Key findings released from study exploring impacts of cannabis legalization

Share this:

Last year, HRI received $100,000 in funding from the Canadian Centre on Substance Use and Addiction (CCSA) and Health Canada to study the effects of cannabis legalization on at-risk populations. Findings from this project are now available.

Photo of a cannabis plant.

HRI’s Director of Research and Evaluation, Dr. Jean Costello, led the study, which utilized patient data from Homewood Health Centre and St. Joseph’s Healthcare Hamilton. The study was co-led by HRI Senior Scientist, Dr. James MacKillop, and involved collaboration with other researchers at the Peter Boris Centre for Addictions Research in Hamilton, Ontario.

Together, the team examined the effects of cannabis legalization among sub-populations who already use cannabis at elevated rates, including people receiving treatment for substance use disorder (SUD) and concurrent disorders.

Key findings from the study include:

  1. Legalization of non-medical cannabis, at least in this early stage, has not led to substantive increases in cannabis use or cannabis use disorder (CUD) symptom severity, nor has it led to a decrease in readiness to quit in two samples of individuals with SUD.
  2. Similarly, there were no significant changes pre- and post-legalization in the prevalence of tobacco, alcohol, or other drug use within these two samples.
  3. Elevated CUD symptom severity was associated with more severe symptoms of PTSD, anxiety, and depression.

Notably, the team identified discrete profiles representing varying degrees of CUD and psychiatric symptom severity within these two samples and found significant differences between the profiles in age, sex, and other substance use characteristics.

These findings address an important gap by providing insight into the early effects of legalization on individuals with SUD. The study also highlights the importance of considering CUD and psychiatric comorbidities in future cannabis policy and monitoring efforts.

In June 2022, CCSA issued a Policy Brief that incorporates findings from this and other studies aimed at shedding light on the early impacts of cannabis legalization. The Brief will inform those involved in advising or studying cannabis regulation and serve as a resource to those completing mandatory reviews of the Cannabis Act in Canada.