Marijuana or cannabis is the most widely used illicit drug in the world (UNODC, 2014). Its recreational, non-medical, regular use might lead to dependence and have an adverse effect on the psychosocial development and mental health of adolescents and young adults. Regular marijuana use has been linked to an increased risk for psychotic symptoms and disorders, poor school performance and low educational attainment. Marijuana also has been considered a “gateway” drug, as marijuana users may be more likely than non-users to use other drugs such as cocaine and heroin (see review by Hall & Degenhardt, 2009).