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Influence of cannabis use on incidence of psychosis in people at clinical high risk |
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| Authors: | Lucy A Chester MPharm Lucia R Valmaggia PhD Matthew J Kempton PhD Edward Chesney MD Dominic Oliver PhD Emily P Hedges PhD Elise Klatsa MSc Daniel Stahl PhD Mark van der Gaag PhD Lieuwe de Haan PhD Barnaby Nelson PhD Patrick McGorry PhD G Paul Amminger PhD Anita Riecher-Rössler PhD Erich Studerus PhD Rodrigo Bressan PhD Neus Barrantes-Vidal PhD Marie-Odile Krebs PhD Birte Glenthøj DMSc Merete Nordentoft PhD Stephan Ruhrmann PhD Gabriele Sachs PhD Philip McGuire PhD for the EU-GEI High Risk Study Group |
| Institution: | 1. Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK;2. Department of Psychology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK;3. Department of Biostatistics, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK;4. Faculty of Behavioural and Movement Sciences, Department of Clinical Psychology and EMGO+ Institute for Health and Care Research, VU University, Amsterdam, The Netherlands;5. Department Early Psychosis, Amsterdam UMC, Amsterdam, The Netherlands;6. Centre for Youth Mental Health, University of Melbourne, Parkville, Victoria, Australia;7. Faculty of Medicine, University of Basel, Basel, Switzerland;8. Department of Psychology, Division of Personality and Developmental Psychology, University of Basel, Basel, Switzerland;9. LiNC—Lab Interdisciplinar Neurociências Clínicas, Depto Psiquiatria, Escola Paulista de Medicina, Universidade Federal de São Paulo – UNIFESP, Sao Paulo, Brazil;10. Departament de Psicologia Clínica i de la Salut, Universitat Autònoma de Barcelona, Fundació Sanitària Sant Pere Claver (Spain), Spanish Mental Health Research Network (CIBERSAM), Barcelona, Spain;11. Hôpital Sainte-Anne, C'JAAD, Service Hospitalo-Universitaire, Inserm U894, Institut de Psychiatrie (CNRS 3557), University Paris Descartes, Paris, France;12. Centre for Neuropsychiatric Schizophrenia Research (CNSR) & Centre for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Mental Health Centre Glostrup, University of Copenhagen, Glostrup, Denmark;13. Mental Health Center Copenhagen and Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research, CINS, Mental Health Center Glostrup, Mental Health Services in the Capital Region of Copenhagen, University of Copenhagen, Kobenhavn, Denmark;14. Department of Psychiatry and Psychotherapy, Faculty of Medicine and University Hospital, University of Cologne, Cologne, Germany;15. Department of Psychiatry and Psychotherapy, Medical University of Vienna, Wien, Austria;16. EU-GEI collaborators and their affiliations are listed in the Acknowledgments section. |
| Abstract: | AimsEvidence for case–control studies suggests that cannabis use is a risk factor for the development of psychosis. However, there have been limited prospective studies and the direction of this association remains controversial. The primary aim of the present study was to examine the association between cannabis use and the incidence of psychotic disorders in people at clinical high risk of psychosis. Secondary aims were to assess associations between cannabis use and the persistence of psychotic symptoms, and with functional outcome.MethodsCurrent and previous cannabis use were assessed in individuals at clinical high risk of psychosis (n = 334) and healthy controls (n = 67), using a modified version of the Cannabis Experience Questionnaire. Participants were assessed at baseline and followed up for 2 years. Transition to psychosis and persistence of psychotic symptoms were assessed using the Comprehensive Assessment of At-Risk Mental States criteria. Level of functioning at follow up was assessed using the Global Assessment of Functioning disability scale.ResultsDuring follow up, 16.2% of the clinical high-risk sample developed psychosis. Of those who did not become psychotic, 51.4% had persistent symptoms and 48.6% were in remission. There was no significant association between any measure of cannabis use at baseline and either transition to psychosis, the persistence of symptoms, or functional outcome.ConclusionsThese findings contrast with epidemiological data that suggest that cannabis use increases the risk of psychotic disorder. |
| Keywords: | clinical high-risk longitudinal psychotic disorders substance use THC |