Cannabis use can lead to social harms, including accidents, violence and suicide attempts (3), and regular cannabis use can lead to physical or psychological problems, and has been found to interfere with family, school, and work (4–8). Law enforcement, public health costs and loss of productivity and work potential due to health problems are also an economic drain on society (2, 5). According to the United Nations Office on Drugs and Crime (1), cannabis use is among the most common primary reasons for entering drug related treatment. Furthermore, cannabis use often precedes the use of other drugs, which suggests that cannabis may cause further problems as a gateway drug (9–11). However, the exact nature of the association between cannabis use and subsequent other illicit drug use is unclear (12–14).
