Objective: Numerous double-blind studies have assessed the efficacy of antidepressants in treating chronic depressive disorder, including dysthymic disorder, low-grade chronic depression. However, there are no double-blind, placebo-controlled studies of serotonin-norepinephrine reuptake inhibitors in chronic depressive disorder.
Method: Outpatients with chronic depressive disorder, but without concurrent major depressive disorder (MDD), were randomly assigned to prospective double-blind duloxetine (beginning at 30 mg/d, increased to a maximum dose of 120 mg/d) versus placebo for 10 weeks. Inclusion criteria were current DSM-IV-TR diagnosis of dysthymic disorder or depression not otherwise specified, age 18-75 years, and a Hamilton Depression Rating Scale (HDRS) score ≥ 12. Exclusion criteria included current major depression. The study was conducted between August 2006 and December 2011. HDRS, Cornell Dysthymia Rating Scale (CDRS), Clinical Global Impressions (CGI), Beck Depression Inventory (BDI), Global Assessment of Functioning (GAF), Social Adjustment Scale (SAS), and other assessments were administered at each visit. We hypothesized that duloxetine would be superior to placebo in (1) 24-item HDRS total score, (2) the percentage of subjects classified as responders and remitters, and (3) secondary measures (CDRS, BDI, CGI). Response was defined as > 50% decrease in 24-item HDRS and CGI-Improvement scale score of 1 or 2 ("very much improved" or "much improved"). Remission was defined as HDRS-17 item score ≤ 4 and 0 on item 1 of the HDRS (depressed mood).
Results: 65 subjects were enrolled, of whom 57 began medication. They ranged in age from 19 to 70 years (mean ± SD = 41.63 ± 11.22) and included 24 women and 33 men. Baseline 24-item HDRS score (mean ± SD) for both groups was 20.75 ± 4.92. After 10 weeks, duloxetine-treated subjects had significantly lower 24-item HDRS scores than placebo-treated subjects (time-by-drug group effect on analysis of variance: F1,55 = 9.43, P = .003). Responder and remitter analyses significantly favored duloxetine treatment. The response rate was 65.5% for duloxetine versus 25.0% for placebo (χ(2)(1) = 9.43, P = .003); and the remitter rate was 55.2% for duloxetine versus 14.3% for placebo (χ(2)(1) = 10.46, P = .002). After 10 weeks, duloxetine-treated subjects did not differ significantly better from placebo-treated subjects on the SAS (time-by-drug group effect on analysis of variance: F(1,46) = 0.35, P = .555) or on the GAF (time-by-drug group effect on analysis of variance: F(1,51) = .01, P = .922).
Conclusions: Results on the 24-item HDRS, CGI, and CDRS suggest that duloxetine is efficacious in acute treatment of chronic nonmajor depressive disorder. Response and remission rates also differed significantly, favoring duloxetine treatment, but BDI, GAF, and social functioning (Social Adjustment Scale) did not. Duloxetine appears to be effective in acute treatment of nonmajor chronic depression.
Trial registration: ClinicalTrials.gov identifier: NCT00360724.
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