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Curr Psychiatry Rep. 2016 Feb;18(2):12. doi: 10.1007/s11920-015-0657-y.

Cannabis and Psychosis: a Critical Overview of the Relationship.

Ksir C1, Hart CL2,3,4,5.

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Department of Psychology and Neuroscience Program, University of Wyoming, Laramie, WY, USA.
Division on Substance Abuse, New York State Psychiatric Institute, Columbia University, 1051 Riverside Dr., Unit 120, New York, NY, 10032, USA.
Department of Psychology, Columbia College, 1190 Amsterdam Ave, Schermerhorn #406, New York, NY, 10027, USA.
Department of Psychiatry, Columbia University, 1051 Riverside Dr., Unit 120, New York, NY, 10032, USA.
Brocher Foundation, Geneva, Switzerland.


Interest in the relationship between cannabis use and psychosis has increased dramatically in recent years, in part because of concerns related to the growing availability of cannabis and potential risks to health and human functioning. There now exists a plethora of scientific articles addressing this issue, but few provide a clear verdict about the causal nature of the cannabis-psychosis association. Here, we review recent research reports on cannabis and psychosis, giving particular attention to how each report provides evidence relating to two hypotheses: (1) cannabis as a contributing cause and (2) shared vulnerability. Two primary kinds of data are brought to bear on this issue: studies done with schizophrenic patients and studies of first-episode psychosis. Evidence reviewed here suggests that cannabis does not in itself cause a psychosis disorder. Rather, the evidence leads us to conclude that both early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis. The role of early and heavy cannabis use as a prodromal sign merits further examination, along with a variety of other problem behaviors (e.g., early or heavy use of cigarettes or alcohol and poor school performance). Future research studies that focus exclusively on the cannabis-psychosis association will therefore be of little value in our quest to better understand psychosis and how and why it occurs.


Cognition; Marijuana; Mental illness; Psychotic disorder; Schizophrenia; THC

[Indexed for MEDLINE]

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