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Chronic marijuana use alters female reproductive system, may impact successful conception

OHSU study finds association between THC, ovulatory disfunction in nonhuman primates
Hands in blue nitrile gloves hold tweezers to transfer medical marijuana buds to a petri dish; several Erlenmeyer flasks with liquid in them are seen in the background and foreground.
An OHSU study in nonhuman primates finds that regular use of marijuana products may increase risks of ovulatory disfunction. (Getty Images)

The use of marijuana products as often as three times per week may have profound impacts on menstrual cycles and female reproductive hormones, says a new report published online in the journal Fertility & Sterility Science.

The study, conducted at the Oregon National Primate Research Center at Oregon Health & Science University, monitored the reproductive systems of healthy female nonhuman primates following exposure to Delta-9-tetrahydrocannabinol, or THC, the main psychoactive ingredient in marijuana.

The nonhuman primates, all of reproductive age with a history of successful conception, received a THC edible once daily over the course of three months. The edible was ingested in addition to their standard diet of chow. THC dosing, based on published medical marijuana acclimation recommendations for humans, increased monthly with the largest dose reaching 2.5mg.

Close-in head shot of Jamie Lo, M.D., a smiling Asian woman with long, black hair
Jamie Lo, M.D.

“In just a short time period, we observed irregularity in the animals’ reproductive cycles,” said the study’s lead author Jamie Lo, M.D., MCR, associate professor of obstetrics and gynecology (perinatology and maternal-fetal medicine), OHSU School of Medicine, and Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center. “Overall, menstrual periods were longer in duration and levels of follicle stimulating hormone, one of the critical regulators for the body’s reproductive function, increased. These factors suggest the strong potential for reproductive system dysfunction that, in turn, may impact the ability to become pregnant.”

Not surprisingly, notes Lo, as the dose of THC increased, so did the impact to menstrual cycle length and follicle stimulating hormone levels. “While we don’t yet know why THC influences the female reproductive system, we do know that the response appears to be dose dependent. This means that the higher concentration of THC that is being used, the more the reproductive system is affected,” she says.

Recent data show that the most significant increases in THC use are among people 18 to 29 years old. While more research is necessary to understand the long-term effects that chronic marijuana use may have on the reproductive system, Lo suggests that patients and their health care providers consider the potential impacts.

“While starting a family may not seem like a priority in your early 20s, the downstream repercussions of regular marijuana use may indeed hamper longer term plans,” she says.

Additionally, Lo and colleagues within the OHSU Department of Urology, and at Harvard Medical School, Boston University and the University of Colorado, are using a similar study model to determine the result of chronic THC use on sperm production in male nonhuman primates. Study findings are expected in 2022.

This research is supported by National Institutes of Health grants awarded through the Reproductive Scientist Development Program (K12 HD000849), Eunice Kennedy Shriver National Institute of Child Health and Human Development (R03 HD097116), and the Office of Research Infrastructure Program (P51 OD011092), as well as with the support of the March of Dimes Foundation and a Faculty Excellence and Innovation Award provided to Dr. Lo by the Silver Family Innovation Fund.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

This study was reviewed and approved by the OHSU Institutional Animal Care and Use Committee.

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