In the other previous study in which genetic associations were detected, all participants were males [18]. As this study did, we found allelic and genotypic associations in our male subsample. However, the female participation in our study was useful because it indicated that the genotypic association was not gender related, whereas the allelic association was indeed male-limited. The latter association could be related to the finding that nonspecific genetic factors account for much more variance percentage of illicit opioid use in males (37%) [4] than in females (3%)[3].
