According to the results of a study published in JAMA Psychiatry, early-onset and late-onset cannabis use in adolescents was associated with subsequent psychotic experiences at age 18.
In this cohort study, data were evaluated for 5300 participants from the Avon Longitudinal Study of Parents and Children (56.1% women). Participants were born between 1991 and 1992 and measures of cigarette and cannabis use were collected at 6 time points between age 14 and 19. Participants were categorized as no cigarette or cannabis use, cigarette use only, or cannabis use with or without cigarette use. Psychotic experiences were evaluated between the age of 12 and 18 using the semi-structured psychosis-like symptom interview. The associations between substance use and psychotic experiences at age 12 and subsequent onset of psychotic experiences at age 18 were assessed.
Early-onset cigarette-only users (odds ratio [OR] 3.03) but not late-onset cigarette-only users (OR 0.84) had an increased risk for psychotic experiences at age 18. Moreover, both early-onset cannabis users (OR 3.79) and late-onset cannabis users (OR 3.05) had an increased risk for psychotic experiences at age 18.
After adjustment for sex, maternal education, emotional and behavioral problems at age 9, and maternal cigarette smoking during pregnancy, the association of early-onset cigarette-only use with subsequent psychotic experiences was attenuated (adjusted OR 1.78). Cannabis use, however, had a similar association with psychotic experiences after adjustment for both early-onset (adjusted OR 3.70) and late-onset cannabis use (adjusted OR 2.97).
Participants with definite psychotic experiences at age 12 were at increased odds of late-onset cigarette-only use (OR 1.76) and late-onset cannabis use (OR 1.66). No such association was reported between psychotic experiences at age 12 and early-onset substance use, but the researchers noted that “these classes had smaller membership.”
“Our study found that both adolescent cannabis use and cigarette use are associated with increased risk for subsequent psychotic experiences. This association was greater for cannabis,” the researchers wrote. “Associations observed between tobacco use and psychotic experiences are more likely than those for cannabis use to be influenced by other characteristics of people who develop psychotic experiences.”
Jones HJ, Gage SH, Heron J, et al. Association of combined patterns of tobacco and cannabis use in adolescence with psychotic experiences [published online January 17, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2017.4271