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Chapter 17 - Does Cannabis Cause Psychosis?

The Epidemiological Evidence

from Part VI - Cannabinoids and Schizophrenia: Aetiopathology and Treatment Implications

Published online by Cambridge University Press:  12 May 2023

Deepak Cyril D'Souza
Staff Psychiatrist, VA Connecticut Healthcare System; Professor of Psychiatry, Yale University School of Medicine
David Castle
University of Tasmania, Australia
Sir Robin Murray
Honorary Consultant Psychiatrist, Psychosis Service at the South London and Maudsley NHS Trust; Professor of Psychiatric Research at the Institute of Psychiatry
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In this chapter, we discuss whether there is a causal relationship between cannabis use and psychosis in terms of the criteria of causality proposed by Bradford-Hill. We conclude that the evidence for each of the criteria ranges from consistent in the context of strength, consistency, and temporality; strong in the context of biological gradient and experimental evidence; plausible in the context of biological plausibility and coherence. The association is not specific for psychosis but also includes depression and suicidal thoughts, and it is unclear whether the analogy criteira are appropriate. Thus, the epidemiological, experimental, and genetic evidence suggests that cannabis, particularly high potency cannabis, is a contributing factor to the incidence of psychosis in the population. In consequence, over the last 20 years there has been a shift in the argument from ‘whether there is a causal relationship between cannabis and psychosis’ to considering the magnitude of this relationship.

Marijuana and Madness , pp. 167 - 177
Publisher: Cambridge University Press
Print publication year: 2023

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