Marijuana and Fertility: what we know, what we don’t know, and what this may mean for you
Recently, I’ve been asked a few times about the effects of marijuana use on fertility - particularly its effect on male fertility. While this is new territory for me, it isn’t surprising that the question is coming up. Medicinal and recreational use of marijuana is becoming more mainstream with recreational use legal in 11 states and medical use allowed in 20 more. And, marijuanna use is highest in men of reproductive age.
So, naturally, these questions prompted me to dig into the literature. Today, I’m sharing a (very abridged) summary of what I learned.
Background
THC is the main active compound in marijuana that produces its psychoactive effects (i.e. the high). It does so by interacting with the endocannabinoid system - a set of molecules and receptors found widely throughout our bodies that help regulate many basic bodily functions. Specifically, THC interacts with the CB1 and CB2 receptors. These receptors are found throughout our brains - including in a part of the brain that regulates egg and sperm development - as well as in the testis, vas deferens, and sperm of men and ovaries and uterus of women (1, 2). Therefore, it seems likely that marijuana use can affect fertility.
Studies in animals suggest that this is true. For example, THC has been shown to decrease luteinizing hormone, which is important in sperm development, in male mice and monkeys and long term exposure to THC causes hypogonadism (shrinkage of the testes) in mice and rats. Experiments on human sperm have shown that activation of the CB1 and CB2 receptors decreases their motility, viability, and ability to penetrate an egg. Experiments in female monkeys showed that injections of THC in the first half of the menstrual cycle caused longer, anovulatory cycles. In vitro studies on human embryos suggest that THC exposure may negatively affect the ability of the embryo to implant in the uterus (1, 2).
However, research in humans is limited. There are obvious ethical barriers to randomized controlled trials (the gold standard of clinical research) in this space. And, the few observational studies available struggle with the accuracy of self reported marijuana use. Finally, extrapolating from animal studies to humans is challenging because these effects likely depend on the amount and frequency of marijuana use (i.e. most humans probably don’t use marijuana the way lab rats do - fixed amounts on a schedule).
What we do know
But, we do know some things. In men, the evidence for the effect of marijuana on semen parameters is strongest. Studies in animals and humans show that marijuana use reduces sperm count, concentration, morphology, motility, viability, and fertilization ability (3). Data on effects in women are less clear. However, marijuana use during pregnancy is associated with increased rates of preterm birth and babies that are small for gestational age. And, animal studies and a few small studies in humans suggest that marijuana use may also affect ovulation and embryo implantation (2).
So, what do I do with this information?
First, be honest with your doctor about your marijuana use. Your fertility doctor is in the business of helping you build your family not of judging your lifestyle choices. This information may help them help you better. (That said, if you do feel judged or discriminated against by your doctor - which is different than disagreeing with their recommendation - you may want to look for a better fit.)
Second, whether you are a man or a woman, if you use marijuana, consider cutting back or stopping while you are trying to conceive. There is a lot we don’t yet know about the effects of marijuana on fertility. But, there is compelling evidence that it can have a negative effect. Of course, I realize that this may be easier said than done. If you are using marijuana for medicinal purposes, you will likely want to have a conversation with your prescribing doctor and your fertility doctor about the risks and benefits of other options for symptom management. If you or your partner struggle with controlling recreational use, have an open, non-judgmental conversation about how this may be affecting your ability to build a family together and seek help. Treatments such as cognitive behavioral therapy, motivational enhancement therapy, and contingency management have been shown to be beneficial (4). Your doctor can help you find appropriate treatment for you.
And what about CBD?
This is a great question. I really couldn’t find much literature on this. CBD doesn’t directly activate either the CB1 or CB2 receptors but rather modifies how they function. So, it stands to reason that CBD may also affect fertility but what those effects are is currently unclear.
Please note: this article provides a synthesis of information and perspective and should not be taken as medical advice. Please discuss all concerns and treatment decisions with your physician.
Citations:
Plessis SS, Agarwal A, Syriac A. Marijuana, phytocannabinoids, the endocannabinoid system, and male fertility. J Assisted Reprod Genet 2015; 32:1575-1588.
Brents LK. Marijuana, the endocannabinoid system, and the female reproductive system. YJBM 2016; 89: 175-191.
Payne KS, Mazur DJ, Hotaling JM, Pastuszak AW. Cannabis and Male Fertility: A Systematic Review. J Urol. 2019; 202(4): 674-681. doi:10.1097/JU.0000000000000248
Sherman B, McRae‐Clark AL. Treatment of Cannabis Use Disorder: Current Science and Future Outlook. Pharmacotherapy, 2016; 36: 511-535. doi:10.1002/phar.1747