In the same study on all twins and siblings in our phenotypic dataset evidence was found for sex differences in the source of genetic variation for Harm Avoidance and Reward Dependence (Keller, et al., 2005), implying that partly different genetic factors explain variance in these scales for males and females. Therefore, for these two scales we ran the GWA analysis separately for males and females, as well as for the sample as a whole.
