A total of three multicentre RCTs (3,930 participants; 1,173 receiving usual care, 2,757 receiving collaborative care interventions) were included in the review. All three trials were considered to be of high quality, with loss to follow-up ranging from 5.9 to 31.4%. Fail-safe N values for most outcomes exceeded 20, suggesting publication bias was reasonably unlikely.
Pooled analysis of two RCTs indicated that collaborative care interventions were superior to usual care in terms of improving depression scores at three to four months (SMD -0.38, 95% CI -0.49 to -0.27), but not at 12 months. Response (OR 2.30, 95% CI 1.03 to 5.15) and remission (OR 2.57, 95% CI 1.61 to 3.33) were greater for collaborative care interventions at all follow-up periods up to 12 months.
Pooled analysis of two RCTs indicated a statistically significant decrease in suicidal thoughts from baseline for collaborative care intervention (OR 0.52, 95% CI 0.35 to 0.77) but not for usual care.
Patients receiving collaborative care interventions were more likely to report use of antidepressant medication than those receiving usual care (e.g. at 12 months OR 1.97, 95% CI 1.61 to 2.33). There was no significant difference in responders to collaborative care intervention or usual care between patients with few or many (more than two) comorbidities.
No significant differences were observed between collaborative care intervention plus provider communication and collaborative care interventions alone.