analyses to males. Furthermore, we conducted our analyses on only the subsample of European American males (maximum N=250) in an effort to minimize concerns about population stratification since allele frequencies are known to differ across ethnicities. DNA was available for 186 European American males (74.4% of total), all of whom were successfully genotyped. Consistent with other estimates of allele frequencies at this locus (Caspi et al., 2002; Cohen et al., 2003), 68.8% of our sample was hemizygous for a high activity allele and 31.2% was hemizygous for a low activity allele.
