We performed the first genome wide association analysis on the Cloninger temperament scales Harm Avoidance, Novelty Seeking, Reward Dependence, and Persistence in a population sample of 5117 people from 2567 families. Although we had over 90% power to detect SNPs accounting for 1% of the variance in the scales, we detected no genome-wide significant SNPs for any scale. The SNPs in our dataset (including imputed SNPs) account for the vast majority of the common genetic variation in the population (Frazer, et al., 2007). Moreover, although we only had 26% power to detect common variants that account for 0.5% of the variance, if such variants comprised only half of the genetic variation for each trait, 40 such variants would be implied for a trait with heritability of 40%, implying that ten (i.e. 0.26*40) such variants should have been detectable per trait, yet we detected none across all traits. Therefore, our results suggest that the genetic architecture of personality consists of either very many common variants of very small effect size or rare variants (not tagged in our SNP chips), or both.
