Implication of the DGKH genotype in openness to experience, a premorbid personality trait of bipolar disorder.

Aims: The diacylglycerol kinase η gene (DGKH) is one of the few replicated risk genes for bipolar disorder. Meanwhile, specific personality traits, especially openness to experience, have been suggested as premorbid personality traits of the disorder. The aim of the present study was to examine the relation of the DGKH genotype with broad dimensions of personality, to obtain further evidence for its implication in the etiology of bipolar disorder.

Methods: The subjects were 319 Japanese healthy volunteers. Personality was assessed by the NEO Personality Inventory-Revised, which has the neuroticism, extraversion, openness to experience, agreeableness and conscientiousness dimensions. The A/G polymorphism of DGKH (rs9525580) was detected by a PCR-RFLP method. The subjects were divided into two groups with respect to the presence or absence of the A allele, which is a putative risk allele for bipolar disorder.

Results: The group with the A allele had significantly (p < 0.05) higher scores of openness to experience compared to that without this allele. Scores of other dimensions were not different between the two groups.

Limitations: The subjects had a homogeneous but rather specific background, and we did not employ a longitudinal design.

Conclusions: The present study shows that a bipolar-risk allele of DGKH is associated with higher openness to experience, providing further evidence for the implication of this gene in the etiology of bipolar disorder.