December 24, 2018
Men who use recreational marijuana should consider halting use of the drug at least six months before they try to conceive, researchers at Duke University suggest.
Tetrahydrocannabinol (THC) – the key psychoactive component of cannabis – impacts that genetic makeup of the user's sperm, triggering structural and regulatory changes, according to a study published in the journal Epigenetics earlier this month.
THC appears to impact hundreds of different genes, but many of the genes are associated with two major cellular pathways, researchers said. One pathway helps bodily organs reach their full size. The other involves genes that regulate growth during development.
Scott Kollins, a psychiatry and behavioral sciences professor, said the impact of cannabis use on the reproductive health of men is not completely known. Much remains to be discovered, but something about cannabis affects the genetic profile in sperm.
"We don't yet know what that means, but the fact that more and more young males of child-bearing age have legal access to cannabis is something we should be thinking about," Kollins said in a statement.
The study examined the impact of THC in rats and 24 men. Men with higher concentrations of THC in their urine experienced more pronounced genetic changes to their sperm.
The fact that more and more young males of child-bearing age have legal access to cannabis is something we should be thinking about. -- Prof. Scott Kollins
Susan K. Murphy, chief of Duke's division of reproductive sciences, stressed that researchers do not know what impact this has on developing children. For instance, researchers don't know whether sperm impacted by THC are healthy enough to fertilize an egg and continue its development.
The study is limited by a small study population and served as a starting point for research into the effects of THC on sperm, Murphy said. Additionally, the findings could be confounded by other factors impacting the sperms health.
"In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there," Murphy said in a statement. "We don't know whether they are going to be permanent. I would say as a precaution, stop using cannabis for at least six months before trying to conceive."
Researchers intend to examine whether the changes are reversed once men stop using marijuana. They also expect to expand their study populations.
The research comes as more states legalize recreational marijuana. Ten states and Washington D.C. have legalized recreational marijuana. More could be on the way.
The New Jersey legislature is considering legalization and has the backing of Gov. Phil Murphy. New York Gov. Andrew Cuomo has made legalizing marijuana a priority for the first 100 days of his third term. And Pennsylvania Gov. Tom Wolf has said it's time to take a serious look at legalization in the Keystone State, though a bill seems unlikely to pick up steam in the General Assembly.
The research was funded by a grant from the John Templeton Foundation.