Marijuana use may lower sperm counts "quite a lot"

Sperm counts have been decreasing for decades. Still hasn't kept us from having more people than the earth can sustain.

Marijuana enthusiasts like to find studies that show marijuana killing cancer cells in test tubes. If it kills cancer cells, it very possible it might kill non-cancer cells.

http://www.cbsnews.com/news/marijuana-lower-sperm-counts/

By Agata Blaszczak-Boxe Livescience.com September 1, 2015

Smoking marijuana more than once a week may lower men's sperm counts by about a third, according to a new study.

Researchers found that the men in the study who smoked marijuana more than once a week had sperm counts that were 29 percent lower, on average, than those who did not smoke marijuana, or used the drug less frequently.

The researchers thought that amount of reduction in sperm count "was quite a lot," said study author Tina Kold Jensen, of the University of Copenhagen in Denmark.

They also found that the sperm concentrations (which is measured slightly differently than sperm count) were 28 percent lower in the men who smoked marijuana more than once a week.

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Moreover, in the men in the study who smoked marijuana and used other recreational drugs, the sperm counts were reduced by 55 percent, and the sperm concentrations were reduced by 52 percent, compared with men who hadn't used the drugs.

The researchers found that the men who had smoked marijuana in the past three months were also more likely to smoke cigarettes, and consumed more alcohol and caffeine than those who had not.

These lifestyle factors also could have affected the men's sperm levels, so the researchers took them into account, and the link between marijuana and lower sperm levels held. However, the study still does not prove that the drug caused the lower sperm counts, Jensen said.

"We cannot exclude the possibility that the men who used marijuana generally have an unhealthier lifestyle and health behavior, which may also affect their semen quality and hormone levels," the researchers said in the study.

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