Early evidence has been mixed. There have been three published GWA studies on personality traits - two on Neuroticism and one assessing all Big Five traits. Van den Oord et al. (2008) found potential association between variants in the MAMDC1 gene and Neuroticism, and Shifman et al. (2008) found suggestive association between the PDE4D gene and Neuroticism, which was replicated in one sample, but failed to replicate in two other samples. Terracciano et al. (2008) found potential association signals for all five scales, but the effect sizes were small and most of the associations failed to replicate in their follow-up samples. GWA has yet to be applied to Cloninger’s temperament scales, which could better reflect genetic influences given their purported basis in psychobiological experiments and theory.
