The most significant effect across the five factors was found between rs644148 and Openness (P = 9.44 × 10−7). This same SNP was strongly associated with Extraversion as well. Although Openness and Extraversion are correlated, we observed only a modest overlap between association results for the two traits. For example, among markers that were associated with Extraversion at p < .001, less than 5% were also associated with Openness at a similar significance level (and vice-versa). The overlap was even more reduced at more stringent significance levels, indicating that the association between rs644148 and the two traits is quite exceptional. We were unable to type this SNP in the replication samples, but a nearby SNP (rs565819; LD =1) was genotyped in the US sample and no association was found. Among the other high ranked associations for Openness there is an intriguing association with rs10251794 (P = 3.43 × 10−5), an intronic SNP in CNTNAP2, which encodes for the member of the neurexin family that has been linked with autism (68-70) and a complex phenotype of schizophrenia, epilepsy, and cognitive impairment
