Age‐varying effects of cannabis use frequency and disorder on symptoms of psychosis, depression and anxiety in adolescents and adults

AIMS: We tested the age‐varying associations of cannabis use (CU) frequency and disorder (CUD) with psychotic, depressive and anxiety symptoms in adolescent and adult samples. Moderating effects of early onset (≤ 15 years) and sex were tested. DESIGN: Time‐varying effect models were used to assess the significance of concurrent associations between CU and CUD and symptoms of psychosis, depression and anxiety at each age. SETTING AND PARTICIPANTS: Adolescent data (V‐HYS; n = 662) were collected from a randomly recruited sample of adolescents in Victoria, British Columbia, Canada during a 10‐year period (2003–13). Adult cross‐sectional data (NESARC‐III; n = 36 309) were collected from a representative sample from the United States (2012–13). MEASUREMENTS: Mental health symptoms were assessed using self‐report measures of diagnostic symptoms. CU was based on frequency of past‐year use. Past‐year CUD was based on DSM‐5 criteria. FINDINGS: For youth in the V‐HYS, CU was associated with psychotic symptoms following age 22 [b = 0.13, 95% confidence interval (CI) = 0.002, 0.25], with depressive symptoms from ages 16–19 and following age 25 (b = 0.17, 95% CI = 0.003, 0.34), but not with anxiety symptoms. CUD was associated with psychotic symptoms following age 23 (b = 0.51, 95% CI = 0.01, 1.01), depressive symptoms at ages 19–20 and following age 25 (b = 0.71, 95% CI = 0.001, 1.42) and anxiety symptoms ages 26–27 only. For adults in the NESARC‐III, CU was associated with mental health symptoms at most ages [e.g. psychotic symptoms; age 18 (b = 0.22, 95% CI = 0.10, 0.33) to age 65 (b = 0.36, 95% CI = 0.16, 0.56)]. CUD was associated with all mental health symptoms across most ages [e.g. depressive symptoms; age 18 (b = 0.96, 95% CI = 0.19, 1.73) to age 61 (b = 1.11, 95% CI = 0.01, 2.21)]. Interactions with sex show stronger associations for females than males in young adulthood [e.g. V‐HYS: CUD × sex interaction on psychotic symptoms significant after age 26 (b = 1.12, 95% CI = 0.02, 2.21)]. Findings were not moderated by early‐onset CU. CONCLUSIONS: Significant associations between cannabis use (CU) frequency and disorder (CUD) and psychotic and depressive symptoms in late adolescence and young adulthood extend across adulthood, and include anxiety.