Objective: To address whether switch of depression into hypomania or mania or cycle acceleration in patients with bipolar disorder is caused by antidepressants or whether this phenomenon is attributable to the natural history of bipolar disorder itself.
Method: A critical review of the literature, pointing at sources of bias that have been previously overlooked. For examining the causation in question, the Bradford-Hill criteria were applied, i.e. specificity of the potential causative agent, strength of effect, consistency in findings, dose-response relation, temporal relation with exposure to agent preceding effect and biological plausibility.
Results: There is a scarcity of randomized studies addressing the question, and the available studies all suffer from various forms of bias. However, there is some evidence suggesting that antidepressants given in addition to a mood stabilizer are not associated with an increased rate of switch when compared with the rate associated with the mood stabilizer alone.
Conclusion: When combined with a mood stabilizer, antidepressants given for acute bipolar depression seemingly do not induce a switch into hypomania or mania. Whether antidepressants may accelerate episode frequency and/or may cause other forms of destabilization in patients with bipolar disorder remain to be properly studied.