Intensified return to work clinical aftercare for sick-listed employees with diagnosed mental disorders in Germany: effects of a multicentre randomized controlled trial

Abstract Background Mental disorders are a leading cause of sickness absence and disability in Europe. They often follow chronic or recurrent patterns, hindering a sustainable return to work (RTW). In Germany, RTW aftercare interventions focusing on maintaining recovery and minimizing relapse among employees transitioning from psychiatric treatment to the workplace are scarce. We therefore developed an intensified RTW clinical aftercare program (RTW-PIA). This study aimed to ( i ) evaluate the effectiveness of RTW-PIA in addition to Care as Usual (CAU) on achieving sustainable RTW (SRTW) compared to CAU only, ( ii ) assess its impact on secondary outcomes, and ( iii ) explore potential moderators. Methods This multicentre randomized controlled trial, conducted in psychiatric outpatient clinics, included sick-listed employees diagnosed with a mental disorder. Participants ( N = 484) were randomized to RTW-PIA + CAU ( n = 240) or CAU only ( n = 244). RTW-PIA is an 18-month multimodal aftercare combining medical-psychotherapeutic and work-oriented components. Primary outcome was self-reported SRTW, defined as ≤ 6 weeks of sickness absence within 12 months after full RTW. Primary and secondary outcomes (e.g., RTW self-efficacy, work ability) were collected at baseline and at 6, 12, 18, and 24 months. Intention-to-treat analyses used logistic regression and growth curve models, complemented by prespecified sensitivity and exploratory moderator analyses. Results Overall, RTW-PIA had no significant effect on achieving SRTW (OR = 1.38 [95% CI 0.89 to 2.12]). Secondary outcomes revealed no significant effects, despite a consistent pattern of slight improvements favoring RTW-PIA. Per-protocol and complete-case sensitivity analyses led to the same conclusion. In diagnostic subgroup sensitivity analyses, employees with recurrent depressive disorders showed significant improvements in several secondary outcomes. Prespecified exploratory moderator analyses suggested potential benefits for employees without a recognized disability degree and for those with low social support at work. After multiplicity adjustment, only recurrent depressive disorder still moderated the treatment effect on work ability. Conclusions On average, RTW-PIA did not significantly improve SRTW or secondary outcomes. Employees without a recognized disability degree, with low social support at work, or with diagnosed recurrent depressive disorders might benefit from RTW-PIA. These hypotheses need to be tested in independent samples. Further research should also focus on the implementation of RTW-PIA. Trial registration DRKS00026232 (prospectively registered on 01/09/2021).