Cannabis use disorder in relation to socioeconomic factors and psychiatric comorbidity: A cluster analysis of three million individuals born in 1970–2000

BACKGROUND: Cannabis use disorder (CUD) is one of the main reasons for seeking substance use treatment. It is thus important to monitor and increase knowledge of individuals with CUD utilizing healthcare. We aimed to examine the number of CUD diagnoses over time, compare individuals with CUD with those without and identify subgroups based on CUD diagnosis, sex, birth year, socioeconomic factors and psychiatric comorbidity. METHODS: A Swedish, population-based study with 3,307,759 individuals, born in 1970–2000, with register data extending to 2016. K-mode cluster analysis was used to identify potential subgroups. RESULTS: The number of individuals with a CUD diagnosis was 14,046 (0.42%). CUD diagnoses increased over time (born 1990–1994: 61 per 100,000, born 1995–2000: 107 per 100,000, by 2016). A majority of those with a CUD had another psychiatric diagnosis (80%, compared with 19% for those without CUD). Four clusters were identified. Cluster 1 comprised mainly men with low income and substance use disorders, clusters 2, 3 and 4 comprised mainly women with higher proportions of mood-related, neurotic and stress-related and behavioural disorders. CONCLUSIONS: There was an increase in CUD diagnoses in Sweden over time, especially among younger birth cohorts. Individuals with CUD were more often male, from younger birth cohorts, with lower education and income than those without CUD. Men and women with CUD exhibited differences in education, income and psychiatric comorbidity. Our results demonstrate the importance of monitoring the impact of socioeconomic factors and psychiatric comorbidity in relation to CUD.