According to a recent study by a team of researchers from Harvard Medical School, sperm can contain THC.
In a study of 12 participants who regularly used cannabis by inhalation, the researchers were able to detect delta-9 THC, the main psychoactive ingredient in cannabis, in semen samples from two subjects. And at least one metabolite of THC, which remains after the body has processed the compound, could be detected in all samples.
Why focus on THC in semen? In particular to try to measure the impacts of cannabis on fertility. Men of childbearing age, the study authors note, "are the most common cannabis users, with 19.4% of men in the United States reporting using it. A 2018 study cited by the authors found that 16.5% of men and 11.5% of women reported using cannabis while trying to conceive.
How exactly THC affects the reproductive systems and development of the child are questions that the Harvard authors are not trying to answer in the study. The main objective of the research "was to determine if THC can cross the blood-testicular barrier", which they seem to have succeeded in determining.
"As part of an increase in data surrounding the effects of the endocannabinoid system on the regulation and maintenance of fertility and early pregnancy," says the study, "Our report is the first to show that the exogenous cannabinoid THC can be detected in a reproductive matrix."
Because of the need to detect THC, researchers have focused on regular, long-time cannabis users. All of the participants indicated that they had used cannabis between 25 and 30 days in the previous month, and most said that they had been regular users for at least five years. "Therefore," said the team, "the results of our study cannot be generalized to include all consumers, moderate or light."
"It is disconcerting that some, but not all, of the semen samples, tested positive for THC," says the study. "Future directions (of research) should identify the characteristics likely to affect the levels of THC detectable in semen."
It is still difficult to say with certainty and precision how THC affects sperm or the effects of THC on fertility and conception. Studies are rare and often contradictory.
A study of 1,200 young Danes, for example, found that those who smoked cannabis regularly had fewer sperm than those who did not. Another study, involving 662 older men in Massachusetts, found that men who had previously smoked cannabis had significantly higher sperm counts than those who had abstained.
"The ability to quantify cannabinoids in human reproductive tissues and fluids," they conclude, "gives us the ability to directly study the effects of cannabis on the early stages of human reproduction."