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New study shows use of cannabis could hurt sperms, affect fertility

Use of cannabis by men of child-bearing age significantly alters their sperm and affects fertility, a new study has shown, re-igniting the age-old debate of the effects of the plant.

The study conducted by Duke University Medical Centre revealed that use of bhang by men causes potential risk to their future children as the active ingredient of the drug, tetrahydrocannabinol (THC), causes sperm to change.

“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 Dr Scott Kollins, professor in psychiatry and behavioral sciences at Duke University and senior author of the study funded by the John Templeton Foundation.

The research paper, “Cannabinoid exposure and altered DNA methylation in rat and human sperm,” published on December 19, studied the effects of THC in both humans and male rats with a view to find out the effect of the drug before conception took place.


It was discovered that the chemical affects epigenetics, triggering structural and regulatory changes in the DNA of users’ sperm.

According to, “epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do not involve changes to the underlying DNA sequence, a change in phenotype without a change in genotype, which in turn affects how cells read the genes.”

Epigenetic change is a natural occurrence that can also be influenced by several factors including age, the environment or lifestyle, in this case, the use of marijuana (bhang), and disease state such as cancer.

“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 (in the US) is something we should be thinking about,” Dr Kollins said.

Experiments in rats and a study with 24 men found that THC appears to target genes in two major cellular pathways and alters DNA methylation, a process essential to normal development.

DNA methylation is an epigenetic mechanism that occurs by the addition of a methyl (CH3) group to DNA, thereby often modifying the function of the genes and affecting gene expression.


According to lead author Susan Murphy, an associate professor and chief of the Division of Reproductive Sciences in obstetrics and gynecology at Duke University, one of the pathways affected by use of the drug is involved in helping bodily organs reach their full size while the other pathway involves a large number of genes that regulate growth during development.

“In terms of what it means for the developing child, we just don’t know. It is unknown whether sperm affected by THC could be healthy enough to even fertilize an egg and continue its development into an embryo,”Dr Murphy said.

The study also revealed that in humans, cannabis use was also associated with significantly lower sperm concentration. She suggests that men who would like to conceive should stop using the drug at least six months before trying for a baby, in case the effects can somehow be passed on to the next generation.

The study shows that about 150 million people worldwide use the drug and its use may continue to grow as it becomes more accepted. Medical use of marijuana is legal in 33 American states.

The potential effects of bhang use are very close home since in September Kibra MP Ken Okoth wrote to Speaker Justin Muturi asking for facilitation in preparing the Marijuana Control Bill.