Objective: Differential predictors of response to alternative treatment options are needed to improve the outcomes in major depressive disorder. The symptom dimension comprising loss of interest and reduced activity has been reported as a predictor of poor outcome of treatment with antidepressants. We hypothesized that augmentation with partial dopamine agonist aripiprazole will be effective for individuals with pronounced interest-activity symptoms.
Methods: We tested the hypothesis in the 2-phase Canadian Biomarker Integration Network in Depression trial 1 (CAN-BIND-1). All participants had a primary diagnosis of major depressive disorder confirmed with the Mini-International Neuropsychiatric Interview. In phase 1, 188 individuals received escitalopram monotherapy 10-20 mg daily for 8 weeks. In phase 2, nonresponders received augmentation with aripiprazole 2-10 mg daily while responders continued escitalopram monotherapy for another 8 weeks. Outcomes were measured with the Montgomery-Åsberg Depression Rating Scale (MADRS) every 2 weeks. Effects of baseline interest-activity symptoms on outcomes were tested in repeated-measures mixed-effects models.
Results: Higher baseline interest-activity score (indicative of more severe loss of interest and reduction in activity) predicted worse outcome of escitalopram monotherapy in phase 1 (b = 1.75; 95% CI, 0.45 to 3.05; P = .009), but the association disappeared with the augmentation option in phase 2 (b = -0.19; 95% CI, -1.30 to 0.92; P = .739). A significant interaction between the baseline interest-activity score and aripiprazole reflected the opposite direction of the relationship between baseline interest-activity score and degree of improvement with escitalopram monotherapy versus aripiprazole augmentation (b = -1.60; 95% CI, -2.35 to -0.84; P < .001).
Conclusions: Individuals with prominent loss of interest and reduction in activity benefit less from escitalopram monotherapy and more from aripiprazole augmentation. Future trials may test the benefits of early prodopaminergic augmentation guided by interest-activity symptoms.
Trial registration: ClinicalTrials.gov identifier: NCT01655706.
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