We have presented the results of this first GWA study of all five major dimensions of personality assessed with the NEO-PI-R, a comprehensive, reliable, and widely used measure of the Five-Factor Model. Compared with the existing literature (and especially with the candidate gene studies), a major strength is the sample size of about 4,000 individuals included in the GWA analyses. A further contribution to increased signal/noise ratio is provided by the relative homogeneity of this sample from a founder population in Sardinia. The GWA approach offers a new opportunity for a systematic search of the genetic underpinnings of personality traits. These data might become even more valuable with the accumulation of GWA results from multiple samples, as for other traits and diseases (11, 87, 88). To provide some initial evidence of association beyond our Sardinian cohort, a selected number of top signals from the GWA analyses were typed in two independent samples. Although replication attempts clearly failed to find consistent effects for most SNPs we examined, a few provided more convincing evidence. In particular, the association of Agreeableness with the
