Background. A randomized trial of a primary care-based intervention to prevent depression relapse resulted in improved adherence to long-term antidepressant medication and depression outcomes. We evaluated the effects of this intervention on behavioural processes and identified process predictors of improved depressive symptoms.

Method. Patients at high risk for depression recurrence or relapse following successful acute phase treatment (N=386) were randomly assigned to receive a low intensity 12-month intervention or continued usual care. The intervention combined education about depression, shared decision-making regarding use of maintenance pharmacotherapy and cognitive-behavioural strategies to promote self-management. Baseline, 3, 6, 9 and 12-month interviews assessed patients' self-care practices, self-efficacy for managing depression and depressive symptoms.

Results. Intervention patients had significantly greater self-efficacy for managing depression (P<0·01) and were more likely to keep track of depressive symptoms (P<0·0001), monitor early warning signs (P<0·0001), and plan for coping with high risk situations (P<0·0001) at all time points compared to usual care control patients. Self-efficacy for managing depression (P<0·0001), keeping track of depressive symptoms (P=0·05), monitoring for early warning signs (P=0·01), engaging in pleasant activities (P<0·0001) and engaging in social activities (P<0·0001) positively predicted improvements in depression symptom scores.

Conclusions. A brief intervention designed to target cognitive-behavioural factors and promote adherence to pharmacotherapy in order to prevent depression relapse was highly successful in changing several behaviours related to controlling depression. Improvements in self-efficacy and several self-management behaviours that were targets of the intervention were significantly related to improvements in depression outcome.