Cannabis Use in Men Linked to Changes in Sperm DNA and Higher Miscarriage Risk, Studies Find

New research from Duke University and Boston University is shedding light on a lesser-known factor that could influence fertility and early pregnancy outcomes—male cannabis use.

According to the studies, the use of cannabis may alter sperm at a genetic level, potentially increasing the risk of miscarriage and affecting early embryo development. Scientists point to tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis, as a key driver behind these changes. THC appears to trigger what researchers call epigenetic modifications—chemical changes that affect how genes are turned on or off without altering the DNA sequence itself.

Researchers at Duke University found that regular cannabis exposure can disrupt DNA methylation patterns in sperm, particularly in genes that play a critical role during the earliest stages of embryonic growth. These changes were more pronounced in individuals with higher levels of THC in their system, suggesting a direct link between cannabis use and genetic alterations in sperm.

The findings are especially significant during a crucial developmental window known as the maternal-to-zygotic transition. This is the stage where control of embryo development shifts from the mother’s genetic material to the father’s. If the sperm carries altered genetic instructions, it may disrupt this process, potentially leading to stalled development or pregnancy loss.

Supporting these findings, a separate study conducted by Boston University tracked over 1,500 couples trying to conceive. The research found that men who used cannabis at least once a week were linked to nearly double the risk of miscarriage in their partners—even when the women did not use cannabis. The increased risk was most noticeable during the first eight weeks of pregnancy, a period when the embryo is highly sensitive to genetic signals.

Further analysis also identified changes in a gene known as DLGAP2, which is associated with brain cell communication and has been linked to certain neurodevelopmental conditions. Experiments in animal models suggest that these genetic changes could potentially be passed on to offspring, raising concerns about long-term effects beyond pregnancy.

Adding to the concern is the increasing potency of modern cannabis products. THC levels today are significantly higher than in previous decades, which may amplify the extent of these genetic changes.

Based on these findings, researchers are advising men who are planning to conceive to consider avoiding cannabis use for several months. This allows time for the body to produce new sperm that are less likely to carry these epigenetic alterations, potentially improving the chances of a healthy pregnancy.

As conversations around fertility often focus on women, this research highlights the important role male health and lifestyle choices also play in successful conception and early development.