Rationale: Cannabis use among young adults is on the rise; about 42% report using cannabis in 2023. Along with this, evidence of potential harm is also rising. This study investigated intergenerational risks to future children, passed from fathers.

Method: Sperm was collected from 24 men aged 18-40: 12 were consistent users and 12 were non-users. Researchers evaluated the concentration of sperm, genetic changes, and other indicators of sperm health and quality. The researchers conducted a parallel controlled experiment using rats to see if effects of cannabis generalized to another species.

Results: The concentration of sperm in samples from cannabis users was about 40% lower than in non-users. Sperm from human cannabis users, as well as rats given THC, had a host of genetic alterations. For example, the genome of sperm from human cannabis users showed more than 6500 structural alterations, many of which were replicated in THC-exposed rats.

Meaning:  These results indicate potential epigenetic effects of cannabis exposure due to THC. Changes in legal status and use patterns have increased the prevalence of use among males of child-bearing potential. The risks of exposure are likely to be retained in their embryos and may compromise the health and wellbeing of their future offspring. These findings have implications for cannabis use policy.