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Study Finds No Statistically Significant Difference in Rates of Psychosis-Related Diagnoses with Cannabis Legalization

Researchers from the Hospital of the University of Pennsylvania in Philadelphia and CU Boulder have conducted a study to examine the effects of state-level cannabis legalization on rates of psychosis-related diagnoses and prescribed antipsychotics. The study, which examined commercial and Medicare Advantage claims data from 2003 to 2017, found no statistically significant difference in the rates of psychosis-related diagnoses or prescribed antipsychotics in states with recreational or medical cannabis policies compared to states with no cannabis policy.[0]

The data used in the study was collected from the Institute for Behavioral Genetics and the Minnesota Center for Twin Family Research.[1] The study followed 4,000 twins, aged 24 to 49, since adolescence and collected data on the use of alcohol, tobacco, cannabis, and several illicit drugs, as well as measures of “psychosocial health.”[2] The measures for the study’s main outcome included sleep disturbance prevalence, self-reported sleep quality, sleep architecture, and sleep electroencephalography oscillations.[3]

The study also found no link between cannabis legalization and cognitive, psychological, social, relationship and financial problems.[1] The results of the study suggest that everyday adult use in a legalized environment should not be overly concerning.[2]

In secondary analyses, it was discovered that among men, people aged 55-64, and those of Asian heritage, the rate of psychosis-related diagnoses was higher in states with recreational policies than those without.[0] This suggests that certain populations that are predisposed to psychosis may be more vulnerable than others to experiencing negative impacts from cannabis use.

Another recent AMA-published study found that state-level medical marijuana legalization is associated with a significant decrease in opioid prescriptions and use among certain cancer patients.[4] This co-twin design controls for a wide range of variables and if the association holds up, it provides strong evidence that the environment, in this case legalization, is having an impact.[2]

In light of the new cannabis policies being adopted by states, the potential for psychosis to result from state cannabis legalization warrants further examination. It is important to take into consideration that no drug is risk-free and higher doses of a drug that is relatively safe in small amounts may cause harm.[2]

0. “Cannabis policy and psychosis – study finds no increase in rates of diagnosis” Cannabis Health News, 26 Jan. 2023,

1. “Legal cannabis not a ‘gateway drug’, research finds”, 26 Jan. 2023,

2. “Legalizing Cannabis May Reduce Alcohol Disorders: No Increase in Substance Abuse” Mirage News, 27 Jan. 2023,

3. “New Data Reveal Sleep Disturbance Affects Patients at All Stages of Psychosis” MD Magazine, 24 Jan. 2023,

4. “Marijuana Legalization Not Associated With Increased Rates Of Psychosis, American Medical Association Study Of 63 …” Marijuana Moment, 26 Jan. 2023,

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