Depression remission after six months of collaborative care management: Role of initial severity of depression in outcome

Aim: The impact of initial severity of depression on the rate of remission has not been well studied. The hypothesis for this study was that increased depression severity would have an inverse relationship on clinical remission at six months while in collaborative care management. Participants: The study cohort was 1128 primary care patients from a south-eastern Minnesota practice and was a longitudinal retrospective chart review analysis. Results: Clinical remission at six months was less likely in the severe depression group at 29.6% compared with 36.9% in the moderately severe group and 45.6% in the moderate depression group (P < 0.001). Multivariate analysis of a subgroup demonstrated that increased initial anxiety symptoms (odds ratio [OR] 0.9645, 95% confidence interval [CI] 0.9345-0.9954, P = 0.0248) and an abnormal screening for bipolar disorder (OR 0.4856, 95% CI 0.2659-0.8868, P = 0.0187) predicted not achieving remission at six months. A patient with severe depression was significantly less likely to achieve remission at six months (OR 0.6040, 95% CI 0.3803-0.9592, P = 0.0327) compared with moderate depression, but not moderately severe depression (P = 0.2324). There was no statistical difference in the adjusted means of the PHQ-9 score for those patients who were in remission at sixmonths. However, in the unremitted patients, the six-month PHQ-9 score was significantly increased by initial depression severity when controlling for all other variables. Conclusion: Multivariate analysis in our study demonstrated that patients with severe depression have a decreased OR for remission at six months compared with moderate depression. Also, there was a significant increase in the six-month PHQ-9 score for those unremitted patients in the severe vs. moderate depression groups.