Clinical effectiveness of collaborative care for depression in UK primary care (CADET): cluster randomised controlled trial

Objective To compare the clinical effectiveness of collaborative care with usual care in the management of patients with moderate to severe depression. Design Cluster randomised controlled trial. Setting 51 primary care practices in three primary care districts in the United Kingdom. Participants 581 adults aged 18 years and older who met ICD-10 (international classification of diseases, 10th revision) criteria for a depressive episode on the revised Clinical Interview Schedule. We excluded acutely suicidal patients and those with psychosis, or with type I or type II bipolar disorder; patients whose low mood was associated with bereavement or whose primary presenting problem was alcohol or drug abuse; and patients receiving psychological treatment for their depression by specialist mental health services. We identified potentially eligible participants by searching computerised case records in general practices for patients with depression. Interventions Collaborative care, including depression education, drug management, behavioural activation, relapse prevention, and primary care liaison, was delivered by care managers. Collaborative care involved six to 12 contacts with participants over 14 weeks, supervised by mental health specialists. Usual care was family doctors’ standard clinical practice. Main outcome measures Depression symptoms (patient health questionnaire 9; PHQ-9), anxiety (generalised anxiety disorder 7; GAD-7), and quality of life (short form 36 questionnaire; SF-36) at four and 12 months; satisfaction with service quality (client satisfaction questionnaire; CSQ-8) at four months. Results 276 participants were allocated to collaborative care and 305 allocated to usual care. At four months, mean depression score was 11.1 (standard deviation 7.3) for the collaborative care group and 12.7 (6.8) for the usual care group. After adjustment for baseline depression, mean depression score was 1.33 PHQ-9 points lower (95% confidence interval 0.35 to 2.31, P=0.009) in participants receiving collaborative care than in those receiving usual care at four months, and 1.36 points lower (0.07 to 2.64, P=0.04) at 12 months. Quality of mental health but not physical health was significantly better for collaborative care than for usual care at four months, but not 12 months. Anxiety did not differ between groups. Participants receiving collaborative care were significantly more satisfied with treatment than those receiving usual care. The number needed to treat for one patient to drop below the accepted diagnostic threshold for depression on the PHQ-9 was 8.4 immediately after treatment, and 6.5 at 12 months. Conclusions Collaborative care has persistent positive effects up to 12 months after initiation of the intervention and is preferred by patients over usual care. Trial registration number ISRCTN32829227.