The COMT Val158Met Polymorphism and Exploratory Behavior in Bipolar Mania.

Background: The catechol-O-methyltransferase (COMT) Val158Met gene influences cognition and behavior in psychiatric illnesses; its low-activity allele, methionine (Met), may be associated with behavior reflecting catecholamine overactivity. Heightened motor activity and increased positive valence are central features of bipolar disorder (BD) and have been quantified in the human Behavioral Pattern Monitor (hBPM), an exploration paradigm based upon the rodent open field. We examined whether hBPM behavior was related to the COMT gene in a small sample of manic BD patients.

Methods: Twenty-six acutely hospitalized manic BD patients were genotyped for the COMT Val158Met polymorphism and tested in the hBPM, an unfamiliar room containing novel objects. Movements around the hBPM and object interactions were video-recorded for 15 min and rated.

Results: Met homozygote BD patients demonstrated significantly more interactions with multiple objects and more time spent with objects in the hBPM. Valine (Val) homozygote patients exhibited the least object exploration, while heterozygote patients demonstrated intermediate levels.

Conclusion: This preliminary study suggests that arousal and positive valence are influenced in a linear fashion by COMT, presumably due to increased catecholamine in frontal regions, but these findings require replication in a larger sample. The hBPM can enable cross-species and transdiagnostic studies to inform neurobiology of psychiatric disorders.