No increase in cannabis-induced psychosis after legalization: evidence from 17 months of data in Canada

cannabis-induced psychosis

Cannabis-induced psychosis: A myth or a reality? A new study from Canada sheds light on the issue

One of the common arguments against cannabis legalization is that it would lead to a surge of cannabis-induced psychosis among the population. The fear is that the modern strains of cannabis are too potent and can trigger cannabis-induced psychosis in vulnerable individuals. But is there any evidence to support this claim? A new study from Canada suggests otherwise.

The study, conducted by a team of 14 researchers led by Dr. Kelly Anderson, principal investigator for the Canadian Institutes of Health Research’s Project Grant from 2021–2022, examined the impact of non-medical cannabis legalization on health service use and incident cases of cannabis-induced psychosis in Ontario, Canada. The study, titled Impact of Non-medical Cannabis Legalization With Market Restrictions on Health Service Use and Incident Cases of Psychotic Disorder in Ontario, Canada, was published in the journal Schizophrenia Research.

The researchers analyzed data from Ontario, the most populous province in Canada, from January 2014 to March 2020. This period covered both the pre- and post-legalization phases, as Canada legalized recreational cannabis in October 2018. The researchers looked at various indicators of cannabis-induced psychosis-related health service use, such as outpatient visits, emergency department visits, hospitalizations, and inpatient length of stay, as well as incident cases of cannabis-induced psychosis. They focused on the age group of 14 to 60 years, which is the most likely to use cannabis and develop cannabis-induced psychosis.

The results showed that there was no evidence of any increase in health service use or incident cases of cannabis-induced psychosis in the 17 months following cannabis legalization in Canada. The researchers did observe an increasing trend in substance-induced psychotic disorders over the entire study period, but they did not find any specific association with cannabis use.

The researchers also did not find any evidence of differences in the rates of cannabis-induced psychosis across different socio-demographic groups, such as gender, age, income, or urban/rural location, before and after legalization. This suggests that cannabis legalization did not have a differential impact on key population subgroups.

The researchers concluded that their findings do not support the hypothesis that non-medical cannabis legalization in Canada had population-level impacts on cannabis-induced psychosis. However, they also cautioned that their study had some limitations, such as the short post-legalization observation period, the tight restrictions on retail stores and product types, and the lack of data on cannabis consumption and potency. They recommended that a longer and more comprehensive study is needed to fully understand the effects of cannabis legalization on cannabis-induced psychosis.

The study has important implications for the ongoing debate on cannabis legalization, especially in the U.S., where the federal government still classifies cannabis as a Schedule I drug with no medical value and high potential for abuse. The study challenges the notion that cannabis legalization would lead to mass hysteria and cannabis-induced psychosis among the public, as some opponents of legalization claim. The study also shows that cannabis legalization can be implemented in a responsible and regulated manner, without compromising public health and safety.

This study is not a random term paper, but a rigorous and peer-reviewed research project led by one of Canada’s top public health sector academics. Dr. Kelly Anderson is an associate professor in the Department of Epidemiology and Biostatistics at Western University and a scientist at the Institute for Clinical Evaluative Sciences. She has extensive experience and expertise in mental health services research and health policy analysis.

The study is also not an isolated case, but part of a growing body of evidence that supports the benefits of cannabis legalization. For example, a recent study from the U.S. found that cannabis legalization was associated with a reduction in opioid-related deaths, while another from Canada found that cannabis legalization was associated with a decrease in alcohol consumption. These studies suggest that cannabis legalization may have positive impacts on public health, beyond the value of cannabis for medical conditions.


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