusions Compared to usual care, the new program did not result in a significant shorter duration until first sustainable RTW. However, due to low protocol adherence, it remains unclear what the results would have been if the program had been executed according to protocol.

Key terms common mental disorder; employment contract; mental disorder; occupational healthcare; randomized controlled trial; RCT; return to work; return-to-work; RTW; sick leave; sickness absence; sickness absence; temporary employment; temporary worker; unemployment; vulnerable worker