Daily Cannabis Use Linked to Earlier Psychosis Onset


Cannabis use is associated with an earlier age of psychosis onset, according to an article in Schizophrenia Bulletin, and daily use of high-potency cannabis is associated with an average of 6 years earlier onset than that of non-users.

Abstract →

Forti, M., Sallis, H., Allegri, F., Trotta, A.; Daily Use, Especially of High-Potency Cannabis, Drives the Earlier Onset of Psychosis in Cannabis Users. Schizophrenia Bulletin. Online December 17, 2013. doi: 10.1093/schbul/sbt181

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Kermit Cole
Kermit Cole, MFT, founding editor of Mad in America, works in Santa Fe, New Mexico as a couples and family therapist. Inspired by Open Dialogue, he works as part of a team and consults with couples and families that have members identified as patients. His work in residential treatment — largely with severely traumatized and/or "psychotic" clients — led to an appreciation of the power and beauty of systemic philosophy and practice, as the alternative to the prevailing focus on individual pathology. A former film-maker, he has undergraduate and master's degrees in psychology from Harvard University, as well as an MFT degree from the Council for Relationships in Philadelphia. He is a doctoral candidate with the Taos Institute and the Free University of Brussels. You can reach him at [email protected].


  1. From the research…”…daily users of high-potency cannabis had an onset an average of 6 years earlier than that of non-cannabis users. Conclusions: Daily use, especially of high-potency cannabis, drives the earlier onset of psychosis in cannabis users.”

    The relationship between marijuana and psychosis is still not clearly understood. However,after all of the research that has come out this year, it’s obvious that a relationship exists. With the coming legalization of marijuana throughout the western world, I expect an unfortunate jump in ‘psychosis’ will follow.

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  2. Two thoughts regarding cannabis and psychosis study.
    First, how much consideration is given Kantzian’s Self-Medication Hypothesis? Is it relevant?
    Second, in my area we are more successful controlling under-age access and use of legal psychoactive recreational products (tobacco and alcohol) than we are illegal substances. We need to improve both. The weak point in the former is when the substance is obtained by the young person from someone who got it legally. With legal substances we can police the original seller. And we have effective legal sanctions. Considering the number of people using cannabis and the costs incurred attempting to control it, we might consider legalizing it for those 21 years and older. Tax it, of course. Spend a significant percentage of the tax revenue of educating the public about the dangers of under-age use and abuse of all psychoactive substances. And among adolescents make cannabis use ‘uncool.’ It is an approach that has had reasonable success with tobacco. Our current approach does not seem to work well/ Can we honestly engage in a dialogue about alternatives?

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  3. Oxford JournalsMedicine Schizophrenia Bulletin Volume 37, Issue 3Pp. 631-639.

    Ana González-Pinto1,2, Susana Alberich2, Sara Barbeito2, Miguel Gutierrez2, Patricia Vega2, Berta Ibáñez3, Mahmoud Karim Haidar2, Eduard Vieta4 and Celso Arango5
    + Author Affiliations

    2Centro de Investigación Biomédica en Red de Salud Mental, Hospital Santiago Apóstol, University of the Basque Country, Vitoria, Spain
    3Basque Foundation for Health Innovation and Research, Vizcaya, BIOEF, CIBERESP, Sondica (Vizcaya), Spain
    4Bipolar Disorder Program, Institute of Neuroscience, Hospital Clinic, University of Barcelona, IDIBAPS, CIBERSAM, Barcelona, Spain
    5Adolescent Unit, Department of Psychiatry, Hospital General Universitario Gregorio Marañón, Centro de Investigación Biomédica en Red de Salud Mental, Madrid, Spain


    Objective: To examine the influence of cannabis use on long-term outcome in patients with a first psychotic episode, comparing patients who have never used cannabis with (a) those who used cannabis before the first episode but stopped using it during follow-up and (b) those who used cannabis both before the first episode and during follow-up. Methods: Patients were studied following their first admission for psychosis. They were interviewed at years 1, 3, and 5. At follow-up after 8 years, functional outcome and alcohol and drug abuse were recorded. Patients were classified according to cannabis use: 25 had cannabis use before their first psychotic episode and continuous use during follow-up (CU), 27 had cannabis use before their first episode but stopped its use during follow-up (CUS), and 40 never used cannabis (NU). Results: The 3 groups did not differ significantly in symptoms or functional outcome at baseline or during short-term follow-up. The CUS group exhibited better long-term functional outcome compared with the other 2 groups and had fewer negative symptoms than the CU group, after adjusting for potential confounders. For the CUS group, the effect size was 1.26 (95% confidence interval [CI] = 0.65 to 1.86) for functional outcome and −0.72 (95% CI = −1.27 to −0.14) for negative symptoms. All patients experienced improvements in positive symptoms during long-term follow-up. CONCLUSION:Cannabis has a deleterious effect, but stopping use after the first psychotic episode contributes to a clear improvement in outcome. The positive effects of stopping cannabis use can be seen more clearly in the long term.

    This Article
    Schizophr Bull (2011) 37 (3): 631-639.
    doi: 10.1093/schbul/sbp126
    First published online: November 13, 2009
    This article is Open Access
    » AbstractFree

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