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Lancet Psychiatry. 2019 May;6(5):427-436. doi: 10.1016/S2215-0366(19)30048-3. Epub 2019 Mar 19.

The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study.

Author information

1
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, UK; National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London, UK; South London and Maudsley NHS Mental Health Foundation Trust, London, UK. Electronic address: marta.diforti@kcl.ac.uk.
2
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, UK; National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London, UK; South London and Maudsley NHS Mental Health Foundation Trust, London, UK.
3
Addiction and Mental Health Group (AIM), Department of Psychology, University of Bath, Bath, UK.
4
Institute of Psychiatry, Psychology and Neuroscience and Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK.
5
Department of Health Service and Population Research, Institute of Psychiatry, King's College London, London, UK.
6
Department of Psychiatry, University of Cambridge, Cambridge, UK; Psylife Group, Division of Psychiatry, University College London, London, UK.
7
Department of Experimental Biomedicine and Clinical Neuroscience, University of Palermo, Palermo, Italy.
8
Department of Medical and Surgical Science, Psychiatry Unit, Alma Mater Studiorum Università di Bologna, Bologna, Italy.
9
INSERM U955, Equipe 15, Institut National de la Santé et de la Recherche Médicale, Créteil, Paris, France.
10
Department of Child and Adolescent Psychiatry, Hospital General Universitario Gregorio Marañón, School of Medicine, Universidad Complutense, IiSGM (CIBERSAM), Madrid, Spain.
11
Etablissement Public de Santé Maison Blanche, Paris, France.
12
Department of Psychiatry, Early Psychosis Section, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands.
13
Barcelona Clinic Schizophrenia Unit, Neuroscience Institute, Hospital clinic, Department of Medicine, University of Barcelona, IDIBAPS, CIBERSAM, Barcelona, Spain.
14
Division of Psychiatry, Department of Neuroscience and Behaviour, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
15
Department of Preventative Medicine, Faculdade de Medicina FMUSP, University of São Paulo, São Paulo, Brazil.
16
Rivierduinen Institute for Mental Health Care, Leiden, Netherlands.
17
Department of Psychiatry, University of Cambridge, Cambridge, UK; CAMEO Early Intervention Service, Cambridgeshire & Peterborough NHS Foundation Trust, Cambridge, UK.
18
Psylife Group, Division of Psychiatry, University College London, London, UK.
19
Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, South Limburg Mental Health Research and Teaching Network, Maastricht University Medical Centre, Maastricht, Netherlands.
20
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, UK; Centre for Genomic Sciences, Li KaShing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
21
Institute of Psychiatry, Psychology and Neuroscience and Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK; Brain Centre Rudolf Magnus, Utrecht University Medical Centre, Utrecht, The Netherlands.
22
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, London, UK; National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London, UK.
23
Department of Addiction, Institute of Psychiatry, King's College London, London, UK.
24
Institute of Psychiatry, Psychology and Neuroscience and Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK; South London and Maudsley NHS Mental Health Foundation Trust, London, UK.

Abstract

BACKGROUND:

Cannabis use is associated with increased risk of later psychotic disorder but whether it affects incidence of the disorder remains unclear. We aimed to identify patterns of cannabis use with the strongest effect on odds of psychotic disorder across Europe and explore whether differences in such patterns contribute to variations in the incidence rates of psychotic disorder.

METHODS:

We included patients aged 18-64 years who presented to psychiatric services in 11 sites across Europe and Brazil with first-episode psychosis and recruited controls representative of the local populations. We applied adjusted logistic regression models to the data to estimate which patterns of cannabis use carried the highest odds for psychotic disorder. Using Europe-wide and national data on the expected concentration of Δ9-tetrahydrocannabinol (THC) in the different types of cannabis available across the sites, we divided the types of cannabis used by participants into two categories: low potency (THC <10%) and high potency (THC ≥10%). Assuming causality, we calculated the population attributable fractions (PAFs) for the patterns of cannabis use associated with the highest odds of psychosis and the correlation between such patterns and the incidence rates for psychotic disorder across the study sites.

FINDINGS:

Between May 1, 2010, and April 1, 2015, we obtained data from 901 patients with first-episode psychosis across 11 sites and 1237 population controls from those same sites. Daily cannabis use was associated with increased odds of psychotic disorder compared with never users (adjusted odds ratio [OR] 3·2, 95% CI 2·2-4·1), increasing to nearly five-times increased odds for daily use of high-potency types of cannabis (4·8, 2·5-6·3). The PAFs calculated indicated that if high-potency cannabis were no longer available, 12·2% (95% CI 3·0-16·1) of cases of first-episode psychosis could be prevented across the 11 sites, rising to 30·3% (15·2-40·0) in London and 50·3% (27·4-66·0) in Amsterdam. The adjusted incident rates for psychotic disorder were positively correlated with the prevalence in controls across the 11 sites of use of high-potency cannabis (r = 0·7; p=0·0286) and daily use (r = 0·8; p=0·0109).

INTERPRETATION:

Differences in frequency of daily cannabis use and in use of high-potency cannabis contributed to the striking variation in the incidence of psychotic disorder across the 11 studied sites. Given the increasing availability of high-potency cannabis, this has important implications for public health.

FUNDING SOURCE:

Medical Research Council, the European Community's Seventh Framework Program grant, São Paulo Research Foundation, National Institute for Health Research (NIHR) Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust and King's College London and the NIHR BRC at University College London, Wellcome Trust.

PMID:
30902669
DOI:
10.1016/S2215-0366(19)30048-3
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