“these findings are not consistent with a deleterious role of marijuana smoking on testicular function as initially hypothesized,” chavarro and his colleagues report this week in the journal human reproduction .
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one widely circulated 2014 study involving nearly 2,000 british men — the world’s largest study to explore how common lifestyle factors influence sperm morphology (the size and shape of sperm) — found that males under 30 with less than four-per-cent normal sperm were nearly twice as likely to have used cannabis in the previous three months. no similar associations were found with body mass index, type of underwear, smoking, alcohol consumption or having a history of the mumps — though the researchers did find that sperm size and shape was worse in samples ejaculated in the summer months.
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