New Zealand's edging closer to legalising recreational cannabis, but a study warns the drug's effects could hinder birth rates.
As with alcohol and tobacco, smoking marijuana comes with a risk of infertility in men, says a study published in the journal Epigenetics.
It found that higher concentrations of tetrahydrocannabinol (THC - the cannabis compound responsible for the drug's high) in participants' urine corresponded to a lower sperm count.
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Only 24 men contributed to the study, but it found that those exposed to cannabis had a lower sperm count and changes in their sperm genetic profile.
"I would say, as a precaution, stop using cannabis for at least six months before trying to conceive," says lead author Susan Murphy from Duke University Medical Center in North Carolina.
It's not the first time exposure to cannabis has been linked to lower sperm counts, but this is the first time a study has found a strong link between THC in urine and the number of viable sperm.
The findings are eye-opening: The average sperm count in semen of the 12 non-smokers who participated was around twice as high as it was in the 12 men who smoked marijuana.
While the study didn't find a direct link between changes in participants' sperm and the fertilisation and health of offspring, the researchers advise caution nonetheless.
"In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there [in sperm]," said Ms Murphy.
Other studies have come to similar conclusions. Dr Victor Chow of the University of British Columbia said last year that too much cannabis can reduce men's fertility because the drug has a similar effect on sperm as it does users.
"The weight of the evidence is that marijuana probably has a negative impact not only for sperm counts but sperm function," he said. He believes cutting back on the dope should see sperm recover quite quickly.
Others have rubbished claims of cannabis affecting fertilisation, with one study by Boston University finding no link between cannabis use and the likelihood of conceiving. But in this case the findings were based only on surveys.
The latest findings come at a crucial time in New Zealand. The Government announced on Tuesday that a binding referendum on recreational cannabis will be held during the 2020 elections - a campaign promise to the Greens.
The Ministry of Health's 2012-2013 cannabis use survey found that 400,000 New Zealanders are consuming cannabis on an annual basis. It found that 6 percent of cannabis users reported harmful effects on work, studies or employment opportunities.
Green party spokesperson for Drug Law Reform, Chlöe Swarbrick, says the positives of legalising recreational cannabis outweigh the negatives.
With similar regulation to alcohol, she says people will be safer because there is currently no way to stop suppliers from contaminating illegal cannabis with dangerous chemicals or enhancements.
But Drug Help New Zealand warns that people with mental health issues are "particularly sensitive" to the effects of cannabis. It also says chronic use can "affect fertility in both men and women".
Newshub.
