ABSTRACT
Apathy in the context of treated major depressive disorder (MDD) is a common but understudied symptom. This multicenter, double-blind, randomized study investigated whether switching from a selective serotonin reuptake inhibitor (SSRI) to a serotonin-norepinephrine reuptake inhibitor (SNRI), compared with switching to another SSRI, improved apathy symptoms in patients who had been treated with a SSRI for MDD for ≥ 3 months, were no longer depressed (Montgomery-Åsberg Depression Rating Scale [MADRS] total score ≤ 15), and continued to have apathy (Apathy Evaluation Scale--Clinician rated version [AES-C] total score >30). Following 8 weeks of treatment, both the duloxetine (SNRI, 244 patients) and escitalopram (SSRI, 239 patients) groups significantly improved from baseline on the AES-C total score (least squares mean change [standard error]: duloxetine -13.9 [0.54]; escitalopram -13.5 [0.54], both P < 0.001), and on the secondary apathy, depression, and functional outcomes. There were no significant differences between the two groups on any measure, including AES-C total score (least squares mean difference [95% confidence interval]: -0.4 [-1.87 to 1.10], P = 0.612; primary objective). There was a significant within-group improvement in apathy in the subgroup who received escitalopram before and during the study. There were few differences in safety between the two groups. This study did not support the hypothesis that switching from a SSRI to a SNRI has a beneficial effect on apathy symptoms. However, given the study limitations, it is possible that more specific targeting of the noradrenergic pathway would be of benefit.