Pharmacogenetics of bipolar disorder

Pharmacogenetics and bipolar disorder

Bipolar disorder (BD) is a major psychiatric condition that commonly requires prophylactic and episodic treatment. There is important variability in the therapeutic response and side-effect profiles to currently available pharmacological agents. Pharmacogenetics have provided new hopes to develop more efficient treatment strategies tailored to the individual patient's needs. This review assesses nonsystematically studies using pharmacogenetic strategies in BD. Most of these studies have focused on patients selected according to lithium response, and more recently, a growing number of studies have been investigating genetic factors in mixed samples of patients classified according to response to antidepressant treatment. Although previous clinical and family studies support the use of pharmacogenetic strategies both to increase phenotype homogeneity as well as to identify genetic factors that may mediate response to treatment, most molecular studies carried out to date are still preliminary and in need of external validation. A major problem has been comparability between studies, in part, because of differences in the criteria used to define response. More attention should be paid to standardize the criteria for drug response definition.

Long-term responsiveness to lithium as a pharmacogenetic outcome variable: treatment and etiologic implications

The importance of genes in the etiology of bipolar disorder has been substantiated through family, twin, and adoption studies. Bipolar disorder is treated at the prophylactic and episodic levels; lithium is one of the most common forms of prophylactic treatment. Recently, pharmacogenetics has come to play an active role in the elucidation of genetic factors that may play a role in modulating lithium response. This strategy has provided hope for advancements in understanding the genetics of lithium-responsive bipolar disorder. This review encompasses studies that have used populations of lithium responders and non-responders to carry out family, linkage, or association studies, as well as some insight into possible mechanisms by which lithium produces its prophylactic effect. Although data examining the pharmacogenetics of bipolar disorder remain scarce, this is a promising avenue of investigation to help genetically define more homogeneous populations or to search for genetic predictors of drug response.