supporting the homogeneity of the study sample. However, we would like to point out, that the most significant associations were observed for those items that particularly describe social learning. Association with weak learning from social feedback would seem very logical for different frontal cortex genetic regulation, but it may also reflect those in cerebellum. It has also been reported that 21–45% of the prison inmates have a comorbid ADHD,52, 53 and a shared etiology has been suggested for such externalizing phenotypes as adult substance use and antisocial personality, and childhood conduct disorder and ADHD.54, 55, 56 ADHD was not diagnosed in our study sample, however, ~96% of the analyzed sample were substance abusers. The externalizing dimension of behavior is hypothesized to reflect an inherited predisposition for developing one or more of the aforementioned disorders.57 Thus, the previous findings on reduced GMV in frontal brain areas associated with ASPD may also reflect the comorbidity of the externalizing problems, consistent with the findings of ADHD prevalence in prisoners and supported by our findings here.
