Clinical factors associated with relapse in depression in a sample of UK primary care patients who have been on long-term antidepressant treatment.

BACKGROUND: This paper investigates whether age of onset of depression, duration of the last episode, number of episodes, and residual symptoms of depression and anxiety are associated with depression relapse in primary care patients who have been on long-term maintenance antidepressant treatment and no longer meet ICD10 criteria for depression. METHODS: An observational cohort using data from ANTLER (N = 478), a double-blind placebo-controlled trial. The primary outcome was time to relapse using the retrospective CIS-R. Participants were followed for 12 months. RESULTS: Primary outcome was available for 468 participants. Time to relapse in those with more than five previous episodes of depression was shorter, hazard ratio (HR) 1.84 (95% confidence interval [CI] 1.23-2.75) compared to people with two episodes; HR 1.57 (95% CI 1.01-2.43) after adjustment. The residual symptoms of depression at baseline were also associated with increased relapse: HR 1.05 (95% CI 1.01-1.09) and HR 1.06 (95% CI 1.01-1.12) in the adjusted model. There was evidence of reduced rate of relapse in older age of onset group: HR 0.86 (95% CI 0.78-0.95); HR attenuated after adjustment HR 0.91 (95% CI 0.81-1.02). There was no evidence of an association between duration of the current episode and residual anxiety symptoms with relapse. CONCLUSIONS: The number of previous episodes and residual symptoms of depression were associated with increased likelihood of relapse. These factors could inform joint decision making when patients are considering tapering off maintenance antidepressant treatment or considering other treatments to prevent relapse.