According to the World Health Organization, 147 million people use cannabis all over the world, making it the most widely used drug.

However, in addition to psychoactive effects experienced by many users, cannabis use also has a number of health consequences, including lowered sperm count.

This may not be the only effect the drug has on men's fertility; cannabis can alter the genetic makeup of sperm in regular users too.



Cannabis is the most widely distributed and consumed drug in the world.

In fact, according to the World Health Organization, it's used by about 147 million people each year — that's around 2% of the world's population.

Use of opium or cocaine, on the other hand, is restricted to only 0.2% of the population.

There's something about cannabis use that affects the genetic profile in sperm. Thomson Reuters

However, in addition to psychoactive effects experienced by many users, caused by the cannabinoids cannabidiol (CBD) and tetrahydrocannabinol (THC), cannabis use also has numerous health consequences, such as impaired cognitive development and a reduced sperm count.

According to research published in journal Epigenetics, scientists at the Duke University Medical Centre in Durham suggest the drug can also affect sperm's DNA.

Cannabis influences metabolic pathways and gene regulation of sperm DNA

As part of their work, the researchers looked at experiments carried out on rats in addition to conducting a study on 24 male subjects.

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The study compared the sperm of "regular" cannabis users — those who have smoked the drug at least once a week in the past six months — with a group who had used cannabis no more than ten times in the past six months.

In these studies, the researchers found that the THC in the drug attacks genes in two metabolic pathways responsible for organ growth and growth regulation during development and that it ultimately affects DNA methylation.

The effects of cannabis use on males and their reproductive health are not completely null. Anthony Bolante/Reuters

Methylation, a natural regulatory process, transfers methyl groups to DNA bases, resulting in a reduction in activity in these segments — basically, it changes gene expression. As the researchers have now been able to show, the THC content of cannabis influences this process and changes the genetic structure of the sperm.

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"What we have found is that the effects of cannabis use on males and their reproductive health are not completely null, in that there's something about cannabis use that affects the genetic profile in sperm," said Scott Kollins in Duke Health News and Media, one of the authors of the study. "We don't yet know what that means, but the fact that more and more young males of child-bearing age have legal access to cannabis is something we should be thinking about."

More studies with cannabis users are needed to draw further conclusions

Whether or not the changes observed are permanent, to what extent they're hereditary, and whether or not they can influence the resulting child's development is still unclear, according to Susan K. Murphy, lead researcher of the study.

It can't yet be ruled out that the results may have been influenced by other factors such as, for example, the diets or the sleep patterns of the study's participants.

One of the researchers suggested it was best to assume the changes to the DNA of cannabis users will also be present with the subsequent generation. 102642344@N02/Flickr

"We know that there are effects of cannabis use on the regulatory mechanisms in sperm DNA, but we don't know whether they can be transmitted to the next generation," Murphy explained. "In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there."

In the future, the researchers are looking to continue their investigations in larger studies to ascertain whether the structural changes in the sperm DNA can be reversed and whether changes are passed on.