Our study was powered to detect almost all SNPs explaining at least 2% of phenotypic variation, and so our results effectively exclude the hypothesis that there are major loci affecting neuroticism in the Lausanne population. The lack of strong genetic association with EPQ-N score might imply that neuroticism is controlled by many loci each of relatively small effect, as is the case for many other complex phenotypes. There may also be important environmental interactions with risk factors not available in our study. If confirmed by additional studies, the suggestive age by genotype interaction that we report raises interesting methodological and biological questions.
