Researchers have made a profound discovery in the field of cannabis science: even sperm can get high. A new study from Duke University indicates that heavy marijuana use in men can change the genetic makeup of their sperm, and might even alter genes which are passed on to their children.
A small study of just 24 participants recently found, for the first time, that higher concentrations of tetrahydrocannabinol (THC) in urine corresponded to a lower sperm count. The study also concluded that pot smokers had changes in the genetic profile of their sperm, which earlier studies have linked to abnormal growth and even cancer.
Previous research has suggested that smoking marijuana can lower sperm count, or the number of sperm in semen when it’s ejaculated. This new study, however, is the first to link THC concentration in urine to sperm count.
The study also found that the sperm count of the men who didn’t smoke weed was about twice as high as it was in the smokers. Yep, that’s a big difference.

“How do you even reconcile that, biologically, an entire pathway is going to be affected by these changes?”

This doesn’t mean that smoking cannabis will lead future children to be more vulnerable to cancer. Murphy is very clear that this is a pilot study originally intended to see if cannabis even has any effect of this kind on sperm. The sample size is small, and they didn’t control for the concentration of THC the human recruits smoked. The scientists did, however, measure THC in the urine and noted that more THC in the urine correlated with more changes.

“This is a smaller study, but with concerning implications,” says Bobby Najari, a urologist at NYU Langone who was not involved in the study. Najari already counsels men who use marijuana regularly to cut back because of the effect on sperm count. “I think one of the important positive things about research like this is that it may further motivate men to change their health,” he adds. “It’s one thing to talk about sperm count, another when you’re talking about the potential health of the child.”

Both Najari and Murphy stress that future research needs to be done, and the Duke team is already working on follow-up studies. Are those changes reversible? Will they even end up affecting a potential baby? “I want to be very careful to not have the results turned into something that they’re not,” says Murphy. “It’s not intended to scare people. Our whole objective is to learn more about biology and what effects there might be.”


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