Study: Exposure to cannabis vapour adversely affects mice sperm for two generations

Researchers suggest results should give cannabis users pause.

Angela Stelmakowich 3 minute read December 3, 2021

A comparison of the exposed and control groups found that the former, immediately after the exposure period, had decreased sperm motility. / Sonsedska / iStock / Getty Images Plus

U.S. researchers report that short-term, intense exposure to cannabis vapour resulted in both male mice subjects and their sons experiencing lower sperm counts and sperm motility.

Investigators from Washington State University (WSU) discovered the multi-generational impact while exploring whether or not cannabis vapour “negatively impacts male reproductive functions and testis development in mice,” notes the study published in Toxicological Science.

Fifteen adult male mice were exposed to air alone and 15 were exposed to 200 milligrams of vaporized cannabis plant matter three times a day over a 10-day period. Although that is a high amount, WSU researchers report in a university statement “that mimics the cannabis intake of frequent cannabis users.”

A comparison of the exposed and control groups found that the former, immediately after the exposure period, had decreased sperm motility. About a month later, the sperm counts were lower.

Several of the mice in the exposed and control groups were then bred with unexposed females.

“The male progeny of the exposed group also showed lowered sperm count and motility,” the statement notes. “Cannabis-exposed sons also showed evidence of DNA damage and disruption related to sperm cell development,” it adds.

Although plasma levels of testosterone in any age or generation of mice were not affected, dysregulated steroidogenic enzymes — which are responsible for the biosynthesis of the steroid hormones — were observed in the testis of directly exposed mice, the study notes.

“The reduction in sperm count and motility of the offspring, the sons, is probably a direct effect of the cannabis exposure to father,” Kanako Hayashi, the paper’s corresponding author, says in the statement.

The next generation, the grandsons of the directly exposed male mice, “did not show the same impacts,” researchers report, perhaps indicating the sons were affected by the cannabis exposure at their developmental stage.

The results “suggest that cannabis vapour exposure generationally affects male reproductive functions, probably due to disruption of spermatogenesis (development of mature spermatozoa) in the developing testis,” the study notes.

Hayashi suggests the findings should give cannabis users pause. “This is a warning flag. You may take cannabis for some kind of momentary stress, but it could affect your offspring.”

More study is needed, with investigators reporting the results build on human and animal research that shows cannabis can impede male reproductive function.

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