Dirty Dozen Negative Outcomes of Adolescent Marijuana Use #8: Marijuana Decreases Fertility Rates

By Laura Stack

Decades ago, Big Tobacco realized their consumer base was steadily killing itself off due to illnesses caused by heavy tobacco use, particularly emphysema, heart disease, and cancers. The industry kept this to themselves, because the only way to maintain said consumer base was by recruiting more smokers as the others died, especially young people. So, they portrayed their product as hip, cool, and popular—and briefly, as actually healthy for users. It took a while for the populace at large to catch on, and for the government to take serious action to protect consumers.

As with so other many ways they’ve mimicked Big Tobacco, the rapidly-growing Big Marijuana may soon have to play the same deadly game with its users—except in the long run, prospects are far worse for the marijuana industry and its consumers. Not only does their product cause the same illnesses of inhaled smoke, it’s far nastier in that it can also cause other physical illnesses—including CHS, a condition that can literally make you vomit to death—and mental disorders as serious as psychosis and schizophrenia. Perhaps worse is something many users never consider—it can ensure they fail to reproduce.

Marijuana and Male Fertility

From a reproductive standpoint, marijuana affects men and women in different ways. We know daily marijuana use at ages 15-17 by people who later became mothers and fathers is associated with a sixfold increase in having babies born pre-term and with low birth weights. This result did not hold for marijuana use at other ages or for tobacco use at all. We also know that cannabinoids are an important cause of community-wide genotoxicity impacting both birth defect and cancer epidemiology at the chromosomal hundred-megabase level.

We know marijuana is bad for male fertility through a recently systematic literature review of medical databases on the subject. The authors noted “evidence of cannabis induced alterations in male fertility” in terms of “semen parameters.” Heavy users suffered lower sperm counts, lower sperm concentration, and higher levels of sperm abnormalities that reduced motility, viability, and fertilization capacity. Men who use marijuana once a week suffer as much as a 30% decrease in sperm count and concentration, which can last as long as six weeks after they stop using.

Male rats exposed to high levels of THC, marijuana’s active psychoactive ingredient, show reduced libido and sexual function, as well as a decrease in the hormones that encourage conception. The rats also display atrophy (shrinking) of the testicles. This last might be enough to discourage marijuana use among men, if the results were widely known. We don’t know whether the rat results would apply to humans, but scientists often use rats for such studies because, like humans, they’re extremely tough and adaptable, and are the closest thing to human that researchers can experiment on without resorting to primates. 

Marijuana in Female Fertility

Given the nature of the female reproductive system, it’s not as easy to tell how marijuana affects women. However, it’s becoming clearer that marijuana may impair female fertility. Marijuana may impair female fertility, says the title of a worrisome paper published in Science Daily in April 2020, based on an animal-model paper presented at the Endocrine Society’s 2020 annual meeting. In the past, many fertility specialists considered the evidence for a link between infertility and marijuana to be weak but recommended against cannabis use anyway—for good reason, as it turns out. Cow eggs exposed to high levels of THC had great difficulty reaching standard developmental milestones than unexposed eggs. The THC negatively affected at least 62 genes, resulting in poor-quality embryos that were more likely to be miscarried. Whether this applies to humans or not is difficult to determine at this time.

Meanwhile, a study involving 1,200 women trying to conceive, including 62 who had used marijuana during this period, showed female users were 41% less likely to conceive for each monthly cycle. Among the small user group, 42% got pregnant during the study period, as opposed to 66% of the non-users. According to the authors, animal studies indicate that high levels of THC in the bloodstream (and nearly all pot products have high levels of THC nowadays) can also damage the uterine lining, making fertilized eggs less likely to implant and develop. In a similar study of 326 women in Boston, those who had never used marijuana had double the pregnancy rate of the very small number of women who admitted to marijuana use (just 9) during the study period.

The bottom line

Recent research has shown that regular marijuana usage lowers fertility rates in both sexes and may also increase miscarriages in women. Anecdotal evidence, while not accepted as scientific, backs this up. In a recent conversation, a colleague of mine informed me that he knows of two couples trying to get pregnant who smoke marijuana regularly. In one of the couples, use is daily and heavy for both partners. The daily users have one child, from the woman’s previous marriage; it took 3.5 years for her to conceive that child. She and her current partner have been trying to have a child for two years now. The second couple remain childless after nearly six years of marriage. The woman smokes infrequently, but the man smokes daily and heavily. Both couples know about the fertility research, but either don’t believe in it or don’t care. It doesn’t stop them from smoking pot or even slow them down.

If the idea that couples may have to choose between marijuana and parenthood doesn’t give marijuana users pause, nothing will.

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