Time-varying effects in the strength of associations between cannabis use frequency and disorder and symptoms of psychosis, anxiety, and depression in adolescents and adults

Aims: We use time-varying effect models to examine the associations between cannabis use frequency and disorder and symptoms of psychosis, depression, and anxiety in a U.S. sample and a Canadian sample. Method: Data from two samples, the Victoria Healthy Youth Survey (V-HYS; six waves; ages 15 to 28) and the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC-III; cross-sectional; ages 18+) were restructured to model the time-varying effects of cannabis use frequency and disorder on symptoms of psychosis, depression, and anxiety across age. The moderating effects of sex and early onset (age 15 and younger) of cannabis use were also examined.

Results: Findings show significant, positive associations between cannabis use frequency and symptoms of psychosis and depression across most ages for both samples. Associations with anxiety symptoms were also significantly positive at most ages in the NESARC-III sample. In the V-HYS sample, cannabis use disorder was positively associated with psychotic, depressive, and anxiety symptoms in young adulthood and across most ages in the NESARC-III sample. Findings were not moderated by early onset of use. Interactions with sex show stronger associations for females than males, particularly in young adulthood.

Conclusions: Findings suggest that associations between cannabis and mental health are not specific to adolescents or young adults or only a concern as a result of early onset cannabis use, warranting further research into associations in adulthood.