BMC Public Health Study protocol Effectiveness and cost-effectiveness of an exposure-based return-to-work programme for patients on sick leave due to common mental disorders: design of a cluster-randomized controlled trial Erik Noordik*1, Frank J van Dijk1, Karen Nieuwenhuijsen1 and Jac JL van der Klink2 BioMed Central Open Access Address: 1Coronel Institute of Occupational Health, Academic Medical Center (AMC), University of Amsterdam, PO Box 22700, 1100 DE, Amsterdam, The Netherlands and 2University Medical Center Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands Email: Erik Noordik* - f.w.noordik@amc.nl; Frank J van Dijk - f.j.vandijk@amc.nl; Karen Nieuwenhuijsen - k.nieuwenhuijsen@amc.nl; Jac JL van der Klink - j.j.l.van.der.klink@med.umcg.nl * Corresponding author Published: 13 May 2009 BMC Public Health 2009, 9:140 doi:10.1186/1471-2458-9-140 This article is available from: http://www.biomedcentral.com/1471-2458/9/140 Received: 15 February 2009 Accepted: 13 May 2009 © 2009 Noordik et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: To reduce the duration of sick leave and loss of productivity due to common mental disorders (CMDs), we developed a return-to-work programme to be provided by occupational physicians (OPs) based on the principles of exposure in vivo (RTW-E programme). This study evaluates this programme's effectiveness and cost-effectiveness by comparing it with care as usual (CAU). The three research questions we have are: 1) Is an RTW-E programme more effective in reducing the sick leave of employees with common mental disorders, compared with care as usual? 2) Is an RTW-E programme more effective in reducing sick leave for employees with anxiety disorders compared with employees with other common mental disorders? 3) From a societal perspective, is an RTW-E programme cost-effective compared with care as usual? Methods/design: This study was designed as a pragmatic cluster-randomized controlled trial with a one-year follow-up and randomization on the level of OPs. We aimed for 60 OPs in order to include 200 patients. Patients in the intervention group received the RTW-E programme. Patients in the control group received care as usual. Eligible patients had been on sick leave due to common mental disorders for at least two weeks and no longer than eight weeks. As primary outcome measures, we calculated the time until full return to work and the duration of sick leave. Secondary outcome measures were time until partial return to work, prevalence rate of sick leave at 3, 6, 9, and 12 months' follow-up, and scores of symptoms of distress, anxiety, depression, somatization, and fatigue; work capacity; perceived working conditions; self-efficacy for return to work; coping behaviour; avoidance behaviour; patient satisfaction; and work adaptations. As process measures, we used indices of compliance with the intervention in the intervention group and employee-supervisor communication in both groups. Economic costs were calculated from a societal perspective. The total costs consisted of the costs of consuming health care, costs of production loss due to sick leave and reduced productivity, and out-of-pocket costs of patients for travelling to their OP. Discussion: The results will be published in 2009. The strengths and weaknesses of the study protocol are discussed. Trial registration: ISRCTN72643128 Page 1 of 11 (page number not for citation purposes)