Cannabis is widely used, with cumulative lifetime incidence of use estimated to range from 6%-20% in Europe, 3%-11% in the Middle East and Africa, and exceeding 40% in the US and New Zealand (Degenhardt et al., 2008). Lifetime prevalence of cannabis use in Australian adolescents has been estimated at 60% (Patton et al., 2002). Although many individuals use cannabis infrequently and without experiencing problems, globally an estimated 13.1 million individuals meet criteria for cannabis dependence, contributing 10.3% of the illicit drug use global burden of disease (Degenhardt et al., 2014). It is estimated 10% −16% of cannabis users develop dependence (Anthony, 2006), but before progressing to dependence individuals must pass through a number of preceding stages. Examining the multiple stages of drug use before dependence develops is necessary for gaining a comprehensive understanding of factors involved in drug use, and for identifying opportunities for early intervention (Hines et al., 2015a).
