Johnny Singh* had heard that smoking pot could affect his fertility, but he never considered quitting. He had been a daily user of medical and recreational marijuana for years before he and his wife conceived their first child when they weren’t even planning to start a family. “I heard pot brings your sperm count down, but that obviously wasn’t a problem for me,” he says between puffs of a joint. The couple had two more children—also surprise pregnancies—and they’re not alone in discovering that their fertility is seemingly unhindered by getting high.
Indeed, a new study has found that marijuana use by men or women does not, in fact, lower a couple’s chances of getting pregnant. While previous research has suggested that toking negatively affects how sperm behave, the Boston University study is the first to look specifically at the link between pot use and the likelihood of conceiving—and it found there isn’t one.
The researchers surveyed 4,194 women between the ages of 21 and 45 living in Canada or the United States about their marijuana use as part of a larger project examining the influence of lifestyle factors on fertility and pregnancy. The women were not using birth control or receiving fertility treatments and were in stable relationships with male partners. Those men were also invited to participate in the study, and 1,125 joined.
About 12 percent of women and 14 percent of men reported marijuana use in the two months before the initial survey—which, by the way, is not too far off the national rate of pot use. According to Health Canada, the number of Canadian men getting stoned has stayed steady in the past few years at about 15 percent, while the number of women has gone up from seven percent in 2013 to 10 percent in 2015.
“Given the increasing prevalence of marijuana use in Canada...and the scarcity of information on its health effects, we thought it would be a good time to investigate its effect on fertility,” says Lauren Wise, a professor of epidemiology at Boston University and lead author of the study, which was published last month in the Journal of Epidemiology and Community Health.
For the couples in the study, the probability of getting pregnant after 12 menstrual cycles was similar among those who used marijuana to those who did not.
The study controlled for a number of variables believed to affect a couple’s chances of conceiving, including frequency of intercourse, which was shown to be higher among marijuana users in this study and others. (So much for the cliché that pot makes you veg out and fall asleep!)
Wise says some human studies have shown marijuana has adverse effects on reproductive hormones, ovulation and semen quality, while others have not. Some research even indicates that people may build up a tolerance to the negative reproductive effects of pot over time. While studies about stoned sperm swimming in circles have stolen headlines, “Semen quality is just one determinant of a couple’s fertility,” Wise says.
For medical users like Singh, the study is welcome news. People who rely on drugs to treat medical conditions face the difficult decision of whether or not to continue their medication when trying to get pregnant. A better understanding of the effects of drugs on fertility can help them make more informed choices.
Still, if you're trying to get pregnant and have been avoiding cannabis, don’t spark a joint just yet. “I don’t think it’s wise to give any preconception advice based on the results of one just study,” says Wise. “More research is needed to see whether a consistent finding of no effect emerges from other studies of marijuana use and fertility.”
Future studies could look at whether dose, mode of ingestion and frequency and timing of use make a difference to fertility, she says.
How marijuana affects a developing baby is also uncertain, though some studies suggest pot use impairs growth and neurological development. Until more information is available, women may want to avoid marijuana during pregnancy, or discuss any medical needs for the drug with their doctor.
*Name has been changed.