Taking cannabis harms male fertility

Smoking cannabis more than once a week can drastically harm a man's fertility, lowering their sperm count by a third, experts have warned.

And when a man combines marijuana with harder drugs, including cocaine and ecstasy, the harm to sperm count was magnified.

Danish researchers found that regular pot smoking - more than once a week - was linked to a 29 per cent lower total sperm count, than those who smoked the drug less frequently or not at all.

And when a man combined regular cannabis use with other recreational drugs, their sperm count fell by 55 per cent.

It is not clear why taking marijuana damages a man's sperm count, but researchers told Livescience, it may be linked to how THC - the drug's psychoactive ingredient - interacts with specific receptors in the testes.

To arrive at their findings, researchers analysed a group of 1,215 young Danish men aged between 18 and 28.

They were recruited between 2008 and 2012, after attending a compulsory medical examination to determine their fitness for military service.

The men provided semen samples, had a blood sample taken and underwent a physical examination.

And, researchers quizzed them about whether they used marijuana and other recreational drugs, including cocaine, amphetamine and ecstasy, in the previous three months.

If the men reported taking drugs, they were asked how often on a scale from no use, to once a week and more than once a week. 

A total of 45 per cent of the men had smoked marijuana within the last three months. 

Around 10 per cent of the men had smoked cannabis in conjunction with other recreational drugs. 

They found men who admitted to regularly smoking cannabis had a sperm count that was 29 per cent lower than those who report lighter use, or abstinence.

And when other recreational drugs were taken alongside the regular use of marijuana sperm count reduced by 55 per cent. 

Researchers also noted cannabis smokers had higher levels of testosterone, within the same range as cigarette smokers.

The study authors said: 'Our findings are of public interest as marijuana use is common and may be contributing to recent reports of poor semen quality.' 

Lead author, Tina Kold Jensen, of the University of Copenhagen, told Livescience, the recorded reduction in sperm count of almost a third, was 'quite a lot'.  

Her team also noted the men who admitted to smoking cannabis regularly were also more like to smoke cigarettes, consume more alcohol and caffeine than those who did not.

Recognising these lifestyle factors could also affect a man's sperm count, the researchers took them into account when analysing the data.

Dr Jensen's team said: 'We cannot exclude the possibility that the men who used marijuana generally have an unhealthier lifestyle and health behaviour, which may also affect their semen quality and hormone levels.'

Writing an editorial to accompany the study, which is published in the American Journal of Epidemiology, Dr Michael Eisenberg, of Stanford University School of Medicine, who was not involved in the new study, said: 'It is... important to note that marijuana users were distinct in several ways to non-users.'

But, he added, the study 'provides important information for patients and providers regarding the negative association between marijuana use and semen quality.'  

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