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Tuesday, 12 December, 2000, 01:52 GMT
Cannabis clues to fertility
cannabis plants
Three separate processes were found
Scientists believe they have found a potential reason why cannabis smoking could have an effect on fertility.

The teams, from two US research units, have observed chemical reactions which are the key to both egg and sperm working properly to produce a fertilised egg.

One of the chemicals which plays an important role in these changes is very similar to a "cannabinoid" chemical found in cannabis.

While there is some evidence that cannabis smoking affects sperm production, no adverse effects on fertility have been proven so far.

Smoking a joint of cannabis
Cannabis may disrupt conception, says scientist
But Professor Herbert Schuel believes that smoking cannabis may cause an "overdose" which disrupts the delicate chemical reactions and prevents conception.

He presented his latest research to the annual meeting of the American Society for Cell Biology.

Professor Schuel found three separate processes in which the natural "cannabinoid" chemical, called anandamide, played a significant role under laboratory conditions.

In one, the actual cannabis chemical THC was also able to alter the outcome of the process.

His team found traces of anandamide in both seminal fluid and fluids in the female oviduct and egg follicles.

'Key role'

This suggests that its presence may play a key role in activating the sperm ready to fertilise the egg and any disruption to this process might affect the chances of fertilisation.

Professor Schuel said: "We know that sperm capacitation and fertilising potential are tightly regulated within the female reproductive tract.

"Within the uterus, anandamide regulates early development of the fertilised egg, and determines where the embryo will implant to initiate pregnancy. Cannabinoids also affect this process."

There are lots and lots of bits of evidence like this which never ever turn into anything significant

Professor John Henry
He added: "The increased load of cannabinoids in people who abuse marijuana could flood natural endocannabinoid-signal systems in reproductive organs and adversely impact fertility."

Consultant toxicologist Professor John Henry, from St Mary's Hospital in London, said that although the study was interesting, it was a long way from proving any risk to cannabis smokers.

He said: "There are lots and lots of bits of evidence like this which never ever turn into anything significant.

"What they are trying to do is prove a basic mechanism but a lot more work needs to be done first."

He said: "We do know that cannabis increases the risk of developing schizophrenia, lung cancer and certain head and neck cancers, but the link with fertility is not proven."

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