Efficacy of Antidepressants for Dysthymia: A Meta-Analysis of Placebo-Controlled Randomized Trials

Objective: The authors sought to determine the efficacy of antidepressants in dysthymic disorder and to compare antidepressant and placebo response rates between major depressive disorder (MDD) and dysthymic disorder. Data Sources: PubMed/MEDLINE databases were searched for double-blind, randomized, placebo-controlled trials of antidepressants used as monotherapy for treatment of MDD or dysthymic disorder. We defined antidepressants as those with a letter of approval by the US, Canadian, or European Union drug regulatory agencies for treatment of MDD or dysthymic disorder, which included the following: amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, trimipramine, protriptyline, dothiepin, doxepin, lofepramine, amoxapine, maprotiline, amineptine, nomifensine, bupropion, phenelzine, tranylcypromine, isocarboxazid, moclobemide, brofaromine, fluoxetine, sertraline, paroxetine, citalopram, escitalopram, fluvoxamine, zimelidine, tianeptine, ritanserin, trazodone, nefazodone, agomelatine, venlafaxine, desvenlafaxine, duloxetine, milnacipran, reboxetine, mirtazapine, and mianserin. Eligible studies were identified by cross-referencing the search term placebo with each of the above-mentioned agents. The search was limited to articles published between January 1, 1980, and November 20, 2009 (inclusive). To expand our database, we also reviewed the reference lists of the identified studies. Study Selection: We selected randomized, double-blind, placebo-controlled trials of antidepressants for either MDD or dysthymic disorder according to preset criteria relating to comorbidities, patient age, drug formulation, study duration, diagnostic criteria, choice of assessment scales, and whether or not the study reported original data. Final selection of articles was determined by consensus among the authors. Results: A total of 194 studies were found that were eligible for inclusion in our analysis. Of these, 177 focused on the treatment of MDD and 17 on the treatment of dysthymic disorder. We found that antidepressant therapy was significantly more effective than placebo in dysthymic disorder (risk ratio = 1.75; 95% CI, 1.49-2.04; P<.0001), while placebo response rates in dysthymic disorder trials were significantly lower compared to MDD trials (29.9% vs 37.9%, respectively; P=.042). Meta-regression suggested a statistically significant difference in the risk ratio of responding to antidepressants versus placebo when comparing studies either on dysthymic disorder or on MDD, suggesting a greater risk ratio for response in favor of antidepressant therapy versus placebo in patients with dysthymic disorder versus MDD (coefficient of -0.113; P=.007). Conclusions: These results support the utility of antidepressants for dysthymic disorder. In fact, the margin of efficacy of antidepressants for dysthymic disorder was larger than for MDD. Future studies providing longer-term data on the treatment of dysthymic disorder with antidepressants are essential. J Clin Psychiatry 2011;72(4):509-514 (C) Copyright 2011 Physicians Postgraduate Press, Inc.