Researchers have long wondered about the effect that marijuana can have on both sexual and reproductive health in men and women. Past studies, for instance, have shown that cannabis use can lower sperm counts and testosterone in men. Other research has found that, for women, smoking marijuana decreased levels of key hormones and caused irregularities in ovulation and menstruation.
Combine these two supposed reproductive system-inhibiting effects and you would think that couples who use marijuana would experience more difficulty getting pregnant than those without so much as a joint in the house. And yet researchers at Boston University School of Medicine recently found that couples who reported using cannabis had no more infertility issues than couples who did not. The study, published in the Journal of Epidemiology and Community Health, surveyed 4,194 women aged 21 to 45 living in the US or Canada, as well as 1,125 of their male partners. It is the first study, the researchers say, measuring the actual reproductive rate of marijuana users as they tried to conceive.
The 12 percent of female and 14 percent of male participants who said they got high were not at any increased risk of infertility, which surprised the study authors. “All background research points to this being a harmful mix,” says lead author Lauren A. Wise, a professor of epidemiology at Boston University School of Public Health. “We went into this thinking we would find something bad.”
The researchers sought out stable couples trying to conceive and enrolled them in Boston University’s pregnancy internet survey, PRESTO, at the time they ceased using birth control. (This was so the study wasn’t biased toward couples who were already having trouble getting pregnant). The study authors did not solicit explicitly for marijuana users, but knew they would inevitably find them in a large sample from the general population, identifying them in a vast questionnaire that also asked about body mass index, household income, caffeine use, and so on, to control for various factors. “They didn’t know anything about the hypothesis of the study,” Wise says.
Incidentally, they wound up with more cannabis users than identified in other US national averages—14 percent of men in their study compared to 12 percent of men in national surveys and 12 percent of women compared to a national average of 7 percent.
Ninety-five percent of couples in the survey did eventually conceive. That rate remained consistent, with no statistically significant variation among couples in which one or both partners used marijuana. Frequency of cannabis intake also did not impact the pregnancy rate.
Wise says the study will not be the last word on fertility rates and cannabis use, and thinks the research is further made important by the blitz of states legalizing weed in the US, which she says will inevitably increase use. She would like to measure the effects of using marijuana medicinally versus recreationally on the baby-making process.
As for now: “Our data was very consistent,” she says. “There was no association at all between marijuana use and fertility.”