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How cannabis can affect sperm to reduce fertility
31st March 2004
Men who smoke cannabis could be affecting their fertility, according
to new research presented today1.
Researchers2 at Queen’s University, Belfast, have discovered
that THC – the active ingredient in cannabis – impedes
sperm motility and impairs its ability to penetrate the egg for
fertilisation.
During a multi-centre study on the lifestyle habits of infertile
men, researchers noticed that many men attending for infertility
investigations at the Royal Maternity Hospital were using cannabis
on a regular basis. This led them to commence a study looking at
the direct effects of THC.
The study by the Reproductive Medicine Research Group discovered
that THC impedes sperm motility making it less likely that the sperm
will reach the egg to fertilise it. And that another key function
of the sperm – to digest the egg's protective coat with enzymes
in a bid to aid sperm penetration – is impaired in the presence
of cannabis.
Fifty-one semen samples were used, split, and treated with THC
or simply incubated as a control. THC-treated samples were found
to be up to 45% less forward moving and up to 30% of THC-treated
sperm don’t release the enzymes needed to penetrate the egg.
Dr Sheena Lewis, from the Department of Obstetrics and Gynaecology,
who leads the Reproductive Medicine Research Group, said recent
reports carried out on sea urchin sperm suggest that cannabis may
be a major cause of infertility by inhibiting sperm functions necessary
for fertilisation.
‘These experiments on human sperm tell the same story,’
she said.
Speaking at the annual British Fertility Society annual meeting
on 31 March, Dr Lewis said: ‘Following the Government's
recent reclassification of cannabis from Class B to Class C the
need to determine its effects on male fertility is even greater
so that men can make an informed choice about smoking the drug if
it is a health risk.’
‘Infertility already affects one in six couples across
the United Kingdom and 40 per cent of these cases are due to problems
with sperm.’
Dr Lyn Whann, who presents some of the work today, added ‘It
is estimated that 3.2 million people in Britain smoke cannabis and
that figure may now increase. Add the two together and we may find
that the use of recreational drugs will exacerbate male fertility
problems.’
Notes for Editors
1The effects of Tetrahydrocannabinol (THC), the
primary psychoactive cannabinoid in marijuana, on in vitro human
sperm motility is presented at The Annual British Fertility
Society Meeting 2004 on Wednesday 31st March 2004, in Cheltenham,
UK
2LB Whann*, N McClure*# and SEM Lewis* from
*School of Medicine, Obs and Gynae, Queen’s University, Belfast
and #Regional Fertility Centre, Royal Maternity Hospital, Belfast,
Northern Ireland, UK
For more information: please contact the British Fertility Society press office
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