There were 12 haplotypes with ≥ 0.01 frequency that accounted for 0.95 of the haplotype diversity. Only four haplotypes had a frequency ≥ 0.05 and these accounted for 0.79 of the haplotype diversity in the total sample: (a) 2222111 (0.30); (b) 1111222 (0.23); (c) 2112122 (0.15); and (d) 2111111 (0.11). The yin-yang haplotypes 2222111 and 1111222 correspond to the two haplotypes found in Caucasians and Asians (24). The 2112122 and 2111111 haplotypes are unique to individuals of African descent. Haplotype frequencies for each substance dependence group are given in Table 1. There were no differences in CTQ scores between the haplotypes (p = 0.34).
