Does Pot Use Really Affect Sperm Count?

By Paul Gaita 01/02/19

A Duke University study explored the possible correlation between THC concentrations in urine and viable sperm count.

doctor talking to male patient about his sperm count

The research on whether marijuana can have a detrimental effect on sperm production in men has produced varying results, with some studies suggesting that usage may result in a lower sperm count and/or abnormal sperm genetics, while others claim no correlation exists.

New research from Duke University Medical Center supports the former position by showing that high concentrations of THC – the compound in marijuana that produces a euphoric response – in urine appeared to correspond to a lower sperm count as well as changes to the DNA structure of the sperm. Though the test subject group was limited to 24 participants, and additional research would be required to identify the specific risks of marijuana use to sperm, the study data did appear to correspond to results from previous studies.

According to Live Science, the Duke University study – published in the journal Epigenics – is the first to illustrate the correlation between THC concentrations in urine and viable sperm count.

Of the 24 participants – 12 of which were marijuana users and 12 of which were not – the sperm concentration in the latter group was twice as high as that of the former group. The study also noted epigenetic changes in sperm DNA among the former group – alterations to the "chemical tags," as Live Science described them, that regulate gene expression. 

The higher the concentration of THC in the test group's urine, the more significant the changes to the sperm DNA, most notably in genes that help bodily organs reach their full size and for basic growth during development. A corresponding study on rats revealed a similar pattern in the same genes. However, such changes may not be permanent; sperm, damaged or not, are reabsorbed in the body if not ejaculated after 70 days.

As lead author Susan Murphy – chief of the Division of Reproductive Sciences in the Department of Obstetrics and Gynecology at Duke – noted, "The sperm DNA . . . is not mutated in the traditional sense" by marijuana, and "epigenic alterations can affect gene regulation without changing the DNA sequence." 

Ultimately, the study could not determine whether the changes to sperm count and DNA determined by their study had an actual effect on fertilization or offspring, but Susan Murphy suggested that damaged sperm could have an adverse effect if it resulted in a viable embryo. In that case, individuals who are trying to conceive should consider abstaining from marijuana use 

"In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there [in sperm]," she noted. "I would say, as a precaution, stop using cannabis for at least six months before trying to conceive."

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, and The Los Angeles Beat, among many other publications and websites.