SPERM ON DOPE'S JUST A SQUIRT IN GENE POOL

It was once described by American science writer Lawrence Wright as "a
single-celled highly perishable, posterity-seeking rocket". It had many
foes, from tight underwear to pollution.

And now it seems the humble sperm has another enemy - marijuana - with new
United States researchers reporting that smoking cannabis can jeopardise
the fertility of men and women.

A research team from the Eastern Virginia Medical School and the
universities of Connecticut and California has found that cannabis alters
the delicate system by which sperm and eggs interact.

Both contain a cannabis-like substance, anandamide, naturally produced in
tiny amounts in the human body. This triggers the sperm to swim, lets the
woman's body control how fast it swims and enables penetration of the egg.

Marijuana contains a similar substance to anandamide, called THC. The
researchers found that when marijuana was smoked the THC levels went too
high, resulting in "doped" sperm which stopped swimming vigorously.

Too much THC or anandamide also inhibits the processes that allow a sperm
to penetrate an egg, team member Dr Herbert Schuel told the American
Society for Cell Biology this week.

He said the findings explained why lower fertility had been observed in
male marijuana users.

"For heavy marijuana users the study raises the possibility they are
jeopardising fertility by overloading this signalling system," he said.

A sexual health specialist at the Australian Centre for Sexual Health, Dr
Chris McMahon, said that even mid-level cannabis use - two or three cones a
day every couple of days - could affect sperm counts and sexual performance.

"Marijuana enhances the perception of sexual pleasure ... but we have also
observed that male marijuana users can experience significant sexual
dysfunction, including impotence, with symptoms lasting for up to a year,"
Dr McMahon said.

The chief executive of North Shore Fertility, Ms Devora Lieberman, said the
findings were not surprising. "We once received a sperm donation with an
alarmingly low sperm count, and upon further inquiries we discovered that
the donor was a heavy marijuana smoker."

Men who had fertility counselling with their partners were informed of the
adverse effects of recreational drugs, Ms Liberman said.

The president of the NSW branch of the Australian Medical Association, Dr
Michael Ridley, said a public health campaign was needed to inform men
about the implications of marijuana use.