NASHVILLE, Jan. 21 (UPI) -- Human male fertility may be impacted by long-term exposure to marijuana, researchers in the United States and Japan suggest.

The researchers at Vanderbilt University Medical Center in Nashville and colleagues said the findings show that genetic loss of fatty acid amide hydrolase -- an enzyme -- results in elevated levels of anandamide, an endocannabinoid, in the male reproductive system, leading to compromised fertilizing capacity of sperm. The endocannabinoid system refers to a group of lipids and their receptors that are involved in a variety of physiological processes including appetite, pain-sensation, mood and memory.


Retention of fatty acid amide hydrolase on an egg provides evidence that the sperm's capacity to penetrate is dampened by elevated anandamide levels.

These findings, published in the Biology of Reproduction, point to previously unsuspected pathways regulating sperm function.

But perhaps more importantly, the results are of great clinical significance because sperm of chronic marijuana users, as well as sperm in fatty acid amide hydrolase-mutant males are exposed to enhanced cannabinoid/endocannbinoid signaling, the researchers said.