For the purposes of this review, we refer to substance use disorder as addiction. This term will encompass diagnostic definitions derived from the DSM as well as other diagnostic schema, such as the International Classification of Diseases (e.g., ICD-10) [4] and the Fagerström measures of nicotine dependence (e.g., FTND, FTQ) [5]. The overwhelming majority of the research presented in this review comes from genetic association studies of alcohol, tobacco, and cannabis, with brief mention of emerging research on cocaine and opioids.
