The COMT enzyme enables the degradation of brain monoamines such as Dopamine and is encoded by a single gene for which several polymorphisms are known, including the Val158Met polymorphism which has been widely studied in various psychiatric disorders, including addictions, as well as in impulsivity. In most studies it is the Val allele which is found to be associated with addictive behaviors. The study METHADOSE, which began in 2009, includes opiate-dependent patients substituted by methadone. The preliminary analysis of this study shows a genotype distribution different from that of general population samples, with a greater prevalence of Val / Val and Val / Met genotypes. Will be included in the COM ON study subjects who have consumed illicit opiates (heroin, methadone, buprenorphine or morphine) more than 10 times in their life, without ever having the DSM-IV criteria for opiate dependence or abuse. The study will compare, by means of saliva samples, Val / Val and Val / Met genotypes between the subjects recruited in COM ON and those recruited in METHADOSE. Will also be included auto-questionnaires to identify psychological factors that may constitute risk or protective factors vis-à-vis the development of dependence.