Cannabis use and vulnerability for psychosis in early adolescence—a TRAILS study

AIMS: To examine the direction of the longitudinal association between vulnerability for psychosis and cannabis use throughout adolescence. DESIGN: Cross-lagged path analysis was used to identify the temporal order of vulnerability for psychosis and cannabis use, while controlling for gender, family psychopathology, alcohol use and tobacco use. SETTING: A large prospective population study of Dutch adolescents the TRacking Adolescents' Individual Lives Survey (TRAILS) study. PARTICIPANTS: A total of 2120 adolescents with assessments at (mean) age 13.6, age 16.3 and age 19.1. MEASUREMENTS: Vulnerability for psychosis at the three assessment points was represented by latent factors derived from scores on three scales of the Youth Self-Report and the Adult Self-Report, i.e. thought problems, social problems and attention problems. Participants self-reported on cannabis use during the past year at all three waves. FINDINGS: Significant associations (r = 0.12-0.23) were observed between psychosis vulnerability and cannabis use at all assessments. Also, cannabis use at age 16 predicted psychosis vulnerability at age 19 (Z = 2.6, P < 0.05). Furthermore, psychosis vulnerability at ages 13 (Z = 2.0, P < 0.05) and 16 (Z = 3.0, P < 0.05) predicted cannabis use at, respectively, ages 16 and 19. CONCLUSIONS: Cannabis use predicts psychosis vulnerability in adolescents and vice versa, which suggests that there is a bidirectional causal association between the two.