Pharmacogenomics of antidepressant induced mania: A review and meta-analysis of the serotonin transporter gene (5HTTLPR) association

Background: Antidepressants can trigger a rapid mood switch from depression to mania. Identifying genetic risk factors associated with antidepressant induced mania (AIM) may enable individualized treatment strategies for bipolar depression. This review and meta-analysis evaluates the evidence for association between the serotonin transporter gene promoter polymorphism (5HTTLPR) and AIM. Methods: Medline up to November 2009 was searched for key words bipolar, antidepressant, serotonin transporter, SLC6A4, switch, and mania. Results: Five studies have evaluated the SLC6A4 promoter polymorphism and AIM in adults (total N= 340 AIM+ cases, N = 543 AIM - controls). Although a random effects meta-analysis showed weak evidence of association of the S allele with AIM+ status, a test of heterogeneity indicated significant differences in estimated genetic effects between studies. A similar weak association was observed in a meta-analysis based on a subset of three studies that excluded patients on mood stabilizers; however the result was again not statistically significant. Limitations: Few pharmacogenomic studies of antidepressant treatment of bipolar disorder have been published. The completed studies were underpowered and often lacked important phenotypic information regarding potential confounders such as concurrent use of mood stabilizers or rapid cycling. Conclusions: There is insufficient published data to confirm an association between 5HTTLPR and antidepressant induced mania. Pharmacogenomic studies of antidepressant induced mania have high potential clinical impact provided future studies are of adequate sample size and include rigorously assessed patient characteristics (e.g. ancestry, rapid cycling, concurrent mood stabilization, and length of antidepressant exposure). (C) 2011 Elsevier B.V. All rights reserved.