Cannabis risk to male fertility

SPERM from men who regularly smoke cannabis may fail to fertilise eggs because of premature “burn-out”, scientists said yesterday.

A study showed the sperm move too fast, too early and their numbers were also reduced. Cannabis smokers also produced significantly less seminal fluid than non-drug takers.

The findings, presented yesterday at the annual meeting of the American Society of Reproductive Medicine in San Antonio, Texas, suggest that cannabis use can impair male fertility.

Scientists from the University of Buffalo School of Medicine in New York compared sperm from 22 cannabis smokers and 59 fertile men who had produced a pregnancy.

Sperm were tested for their numbers and ability to move. Chief researcher Dr Lani Burkman said: “The sperm from marijuana smokers were moving too fast, too early. The timing was all wrong. These sperm will experience burn-out before they reach the egg and would not be capable of fertilisation.”

The volunteers who smoked cannabis were all frequent users who had taken the drug an average of 14 times a week for about five years.

Dr Burkman said many men who smoked cannabis had fathered children. But it was likely cannabis could push a man with naturally low fertility “over the edge into infertility”.

No-one yet knew how long lasting the effects of cannabis on fertility might be, or whether they were reversible.

“I definitely would advise anyone trying to conceive not to smoke marijuana, and that would include women as well as men,” Dr Burkman said.