If cannabis caused schizophrenia--how many cannabis users may need to be prevented in order to prevent one case of schizophrenia? England and Wales calculations
Abstract
BACKGROUND: We consider how many cannabis users may need to be prevented in order to prevent one case of schizophrenia or psychosis [defined as number needed to prevent (NNP)]. METHOD: Calculation for England and Wales using best available estimates of: incidence of schizophrenia; rates of heavy and light cannabis use; and risk that cannabis causes schizophrenia. RESULTS: In men the annual mean NNP for heavy cannabis and schizophrenia ranged from 2800 [90% confidence interval (CI) 2018-4530] in those aged 20-24 years to 4700 (90% CI 3114-8416) in those aged 35-39. In women, mean NNP for heavy cannabis use and schizophrenia ranged from 5470 (90% CI 3640-9839) in those aged 25-29 to 10 870 (90% CI 6786-22 732) in 35-39-year-olds. Equivalent mean NNP for heavy cannabis use and psychosis were lower, from 1360 (90% CI 1007-2124) in men aged 20-24 and 2480 (90% CI 1408-3518) in women aged 16-19. The mean and median number of light cannabis users that would need to be prevented in order to prevent one case of schizophrenia or psychosis per year are four to five times greater than among heavy users. CONCLUSIONS: The number of young people who need to be exposed to an intervention to generate NNP and prevent one case of schizophrenia will be even larger. The public health importance of preventing cannabis to reduce schizophrenia or psychosis remains uncertain. More attention should be given to testing the hypothesis that cannabis is related causally to psychotic outcomes, and to considering what strategies will be the most effective in reducing heavy cannabis use among young people.
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Current treatments for cannabis dependence have approximately 20% efficacy.
“Given that current treatments for cannabis dependence have approximately 20% efficacy (68)”
From Association Between Cannabis and Psychosis: Epidemiologic Evidence (2016) · cites this paper as [68]
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- Authors
- Hickman, M., Vickerman, P., Macleod, J., Lewis, G., Zammit, S., Kirkbride, J., & Jones, P.
- Affiliations
- University of Bristol (GB)
- University of Cambridge (GB)
- Venue
- Addiction
- Publisher
- Wiley
- Published
- 2009-10-09
- Volume
- 104
- Issue
- 11
- Pages
- 1856-1861
- ISSN
- 0965-2140 (ISSN-L)
- 1360-0443
- OpenAlex
- W1990938045
- Cited by
- 58
- References
- 21
- Citations by year
- 2023: 1 · 2022: 3 · 2021: 2 · 2020: 1 · 2018: 2 · 2017: 1 · 2016: 6 · 2015: 10 · 2014: 10 · 2013: 5 · 2012: 5
- FWCI
- 4.03
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Addiction (publishedVersion)
- PubMed (publishedVersion)
- UCL Discovery (University College London) (submittedVersion)
- Bristol Research (University of Bristol) (submittedVersion)
- Funders
- World Health Organization
- Economic and Social Research Council (ES/G007543/1)
- Topics
- Health Sciences › Medicine › Pharmacology › Cannabis and Cannabinoid Research
- Health Sciences › Medicine › Psychiatry and Mental health › Schizophrenia research and treatment
- Health Sciences › Medicine › Epidemiology › Substance Abuse Treatment and Outcomes
- Keywords
- cannabis use, schizophrenia, psychosis, heavy cannabis use, cannabis-related psychosis, youth, public health prevention
- MeSH terms
- Adolescent, Adult, Marijuana Abuse, Epidemiologic Methods, Female, United Kingdom, Humans, Male, Psychoses, Substance-Induced, Research Design, Schizophrenia, Sex Factors, Young Adult
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