Background: Although mania and hypomania define bipolar disorder, depressive episodes are more common and impairing, with few proven treatments. Adjunctive therapy with second-generation antidepressants is widely used to treat acute bipolar depression, but their efficacy and safety remain controversial.
Methods: In this systematic review and meta-analysis, we searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from inception to Jan 31, 2016, for randomised, double-blind, placebo-controlled trials of second-generation antidepressants adjunctive to a mood stabiliser or an antipsychotic in patients with acute bipolar depression. We extracted data from published reports. The primary outcome was change in clinician-rated depressive symptom score; secondary outcomes were clinical response, clinical remission, treatment-emergent mania or hypomania, and tolerability (using dropout rates as a proxy). We used pooled random-effects models, subgroup comparisons, and meta-regression for analyses. We made subgroup comparisons on the basis of mood stabiliser or antipsychotic treatment and did meta-regression examining trial duration. This study is registered with PROSPERO, number CRD#42015016024.
Findings: We identified six trials representing 1383 patients with bipolar depression. Second-generation antidepressants were associated with a small but significant improvement in clinician-rated depressive symptom score (standardised mean differences 0·165 [95% CI 0·051-0·278], p=0·004). However, clinical response and remission rates did not differ significantly between patients receiving adjunctive antidepressants and those receiving placebo (1·158 [0·840-1·597], p=0·371 for clinical response; 1·220 [0·874-1·703], p=0·243 for remission). Acute treatment was not associated with an increased risk of treatment-emergent mania or hypomania (0·926 [0·576-1·491], p=0·753), but 52 week extension periods were associated with an increase in risk (1·774 [1·018-3·091], p=0·043).
Interpretation: Adjunctive second-generation antidepressants are associated with reduced symptoms of acute bipolar depression, but the magnitude of benefit is small because they do not increase clinical response or remission rates. However, these medications should be used only in the short term because prolonged use is associated with an increased risk of treatment-emergent mania or hypomania.
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