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

Abstract 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.