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Does a history of cannabis use influence onset and course of schizophrenia?

Allebeck, Peter, Gunnarsson, Tove, Lundin, Andreas, Löfving, Sofia, Dal, Henrik and Zammit, Stanley ORCID: 2023. Does a history of cannabis use influence onset and course of schizophrenia? Acta Psychiatrica Scandinavica 147 (6) , pp. 614-622. 10.1111/acps.13562

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Introduction: While evidence strongly supports a causal effect of cannabis on psychosis, it is less clear whether the symptom pattern, clinical course, and outcomes differ in cases of schizophrenia with and without a background of cannabis use. Methods: Analysis of medical records from a longitudinal follow‐up of Swedish conscripts with data on cannabis use in adolescence and subsequent incidence of schizophrenia. One hundred sixty patients with schizophrenia were assessed using the OPCRIT protocol. Cases were validated for diagnosis schizophrenia according to OPCRIT. Results: Patients with a cannabis history (n = 32), compared to those without (n = 128), had an earlier age at onset, a higher number of hospital admissions and a higher total number of hospital days. There was no significant difference in type of onset and clinical symptom profiles between the groups. Conclusion: Our findings indicate that the disease burden of schizophrenia is greater in individuals who use cannabis during adolescence. Strengthening evidence on causality and teasing out long‐term effects of pre‐illness cannabis use from continued post‐illness has clinical implications for improving schizophrenia outcomes.

Item Type: Article
Date Type: Publication
Status: Published
Schools: MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Additional Information: License information from Publisher: LICENSE 1: URL:
Publisher: Wiley
ISSN: 0001-690X
Date of First Compliant Deposit: 25 April 2023
Date of Acceptance: 17 April 2023
Last Modified: 17 Oct 2023 08:37

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