Cannabis and Fertility: tracing THC in the semen of regular cannabis users

A lot of people have been asked to do a urine test, especially in cases where their employer wants to determine the presence or use of marijuana. Marijuana metabolites, which are the byproducts of marijuana intake in the body can be traced for days or sometimes even weeks after the user has consumed a THC-rich product. For all those of you who smoke weed every day, and if you decide to stop for a while, THC might remain in your body for up to 3 months, or even more.

There's one mystery question, however. Can THC be traced in sperm? According to a new study conducted by a team of researchers from Harvard Medical School, the short answer would be yes! At least in some cases. The study included 12 adult males who regularly inhaled weed. THC was traced in the "little swimmers" of two out of the 12 subjects. In addition, all samples contained at least one type of THC metabolite (THC leftovers, after the compound gets processed in the body). 

The study aimed at exploring the relationship between cannabis and fertility or pregnancies. According to the study authors, men of reproductive age "are the most common users of cannabis." Almost 20% of US adult males have declared marijuana use, while an earlier study from 2018 has further suggested that almost 17% of men and almost 12% of women reported using marijuana while attempting to conceive. 

Cannabis and Fertility: can THC influence reproduction?

The latest Harvard study does not attempt to answer how THC influences the human reproductive system nor the conceiving of a child.  The primary goal of proof-of-concept research, they explain, was to determine "if THC can cross the blood-testis barrier in certain individuals." In this respect, the study appears to have been successful. Regarding the growing data surrounding the effects of the endocannabinoid system in governing and maintaining fertility and early pregnancy, the study says, "ours is the first report that the exogenous cannabinoid THC can be detected in any reproductive matrix of every human being."

The interest in THC detection is huge, needless to say. A lot of people would like to know if marijuana could increase their potency or chances to conceive a baby.  For the purposes of the study, the researchers have focused on long-term habitual cannabis users. All participants reported they had used weed within the last month and most of them were also regular users with at least five years experience as consumers. According to the researchers, this means that the study results can't be applied for those who use marijuana occasionally.  For two participants the semen contained detectable levels of THC. The samples provided values ​​of 0.97 nanograms per milliliter and 0.87 ng/ml. But it was not clear what distinguished these two participants above.

It appeared that there is no obvious link between sperm THC and the THC metabolite concentrations in body fluids such as urine. Also, there was no correlation between when the user last used cannabis, nor their age or their weight.  Researchers commented on these finds as "surprising." They were only able to propose certain "indicators of the presence of THC in the human seed." The future directions they set with this research include identifying features that could influence the levels of detectable THC in the semen.

Some mystery questions remain

It is still a big unknown how THC affects the bodily fluids of the reproductive system, as is how it may affect conception, fertility, or childhood development. In one of the points of the study, the Harvard researchers say that the evidence at hand, related to these and similar questions, is often sparse and conflicting. 

For instance, a recent study on cannabis and fertility from Denmark suggested that regular users of smokable marijuana had fewer sperm counts than non-smokers. Another study, involving 662 elderly men with fertility issues from Massachusetts, discovered that men who had any experiences with marijuana had a higher concentration of sperm than those who never did.  While endocannabinoid receptors are recorded on the sperm itself, studies examining how THC affects human sperm remain scarce, too. Nevertheless, this is a potent field for future research. 

Since THC can be traced in the semen of some individuals, researchers might be able to soon develop a measurement method to link real-world clinical trials with previous studies in which THC was incubated directly with reproductive fluid.  Even the lowest THC concentration with which previous studies incubated sperm was more than ten times higher than the THC concentration identified in the sperm of the 12 participants from the last study, said the researchers.