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Schizophrenia Bulletin Advance Access published online on November 13, 2009
Schizophrenia Bulletin, doi:10.1093/schbul/sbp126
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© The Authors 2009. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Cannabis and First-Episode Psychosis: Different Long-term Outcomes Depending on Continued or Discontinued Use

Ana González-Pinto1,2, Susana Alberich2, Sara Barbeito2, Miguel Gutierrez2, Patricia Vega2, Berta Ibáñez3, Mahmoud Karim Haidar2, Eduard Vieta4 and Celso Arango5
2 Centro de Investigación Biomédica en Red de Salud Mental, Hospital Santiago Apóstol, University of the Basque Country, Vitoria, Spain
3 Basque Foundation for Health Innovation and Research, Vizcaya, BIOEF, CIBERESP, Sondica (Vizcaya), Spain
4 Bipolar Disorder Program, Institute of Neuroscience, Hospital Clinic, University of Barcelona, IDIBAPS, CIBERSAM, Barcelona, Spain
5 Adolescent Unit, Department of Psychiatry, Hospital General Universitario Gregorio Marañón, Centro de Investigación Biomédica en Red de Salud Mental, Madrid, Spain

1 To whom correspondence should be addressed; Department of Psychiatry, Centro de Investigación Biomédica en Red de Salud Mental, Hospital Santiago Apóstol, University of the Basque Country, Olaguibel 29, Vitoria, Spain; tel: +34-945-007770, fax: +34-945-007764, e-mail: ANAMARIA.GONZALEZ-PINTOARRILLAGA{at}osakidetza.net.

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.

Keywords: cannabis / first-episode psychosis / outcome / follow-up / discontinued use


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