Integrated mental health care and vocational rehabilitation intervention to improve return to work rates for people on sick leave due to common mental and functional disorders (IBBIS-II) – results from a randomized clinical trial

More than 50% of people receiving long-term sickness benefits in Denmark have a common mental illness. At the same time, a significant treatment gap exists where less than 30% receive sufficient care for their mental illness. The trial was designed as an investigator-initiated, randomized, two-group parallel superiority trial. Nine hundred participants with a common mental illness were randomly assigned into two groups: (1) IBBIS II, consisting of integrated mental health care and vocational rehabilitation, or (2) service as usual (SAU), at two sites in Denmark. The primary outcome was the difference between the two groups in time to return to work (RTW) at 12 months. There was no difference between the integrated IBBIS II intervention and SAU in time from baseline to RTW at the 12-month follow-up (Hazard ratio (HR) = 1.16 (95% CI 0.99–1.37), <i>p</i> = 0.07), but there was a tendency that the IBBIS II group had worse outcomes on several exploratory employment measures, including time to return to work at 6-month follow-up (HR = 1.36 (95% CI 1.03–1.55), <i>p</i> = 0.02), and number of weeks in work at 12-month follow-up (incidence rate ratio = 1.14 (95% CI 1.04–1.27), <i>p</i> = 0.008). The integrated employment and health intervention (IBBIS II) was not more effective than SAU in any of the included vocational outcomes and may even have been inferior to SAU on certain outcome measures. Based on these results, it is not recommended that the IBBIS II intervention is widely implemented in countries with service as usual comparable with Denmark. ClinicalTrials.gov. Registered June 16, 2020, NCT04432129. https://clinicaltrials.gov/ct2/show/NCT04432129?term = IBBIS+II.