Sleep as a Mediator Between Cannabis Use and Psychosis Vulnerability: A Longitudinal Cohort Study.

Objectives: Increasing evidence implicates cannabis consumption as a key risk factor in the development of psychosis, but the mechanisms underpinning this relationship remain understudied. This study proposes to determine whether sleep disruption acts as a mediator of the cannabis-to-psychosis relationship. Study Design: This longitudinal study assessed measures of cannabis use frequency, sleep quality (SQ), and psychotic-like experiences (PLEs) were collected using self-reported questionnaires. Data were collected from September 2012 to September 2018. Data were collected from a general population sample of adolescents who entered the seventh grade in 31 schools in the Greater Montreal area. The study uses data collected on an annual basis from 3801 high school students from grades 7 to 11. The aforementioned measures were measured using the Detection of Alcohol and Drug Problems in Adolescents questionnaire, a SQ Likert scale, and measures the Psychotic-Like Experiences Questionnaire for Children. Study Results: Results show a reciprocal 1-year cross-lagged effect of cannabis use and sleep (ß = -0.076, 95% CI = -0.037 to -0.018, P = .000), of sleep on cannabis use (ß = -.016, 95% CI = -0.025 to -0.006, P = .007), of sleep on PLEs (ß = -0.077, 95%CI = -0.014 to -0.051, P = .000), and of PLEs on sleep (ß = -0.027, 95% CI = -0.037 to -0.018, P = .000). We additionally found a 2 years indirect lagged-effect of cannabis use on PLEs (ß = 0.068, 95% CI = 0.024 to 0.113, P = .011) mediated by 1-year sleep (ß = 0.006, 95% CI = 0.003 to 0.009, P = .001). Conclusions: Our results suggest sleep disruptions simultaneously aggravate, and are aggravated by, cannabis addiction and PLEs. The longitudinal sleep-mediated effect of cannabis use on PLEs encourages further research into the role of sleep as a potential therapeutic target in the prevention of cannabis-related psychosis.