One factor impeding genetic studies of cannabis use disorders may be problems in identifying and ascertaining cases. First, treatment seeking specifically for cannabis use disorders remains relatively rare [152,153]. Secondly, among those seeking treatment for cannabis-related problems a relatively large number of younger cases may be coerced into treatment either though contact with the justice system or as a result of workforce detection. This may result in a situation in some of those seeking treatment for “cannabis problems” report limited cannabis use and so may not be ideal cases for genetic studies [154]. Additionally, other substance use disorders and psychiatric disorders are highly prevalent in individuals seeking treatment for a cannabis use disorder. This suggests that treatment samples may not provide the optimal sampling frame for studying cannabis use disorders.
