Thirty-one healthy male occasional cannabis smokers between 18 and 30 years of age and twenty-six male regular cannabis users participated in the study. Subjects were recruited through public advertisements at universities. The mean consumption of cannabis for the 3 months preceding inclusion in the study was set to a minimum of one joint per month and a maximum of less than one joint per week for the occasional smokers, and to a minimum of 10 joints per month for regular ones (Fabritius et al, 2013a). All volunteers had no history of neurological or psychiatric disorders. Nine occasional and one regular users were excluded from the research protocol for different reasons (claustrophobia, detection of brain anomalies, decision to drop out of the study, or technical problems during data processing). The final population selected for this study consists of 22 occasional cannabis smokers (median age 25 years, SD 2.8 years) and 25 regular users (median age 23 years, SD 2.2 years).
