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Continued versus discontinued cannabis use in patients with psychosis: a systematic review and meta-analysis

Schoeler, Tabea; Monk, Anna; Sami, Musa B.; Klamerus, Ewa; Foglia, Enrico; Brown, Ruth; Camuri, Giulia; Altamura, A Carlo; Murray, Robin; Bhattacharyya, Sagnik

Continued versus discontinued cannabis use in patients with psychosis: a systematic review and meta-analysis Thumbnail


Authors

Tabea Schoeler

Anna Monk

Musa B. Sami

Ewa Klamerus

Enrico Foglia

Ruth Brown

Giulia Camuri

A Carlo Altamura

Robin Murray

Sagnik Bhattacharyya



Abstract

Background: Although the link between cannabis use and development of psychosis is well established, less is known about the effect of continued versus discontinued cannabis use after the onset of psychosis. We aimed to summarise available evidence focusing on the relationship between continued and discontinued cannabis use after onset of psychosis and its relapse. Methods: In this systematic review and meta-analysis, we searched MEDLINE for articles published in any language from the database inception date up until April 21, 2015 that included a sample of patients with a pre-existing psychotic disorder with a follow-up duration of at least 6 months. We used a combination of search terms for describing cannabis, the outcome of interest (relapse of psychosis), and the study population. We excluded studies if continued cannabis use or discontinued cannabis use could not be established. We compared relapse outcomes between those who continued (CC) or discontinued (DC) cannabis use or were non-users (NC). We used summary data (individual patient data were not sought out) to estimate Cohen's d, which was entered into random effects models (REM) to compare CC with NC, CC with DC, and DC with NC. Meta-regression and sensitivity analyses were used to address the issue of heterogeneity. Findings: Of 1903 citations identified, 24 studies (16 565 participants) met the inclusion criteria. Independent of the stage of illness, continued cannabis users had a greater increase in relapse of psychosis than did both non-users (dCC-NC=0·36, 95% CI 0·22-0·50, p<0·0001) and discontinued users (dCC-DC=0·28, 0·12-0·44, p=0·0005), as well as longer hospital admissions than non-users (dCC-NC=0·36, 0·13 to 0·58, p=0·02). By contrast, cannabis discontinuation was not associated with relapse (dDC-NC=0·02, -0·12 to 0·15; p=0·82). Meta-regression suggested greater effects of continued cannabis use than discontinued use on relapse (dCC-NC=0·36 vs dDC-NC=0·02, p=0·04), positive symptoms (dCC-NC=0·15 vs dDC-NC=-0·30, p=0·05) and level of functioning (dCC-NC=0·04 vs dDC-NC=-0·49, p=0·008) but not on negative symptoms (dCC-NC=-0·09 vs dDC-NC=-0·31, p=0·41). Interpretation: Continued cannabis use after onset of psychosis predicts adverse outcome, including higher relapse rates, longer hospital admissions, and more severe positive symptoms than for individuals who discontinue cannabis use and those who are non-users. These findings point to reductions in cannabis use as a crucial interventional target to improve outcome in patients with psychosis.

Citation

Schoeler, T., Monk, A., Sami, M. B., Klamerus, E., Foglia, E., Brown, R., …Bhattacharyya, S. (2016). Continued versus discontinued cannabis use in patients with psychosis: a systematic review and meta-analysis. Lancet Psychiatry, 3(3), 215-225. https://doi.org/10.1016/s2215-0366%2815%2900363-6

Journal Article Type Article
Acceptance Date Jul 25, 2015
Online Publication Date Jan 14, 2016
Publication Date Mar 1, 2016
Deposit Date Jul 6, 2020
Publicly Available Date Mar 28, 2024
Journal The Lancet Psychiatry
Print ISSN 2215-0366
Electronic ISSN 2215-0374
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 3
Issue 3
Pages 215-225
DOI https://doi.org/10.1016/s2215-0366%2815%2900363-6
Public URL https://nottingham-repository.worktribe.com/output/4752737
Publisher URL https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(15)00363-6/fulltext
Additional Information © 2016 Elsevier Ltd. All rights reserved.

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