This paper aims to provide a review of the existing research on human genetic studies of opioid dependence, focusing on the most prominent genes reported in the literature. Twin and candidate gene studies will be the target of this review A brief description of the epidemiology and biological mechanisms will serve as background information that is central to the focus of the paper. Next, we will discuss the behavioural and psychological characteristics associated with opioid dependence in light of human genetic studies reviewed here.
