Observational studies have consistently shown that recreational cannabis use is associated with an increased risk of psychosis — a condition that can cause delusions and hallucinations, making it challenging to determine what is reality. While observational studies can’t determine whether cannabis causes psychosis (as opposed to psychosis leading people to use cannabis), the current evidence seems to suggest it. If so, THC is the likely culprit.
Multiple longitudinal cohort studies around the world have generated similar results, finding a dose-dependent relationship between cannabis use and the development of psychosis, even when controlling for multiple confounders.[1][2][3][4][5] Additionally, the relationship does not seem to be influenced by whether someone has a history of psychotic symptoms.[6]
The risk of psychosis seems to be influenced by a number of factors, including the use of higher-potency cannabis (containing higher doses of THC), exposure early in life (i.e., adolescence), long-term cannabis use, and a family or personal history of psychosis.[7][1] Interestingly, a gene variant that influences how dopamine is metabolized in the brain has been linked to an increased risk of psychosis in adolescents exposed to cannabis.[8]
References
- ^Petrilli K, Ofori S, Hines L, Taylor G, Adams S, Freeman TPAssociation of cannabis potency with mental ill health and addiction: a systematic review.Lancet Psychiatry.(2022 Sep)
- ^Arseneault L, Cannon M, Poulton R, Murray R, Caspi A, Moffitt TECannabis use in adolescence and risk for adult psychosis: longitudinal prospective study.BMJ.(2002 Nov 23)
- ^Fergusson DM, Horwood LJ, Ridder EMTests of causal linkages between cannabis use and psychotic symptoms.Addiction.(2005 Mar)
- ^Zammit S, Allebeck P, Andreasson S, Lundberg I, Lewis GSelf reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: historical cohort study.BMJ.(2002 Nov 23)
- ^van Os J, Bak M, Hanssen M, Bijl RV, de Graaf R, Verdoux HCannabis use and psychosis: a longitudinal population-based study.Am J Epidemiol.(2002 Aug 15)
- ^Kuepper R, van Os J, Lieb R, Wittchen HU, Höfler M, Henquet CContinued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study.BMJ.(2011-Mar-01)
- ^Seffah KD, Kumar M, Naveen N, Pachchipulusu VK, Paudel Y, Patel A, Najam B, Desai HN, Illango J, Hamid PTo Weed or Not to Weed: A Systematic Review Exploring the Potential for Cannabis Use in Cardiovascular Disease, Mental Health and Pain Management.Cureus.(2023-Jun)
- ^Caspi A, Moffitt TE, Cannon M, McClay J, Murray R, Harrington H, Taylor A, Arseneault L, Williams B, Braithwaite A, Poulton R, Craig IWModeration of the effect of adolescent-onset cannabis use on adult psychosis by a functional polymorphism in the catechol-O-methyltransferase gene: longitudinal evidence of a gene X environment interaction.Biol Psychiatry.(2005-May-15)