Progressing from occasional marijuana use to weekly or daily use increases an adolescent’s risk of recurrent psychotic-like experiences (PLE) by 159 per cent, according to research published in the Journal of Child Psychology and Psychiatry . The link between marijuana use and PLE (perceptual aberration, ideas with unusual content and feelings of persecution) was best explained by emerging symptoms of depression.
Researchers at the Université de Montréal in Canada carried out yearly assessments of cognitive development, substance use and psychiatric disorders among approximately 2,566 adolescents, and identified three trajectories of PLE: low decreasing, high decreasing, and moderate increasing.
A steeper growth in cannabis use was associated with a higher likelihood of being assigned to the moderate increasing trajectory group (odds ratio 2.59; 95% CI 1.11–6.03). Growth in depression symptoms, not anxiety or change in cognitive functioning, mediated the relationship between growth in cannabis use and the PLE moderate increasing group.
Commenting on the findings, the authors said: “Depression symptoms partially mediated the longitudinal link between cannabis use and PLE in adolescents, suggesting that there may be a preventative effect to be gained from targeting depression symptoms, in addition to attempting to prevent cannabis use in youth presenting increasing psychotic experiences.”