Objective: Genome-wide association study was carried out on personality traits among bipolar patients as possible endophenotypes for gene discovery in bipolar disorder.
Methods: The subscales of Cloninger's Temperament and Character Inventory (TCI) and the Zuckerman–Kuhlman Personality Questionnaire (ZKPQ) were used as quantitative phenotypes. The genotyping platform was the Affymetrix 6.0 SNP array. The sample consisted of 944 individuals for TCI and 1007 for ZKPQ, all of European ancestry, diagnosed with bipolar disorder by Diagnostic and Statistical Manual of Mental Disorders-IV criteria.
Results: Genome-wide significant association was found for two subscales of the TCI, rs10479334 with the ‘Social Acceptance versus Social Intolerance’ subscale (Bonferroni P=0.014) in an intergenic region, and rs9419788 with the ‘Spiritual Acceptance versus Rational Materialism’ subscale (Bonferroni P=0.036) in PLCE1 gene. Although genome-wide significance was not reached for ZKPQ scales, lowest P values pinpointed to genes, RXRG for Sensation Seeking, GRM7 and ITK for Neuroticism Anxiety, and SPTLC3 gene for Aggression Hostility.
Conclusion: After correction for the 25 subscales in TCI and four scales plus two subscales in ZKPQ, phenotype-wide significance was not reached.