Chronic marijuana use can greatly affect male fertility and reproductive outcomes, according to a new report published in the journal Fertility & Sterility. This is the first study that evaluates the impact of substance use on testicular function using a mode of delivery and dosage that reflects a person's current intake.
Scientists at the Oregon National Primate Research Center at the Oregon Health and Science University observed the reproductive system of healthy male non-human primates after THC.
Non-human primates of reproductive age with proven paternity and no previous cannabis use received edible THC once daily for seven months. Their THC dose was based on published guidelines for medical marijuana acclimatization for humans and increased every 70 days to match the animal's sperm development cycle. The dose was adjusted until it reached the human equivalent of a heavy dose of cannabis. Semen samples were collected at baseline before starting THC and at the end of each THC dosing time point.
“Our analysis of collected samples showed that THC consumption was associated with significant adverse effects on animal reproductive hormones, including decreased testosterone levels and severe testicular shrinkage. Specifically, we observed a reduction in testicular size of more than 50%,” said study senior author Jamie Lo, MD.
While more research is needed to better understand the potential long-term effects of THC in humans, these early results are clinically troubling. As the prevalence of cannabis use continues to rise in the US and worldwide, especially among men of reproductive age, even modest doses can have a serious impact on fertility outcomes. The long-term effects of THC on male reproductive health are not clearly defined, but according to the researchers, it is possible that THC could cause long-term effects that could change family planning.
Researchers will continue to expand their understanding of the relationship between THC and the reproductive health of both male and female non-human primates. The research team will study the long-term effects of THC exposure, including changes in sperm count and motility, and the possibility of eliminating side effects when THC products are discontinued.