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Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study

Schoeler, T; Petros, N; Di Forti, M; Klamerus, E; Foglia, E; Ajnakina, O; Gayer-Anderson, C; ... Bhattacharyya, S; + view all (2016) Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study. The Lancet Psychiatry , 3 (10) pp. 947-953. 10.1016/S2215-0366(16)30188-2. Green open access

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Abstract

BACKGROUND: Although cannabis use after a first episode of psychosis has been associated with relapse, little is known about the determinants of this most preventable risk factor for relapse of psychosis. Here we aimed to study whether the effects on outcome vary depending on the type of cannabis consumed and usage pattern. METHODS: In this observational study, we prospectively recruited and followed up patients aged 18–65 years who presented with their first episode of psychosis to psychiatric services in south London, London, UK. Relapse of psychosis within 2 years after onset of psychosis was defined as risk of subsequent admission to hospital. We classified patients into different patterns of cannabis use based on continuity of use after onset of psychosis, potency of cannabis consumed, and frequency of use after the onset of their illness. We used multiple regression analyses (logistic or binominal) to compare the different cannabis use groups and propensity score analysis to validate the results. FINDINGS: Between April 12, 2002, and July 26, 2013, 256 patients presented with a first episode of psychosis. We did follow-up assessments for these patients until September, 2015. Simple analyses showed that former regular users of cannabis who stopped after the onset of psychosis had the most favourable illness course with regards to relapse. In multiple analysis, continued high-frequency users (ie, daily use in all 24 months) of high-potency (skunk-like) cannabis had the worst outcome, indexed as an increased risk for a subsequent relapse (odds ratio [OR] 3·28; 95% CI 1·22–9·18), more relapses (incidence rate ratio 1·77; 95% CI 0·96–3·25), fewer months until a relapse occurred (b −0·22; 95% CI −0·40 to −0·04), and more intense psychiatric care (OR 3·16; 95% CI 1·26–8·09) after the onset of psychosis. INTERPRETATION: Adverse effects associated with continued use of cannabis after the onset of a first episode of psychosis depend on the specific patterns of use. Possible interventions could focus on persuading cannabis-using patients with psychosis to reduce use or shift to less potent forms of cannabis. FUNDING: National Institute for Health Research (NIHR).

Type: Article
Title: Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/S2215-0366(16)30188-2
Publisher version: http://dx.doi.org/10.1016/S2215-0366(16)30188-2
Language: English
Additional information: © The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY license.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Div of Psychology and Lang Sciences > Clinical, Edu and Hlth Psychology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Division of Psychiatry
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Epidemiology and Health
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Epidemiology and Health > Behavioural Science and Health
URI: https://discovery.ucl.ac.uk/id/eprint/1556732
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