We were able to tentatively link 124 of the identified susceptibility variations to potential functional mechanisms (Additional file 4). We expanded the genetics tag SNPs using haplotype data to detect the most likely nearly functional SNPs and genes. Besides fitting with the conventional idea that SNPs in coding regions may play important roles in disease susceptibility, the analyses presented here suggest that regulatory SNPs may also play important roles in addiction susceptibility. It will be interesting to study why and how natural selection shaped these cis-regulatory factors that potentially modulate addiction susceptibility.
