Study: No Significant Association Between Cannabis Use, Developing Psychosis

Scientists have explored the potential link between cannabis and psychosis for years now.

While experts have argued in the past that the link between psychosis and cannabis is overstated, another study published just last year linked increased risk of psychosis and addiction to high-potency cannabis.

Now, a new study published in the journal Psychiatry and Clinical Neurosciences is sharing another perspective, finding that cannabis use is not associated with an increased risk of developing psychosis, even among those predisposed to the disorder. 

The research was conducted by a team of investigators from Australia, Europe and the United Kingdom.

Exploring Psychosis and Cannabis

The authors point to the history of research on this specific issue, adding that there have been “limited prospective studies” on the topic and that “the direction of this association remains controversial.”

They describe the study’s primary aim, “to examine the association between cannabis use and the incidence of psychotic disorders in people at clinical high risk of psychosis.” Researchers were also looking to assess associations between “cannabis use and the persistence of psychotic symptoms, and with functional outcome.”

For this study, researchers assessed the relationship between cannabis use and the incidence of psychotic disorders in clinically at-risk subjects. The study analyzed 334 individuals who are at high risk of developing psychosis, along with 67 healthy control subjects at baseline. The investigators then followed up on the participants over a two-year period using a modified version of the Cannabis Experience Questionnaire.

During the follow up, 16.2% of the clinical high-risk sample developed psychosis. Of those who did not develop psychosis, 51.4% had persistent symptoms and 48.6% were in remission. 

Authors ultimately stated, “There was no significant association between any measure of cannabis use at baseline and either transition to psychosis, the persistence of symptoms, or functional outcome.” They added that the findings “contrast with epidemiological data that suggest that cannabis use increases the risk of psychotic disorder.”

A Potentially Misunderstood Topic

The findings are indeed contrary to a number of other recent studies on cannabis and psychosis, though there may be more to this conversation than initially meets the eye. 

A 2016 review of previous research published by The Lancet (the journal which also published the 2022 study) found that people already experiencing psychosis can improve outcomes by reducing or eliminating cannabis use. This essentially shows that cannabis does not exhibit a causal relationship to psychosis. 

While people with psychotic illnesses may use cannabis and other substances more often, studies showing lifetime incidences of acute cannabis-induced psychosis in the general population are still rare.

This study specifically showed that, even among those predisposed to psychosis, a history of cannabis use is not associated with an increased risk of developing the illness. While authors noted that further research is still needed to understand the relationship between cannabis use and mental health outcomes, these findings could help to shift perspectives on policy and healthcare in the future.

Affirming Previous Findings

It’s also not the only study to come to a similar conclusion. 

A 2022 study published in the Canadian Journal of Psychiatry analyzed emergency room data related to cannabis-induced psychosis. Researchers concluded that the implementation of Canada’s cannabis legalization program “was not associated with evidence of significant changes in cannabis-induced psychosis or schizophrenia ED presentations.”

A similar study, published in January 2023 in the Journal of the American Medical Association, looked at the same question in relation to the United States, analyzing data from 2003 to 2017. Researchers came to the same conclusion, “The findings of this study do not support an association between state policies legalizing cannabis and psychosis-related outcomes.”

  1. Astounding to see good quality and positive cannabis research come out of the UK, a country where drug researchers frequently seem stuck in the 1990s and have only heard of “skunk” cultivars.

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