The study, conducted between early-2023 and mid-2024, involved men who had been diagnosed with either prostate cancer or a non-cancerous enlargement of the prostate, called benign prostatic hyperplasia. These two groups were chosen because both involve prostate-related issues, but only one involves cancer.

Over 2,500 patients were invited to complete a questionnaire about their past and present substance use, with a strong focus on cannabis. After carefully categorising respondents by age and eliminating incomplete surveys, the researchers ended up with 462 participants, evenly split between the two conditions.

About two-thirds of men in each group reported using cannabis, whether occasionally or frequently. They also reported similar consumption habits – such as smoking, vaping, or eating edibles – as well as the type of cannabis they used, including THC-dominant, CBD-dominant, or balanced products.

When Dr Rosewall and her colleagues analysed the data, they found something surprising: there was no significant difference in cannabis use between those with prostate cancer and those with benign prostatic hyperplasia.

Even when the researchers performed deeper analysis – by investigating what age the men started using cannabis or how long they had used it overall – they found no meaningful differences between the cancer and non-cancer groups. Statistical modelling confirmed that neither infrequent nor frequent cannabis use appeared to have any impact on the likelihood of developing prostate cancer.

The team’s results challenge many assumptions that people may have about cannabis and cancer risk. While lab studies have suggested that cannabis compounds might have an effect on prostate cells, this real-world study in humans found no evidence of harm – or any benefit – when it comes to developing prostate cancer.

With arms-length funding from the Ontario Cannabis Store’s Social Impact Fund, this study is part of a growing effort to better understand the health implications of cannabis in the era of legalization in Canada. Further research will help to achieve a more complete picture of cannabis and men’s health.