Background: Depression is a common illness with great human costs and a significant burden on the public economy. Previous studies have indicated that collaborative care (CC) has a positive effect on symptoms when provided to people with depression, but CC has not yet been applied in a Danish context. We therefore developed a model for CC (the Collabri model) to treat people with depression in general practice in Denmark. Since systematic identification of patients is an “active ingredient” in CC and some literature suggests case finding as the best alternative to standard detection, the two detection methods are examined as part of the study. The aim is to investigate if treatment according to the Collabri model has an effect on depression symptoms when provided to people with depression in general practice in Denmark, and to examine if case finding is a better method to detect depression in general practice than standard detection.

Methods/Design: The trial is a cluster-randomised, clinical superiority trial investigating the effect of treatment according to the Collabri model for CC, compared to treatment as usual for 480 participants diagnosed with depression in general practice in the Capital Region of Denmark. The primary outcome is depression symptoms (Beck’s Depression Inventory (BDI-II)) after 6 months. Secondary outcomes include depression symptoms (BDI-II) after 15 months, anxiety symptoms (Beck’s Anxiety Inventory (BAI)), level of functioning (Global Assessment of Function (GAF)) and psychological stress (Symptom Checklist-90-Revised (SCL-90-R)). In addition, case finding (with the recommended screening tool Major Depression Inventory (MDI)) and standard detection of depression is examined in a cluster-randomized controlled design. Here, the primary outcome is the positive predictive value of referral diagnosis.

Discussion: If the Collabri model is shown to be superior to treatment as usual, the study will contribute with important knowledge on how to improve treatment of depression in general practice, with major benefit to patients and society. If case finding is shown to be superior to standard detection, it will be recommended as the detection method in future treatment according to the Collabri model.

Trial registration: ClinicalTrials.gov. NCT02678845. Retrospectively registered on 7 February 2016.