Purpose To explore why and how collaborative challenges emerge in vocational rehabilitation for citizens on long-term sick leave due to common mental disorders (CMDs), and how these challenges are experienced and navigated by key actors in the Danish sick leave system: citizens, caseworkers (CWs), and general practitioners (GPs).

Methods We conducted a case study in two Danish municipalities, including semi-structured interviews with seven citizens and seven GPs and six focus group interviews with 31 CWs. The data were analysed using systematic text condensation and abductive analysis with relational coordination theory.

Results A lack of shared goals among citizens, CWs, and GPs led to campaigning for one’s views, reinforcing competing agendas. Limited shared knowledge resulted in clarifying communication that made collaboration feel “colossally labouring.” Lack of mutual trust and respect triggered distancing communication, deepening relational divides.

Conclusion Lack of relational coordination, marked by weak relational ties and counterproductive communication, explains how collaborative challenges emerge and persist in vocational rehabilitation for people on long-term sick leave due to CMDs. The self-perpetuating nature of these dynamics highlights the need for external intervention and rethinking how organisational structures can promote relational coordination. Future research should explore contextual factors for relational coordination and potential interventions.

The authors have declared no competing interest.

This work was supported by the Centre for General Practice at the University of Copenhagen, the Department of Social Medicine at Frederiksberg Hospital, the Novo Nordisk Foundation (grant no. NNF23OC0083729), Tvaerspuljen (project no. P-2023-1-18), and Yngre Laegers Studiefond at Bispebjerg and Frederiksberg Hospital.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Regional Committee on Health Research Ethics in Denmark for the Capital Region waived ethical approval for this work (case number F-22051534).

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