Background: The Cannabis Act (Bill C-45) was enacted in 2018, to legalize and regulate the use, production, and sale of nonmedical cannabis in Canada. While public health and safety implications of cannabis legalization have yet to be elucidated, the wide availability of cannabis necessitates health care providers to be knowledgeable about therapeutic potential and side effects of use. This study aimed to examine the temporal trends over two decades and the impact of the Cannabis Act in Canada, implemented in October 2018, on substance use, semen parameters, and testosterone levels of infertile men.

Methods: We conducted a retrospective cohort study from a prospectively maintained database of a single infertility clinic. Demographic, fertility, and substance use history were correlated with semen and hormone assessments. Temporal trends in cannabis use and semen quality between 2001 and 2021 were investigated and compared between pre-cannabis legalization eras (PRCL) and post-cannabis legalization eras (POCL).

Results: Our cohort included 11,630 patients (9411 PRCL and 2230 POCL). Cannabis use increased by 8.4% per year (p<0.001), while alcohol and tobacco consumption declined (0.8% and 1.5% per year, p<0.05 and p=0.004, respectively). Similar trends were noticed in the POCL, with higher rates of cannabis use (22.4% vs. 12.9%, p<0.001) and decreased tobacco and alcohol intake (15.2% vs. 17.7%, p=0.005 and 50.5% vs. 55.2%, p<0.001, respectively) compared to the PRCL group. Semen concentration was lower in the POCL group (24.8±44.8 vs. 28.7±48.3 million/mL, p=0.03). Testosterone did not differ between the cohorts. Comparison between cannabis users (n=1715) and nonusers (n=9924) demonstrated a slight increase in sperm motility (25.9%±15.3% vs. 23.9%±15.0%, p=0.002) and decreased sperm concentration among users (27.6±53.5 vs. 23.9±15.0 million/mL, p=0.03).

Conclusion: A nearly 10% rise in cannabis use in the POCL era was observed among men being investigated for infertility. Our data suggest cannabis use may be associated with an increase in testosterone, slightly improved sperm motility, and decreased sperm concentration.