Marijuana causes alters genetic makeup of sperm

A new study has revealed that cannabis or marijuana can alter the DNA or genetic make-up of the sperms and this can have long term consequences in the baby born of that sperm. The study results were published in the latest issue of the journal Epigenetics.

Marijuana. Image Credit: ShutterstockProfessional / Shutterstock
Marijuana. Image Credit: ShutterstockProfessional / Shutterstock

Researchers at the Duke University used laboratory rats. They divided the rats into two groups. One of the groups was given tetrahydrocannabinol (THC) while the other was not. THC is the active ingredient of cannabis that causes the high and other psychological symptoms. As a second part of the study the team collected sperm samples from 24 men who smoked marijuana weekly. They also collected samples of sperms from control men who had smoked pot not more than 10 times in their entire lives and had not smoked pot over the last six months before the study. Results showed that in both rats and humans, there was a significant change in the genes in the sperm cells as a result of using marijuana or being given THC (as in the cases of the rats).

DNA in the sperms codes for the functional activities of the cell and this sperm becomes half of the embryo that would develop into the baby. The DNA has specific instructions that allow for protein synthesis and other functions explained Professor Susan Kay Murphy, professor of gynecology at Duke and co-author of the study. She said that these chemicals such as THC can alter the DNA in such a manner that the necessary instructions may not be followed while unnecessary bits of the DNA may become active. It affects two major pathways, the authors write. One of them is associated with methylation of DNA while the other shows that these chemicals may change the structure of a segment of the DNA without altering its final functions.

She warned that these alterations can change pathways of how the instructions work and this can be seen in both rats and humans in the study. This could alter the development of an organ in future or even raise the risk of a cancer, she said. She said, “How do you even reconcile that, biologically, an entire pathway is going to be affected by these changes?” She added however that smoking pot does not cause cancer in future children but the study, albeit small, proves that rise in THC in the urine samples of the individuals who smoked pot was associated with more genetic changes.

Experts have urged men to refrain from smoking pot while trying to conceive. This is also because of the earlier evidence that smoking pot can cause lowering of sperm count in general. The team at Duke University intends to conduct further larger studies to be sure of their findings. They have warned that this study is not aimed at scaring people but the objective of the study is to understand the underlying effects of THC on the sperms. “In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there. We don't know whether they are going to be permanent. I would say, as a precaution, stop using cannabis for at least six months before trying to conceive,” said Dr. Murphy.

At present around 180 million people use cannabis for recreational purposes globally, write the authors. They add that 20.6 percent men aged between 26 and 34 years admit to using cannabis over the past year according to the National Survey on Drug Use and Health report in 2015. Authors write, “Since mean paternal age for first child in the United States is 27.4 years, a substantial number of males of child-bearing age may have recent exposure to cannabis at or around the time they conceive.”

Lead author Professor Scott Kollins said, “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…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.”

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.



  1. Samuel Brown Samuel Brown United States says:

    We already knew there was an affect. The question is: what kind? "This study is not aimed at scaring people." However, a small study found few results. We've seen studies like this before. Give us more data. Nor research. More solid findings. Don't just say "there's an affect. It must be bad." That is propaganda and not helpful. Alcohol has an affect on sperm count and genetic makeup but not so big as to result in the outlawing of alcohol. Prohibition is a pointless excersize and preliminary research like this that (I would argue) IS aimed at scaring the public and lawmakers is dangerous and unhelpful. This study was done to influence lawmakers and probably funded by pharmaceutical companies because cannabis is easy to access and hard to control. If it can replace high priced medications then market shares of big pharma will go down. If we had healthcare that didn't overcharge people for medication, cannabis would already be legal. This is not a properly done study, nor is this a well written scientific article. Where is the data from the study? Where are the numbers? How much THC did they inject into the rats? How much were the human participants smoking? What actual affects were there on the genetics of these people? Methylation occurs all the time. Diet affects methylation. Stress affects methylation. Environment affects methylation. Most importantly methylation is completely natural and almost never affects HOW genes are transcribed into protein. It usually changes WHICH genes are transcribed into proteins. Know your genetics people. Don't be fooled by broad BS statements like the ones in this article. That being said, yes, cannabis use does affect sperm. But again, we already knew that. This is study was a waste of time and money.

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