Rates of psychiatric comorbidity among U.S. residents with lifetime cannabis dependence

Cannabis is the most widely used illegal drug in the U.S. population. Surveys have estimated that the lifetime prevalence rate for cannabis dependence is approximately 4%. Though the presence of a psychiatric disorder increases the likelihood of developing substance dependence, the field lacks data regarding the association between mental disorders and cannabis dependence. The aim of this study is to describe the prevalence of psychiatric disorders among individuals with cannabis dependence. The National Comorbidity Survey was used to obtain these data. We found that 90% of respondents with cannabis dependence had a lifetime mental disorder, compared to 55% without cannabis dependence. Alcohol dependence, antisocial personality disorder, and conduct disorder had the strongest associations with cannabis dependence, followed by anxiety and mood disorders. A large proportion of respondents with internalizing disorders developed mood or anxiety disorders prior to onset of their first cannabis dependence symptom. Data regarding the prevalence of comorbid mental disorders underscore the importance of thorough and systematic evaluation of patients seeking treatment for cannabis dependence. The failure to identify comorbidity may lead to inadequate treatment, and a poorer prognosis.