Cannabis is among the drugs with the highest frequency of (ab)use. About 1 in 5 Europeans aged 15–64 reported to have experimented with cannabis. In the United States the prevalence in ages 16–34 was estimated at 51.6 % (European Monitoring Centre for Drugs and Drug Addiction, 2012). Regular cannabis use has been associated with health problems, including mood and anxiety disorders (e.g., Cheung et al. 2010) and chronic bronchitis (Hall 2015; Joshi et al. 2014). Early onset and regular use during adolescence has possible effects on cognitive functioning (e.g., Crean et al. 2011) and predicts diminished educational (Horwood et al. 2010; Lynskey and Hall 2000) and professional attainment (Fergusson and Boden 2008; Volkow et al. 2014). Furthermore, recent evidence suggests that high-potency cannabis use elevates the risk of developing psychotic disorders (Di Forti et al. 2015, 2014). Namely, the odds of showing psychotic symptoms in individuals who declared to have ever used high-potency cannabis are about three times larger than in individuals who declared to have never used cannabis during their lifetime. The risk of showing psychotic symptoms is further
