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Cannabis-Induced Psychosis: A Review: Page 5 of 5

Cannabis-Induced Psychosis: A Review: Page 5 of 5

© Elisa Manzati/shutterstock.com© Elisa Manzati/shutterstock.com
A comparison of clinical features of idiopathic vs cannabis-induced psychosisTABLE. A comparison of the clinical features of idiopathic versus cann...
Treatment of cannabis-induced psychosisFigure. Treatment of cannabis-induced psychosis

Carbamazepine has also been shown to have rapid effects when used as an adjunct to antipsychotics.11 Use of anti-seizure medication in CIP treatment has been hypothesized to reduce neuroleptic adverse effects, resulting in better tolerance of antipsychotics.10,11 These results suggest the use of adjunctive antiepileptics should be considered in CIP treatment strategies, although further studies in a broad range of patients with CIP are needed.

Abstaining from cannabis is the most beneficial and effective measure for preventing future CIP events; however, it is likely to be the most difficult to implement. Psychosocial intervention has a significant impact on early-phase psychosis, and when the intervention is initiated plays a role in disease outcomes. A delay in providing intensive psychosocial treatment has been associated with more negative symptoms compared with a delay in administrating antipsychotic medication.12 Employing cannabis- focused interventions with dependent patients who present with first-episode psychosis can decrease use in a clinically meaningful way and subjectively improve patient quality of life.

Compared with the standard of care, motivational interviewing significantly increases number of days abstinent from cannabis and aids in decreasing short-term consumption.13 Patients who are treated with motivational interviewing in addition to standard of care (combination of antipsychotic medication, regular office-based psychiatric contact, psychoeducation) are reported to also have more confidence and willingness to reduce cannabis use.

Patients with CIP who are unwilling or unable to decrease cannabis consumption may be protected from psychotic relapse with aripiprazole (10 mg/d). Its use suppresses the reemergence of psychosis without altering cannabis levels. However, no direct comparison has been made with aripiprazole and other antipsychotics in treating CIP. Clearly, well-controlled large studies of putative treatments for CIP are needed.


As more countries and states approve legalization, and marijuana becomes more accessible, CIP and other cannabis-related disorders are expected to increase. Efforts should be made by physicians to educate patients and discourage cannabis use. Just as there was an era of ignorance concerning the damaging effects of tobacco, today’s conceptions about cannabis may in fact be judged similarly in the future. The onus is on psychiatrists to take an evidence-based approach to this increasing problem.



Dr. Grewal is a recent MD graduate of Avalon University School of Medicine in Willemstad, Curaçao. Dr. George is Chief of Addictions at the Centre for Addiction and Mental Health (CAMH) and Professor and Director of the Division of Brain and Therapeutics in the Department of Psychiatry at the University of Toronto. Dr. George’s research is supported by the Canadian Institutes of Health Research (CIHR), the CAMH Foundation, and the National Institute on Drug Abuse (NIDA).

Dr. Grewal reports no conflict of interest concerning the subject matter of this article. Dr. George reports that he is a consultant to Novartis, the American College of Neuro­psychology, and the Canadian Center for Substance Use and Addiction.


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