Cannabis consumption is breaking records every year. 35 % of young men under 34 years of age report smoking it regularly*. A little firecracker can't hurt, they think. However, a new study shows that the active substance in cannabis may alter the sperm, which could alter the DNA of children born to smoking fathers.
Plusieurs studies have already shown that cannabis reduces sperm count. At a time when declining male fertility is affecting most Western countries, information had prompted doctors to add this widespread drug as a risk trigger alongside other factors such as endocrine disruptors or the environment. What wasn't known, and which has now been proven by a study published mid-December in the medical journal Epigeneticsis that the active ingredient in cannabis would alter the semen itself. Even more seriously, these alterations could have implications for the DNA and health of a potential baby.
Scientists fromDuke University compared the semen of two groups of rats: those who had received tetrahydrocannabinol (THC), the psychoactive ingredient in cannabis, and those who had not. Next, they compared the semen of 24 men who smoked marijuana weekly to that of a control group who had not used marijuana more than 10 times in their lives and not at all in the past six months. In both cases - rats and humans - marijuana changed the functioning of genes in sperm.
It should be made clear right away that scientists do not talk about DNA modification in the sense of modifying the genetic code. They are talking about an alteration of the epigenetic characteristics of DNA.
DNA could be considered as a list of instructions for making proteins; genes are subsets of this list. Our bodies make little chemical labels that biologists call methyl groups. These labels are added to our DNA in specific regions. These chemicals do not change the gene but they affect how it will be used, such as deciding which instructions will be followed and which will not. This is called DNA methylation. The process will chemically alter the basic molecules of our genome - the nucleotides - to direct them to certain functions. This process is widely known and is used to screen for certain types of cancer. Methylation does not change the genes but the way they are expressed and the nature of their function.
The study published in Epigenetics shows that cannabis use alters the way genes are expressed. This is why, in order to understand the mechanism, we talk about "reprogramming", which is certainly a bit abusive. Specifically, researchers at Duke University have identified that this alteration in methylation affects many genes involved in two different pathways. One is important for organs to grow to their maximum size, and the other plays a role in cancer and tumour suppression.
Duke's team is already working on follow-up studies. Are these changes reversible? Do they disappear after fertilization and could they end up affecting the DNA and health of a potential baby? They are not yet certain, but caution recommends avoiding cannabis use at least six months before planning a future pregnancy.
" This is a small study in relation to its sample, but with worrying implications. ' John Hultquist, director of intelligence analysis for the cybersecurity company FireEye, explained Bobby Najari, urologist at New York Langone University, who did not participate in the study. Like most of his physician colleagues, he and most of his colleagues already advise men who regularly use marijuana to reduce their use because of the effect on sperm count. « I think one of the important positive aspects of research like this is that it can further motivate men to change their behaviour. "he adds. « It's one thing to talk about sperm count, it's another thing to talk about the potential health of a child... ".
* Source : OFDT - French Monitoring Centre for Drugs and Drug Addiction
To go further :
- GreenFacts dossier Effects of cannabis use among adolescents
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