Objective: Minor depressive disorder is both common and associated with significant psychosocial impairment. This study examined antidepressant treatment efficacy in a large group of patients with minor depressive disorder.
Method: One hundred sixty-two patients with minor depressive disorder were randomly assigned to receive fluoxetine or placebo in a 12-week, double-blind study; 73% (59 of 81) of the patients in each treatment group completed the study. Patients were evaluated weekly with standard depression rating instruments and measures of psychosocial impairment. Hypotheses were tested by last-observation-carried-forward analysis of variance (ANOVA) and confirmed by mixed (random-effects) regression analysis.
Results: At baseline, minor depressive disorder patients were mildly to moderately depressed, with a corresponding degree of functional impairment. Over 12 weeks of treatment, both ANOVA and mixed regression showed fluoxetine to be superior to placebo as indicated by significantly greater improvement of fluoxetine-treated patients in scores on the 30-item clinician-rated Inventory of Depressive Symptomatology, the 17-item and 21-item Hamilton Depression Rating Scale, the Beck Depression Inventory, and the Clinical Global Impression severity scale. Improvement in Global Assessment of Functioning Scale score was significantly greater for the fluoxetine group in mixed regression analysis only. Patients in both treatment groups reported a similar number and severity of adverse events during the 12-week treatment period.
Conclusions: Clinicians frequently encounter minor depressive disorder either as a prodromal or residual phase of illness in major depressive disorder or as de novo minor depressive disorder episodes. Fluoxetine is significantly superior to placebo in reducing minor depressive disorder symptoms within a 12-week period. Improvement in psychosocial function with fluoxetine may take longer than 12 weeks.