The accumulating evidence has developed a consensus on the validity of cannabis withdrawal and the need to include it in DSM-V. 22, 25, 26 However, the epidemiology of cannabis withdrawal in the general population remains entirely unknown. This information is important for several reasons. First, if cannabis withdrawal occurs only among a small minority of frequent cannabis users in the general population, then its public health significance is limited. However, if withdrawal is common among frequent cannabis users, this is important knowledge to disseminate to clinicians and to the general public. Second, some previous studies were based on clinic patients, who are often polysubstance abusers, so the withdrawal symptoms they attributed to cannabis may have been due to other drugs. Third, many studies of untreated cannabis users have been small (e.g., samples of 30, 16 12, 17 and 18, 18) potentially leading to unstable results. Fourth, while laboratory studies have provided the fundamental data identifying the cannabis withdrawal syndrome, it is possible that individuals willing to spend several days in an inpatient setting or to visit a laboratory every day
