A Harvard study claims that men who have smoked marijuana at some point in their lives are more likely to have a higher sperm count than those who never used the substance at all.
Researchers from the Harvard T.H. Chan School of Public Health probed the effects of marijuana to fertility as more states approve the legalization of the recreational drug across the United States. They collected over a thousand samples of ejaculation from 662 men between 2000 and 2017. The researchers also collected blood samples from 317 participants for the purpose of analyzing reproductive hormones.
The findings appear in the journal Human Reproduction.
The Link Between Marijuana Use And Fertility
The researchers hypothesized that marijuana use can negatively impact the semen quality of male smokers. Previous studies have also found evidence that marijuana can have adverse effects on reproductive health, however, they found that the opposite is the case.
In their study, they found that men who had smoked marijuana have an average of 62.7 million sperm per milliliter of ejaculate. In comparison, men who had never smoked marijuana in their entire lives have an average of 45.4 million sperm per milliliter of ejaculate.
Only 5 percent of the 365 participants who admitted to having smoked marijuana at some point have lower than 15 million sperm per milliliter of ejaculate compared to 12 percent of the men who had never smoked marijuana.
The study, however, did not find a difference in sperm concentration from current and former smokers.
The researchers also linked greater marijuana use to higher levels of testosterone based on the blood samples collected.
Is Marijuana Good For The Reproductive Health?
"Our findings were contrary to what we initially hypothesized," stated Feiby Nassan, a postdoctoral research fellow at the Harvard Chan School and the lead author of the study. "However, they are consistent with two different interpretations, the first being that low levels of marijuana use could benefit sperm production because of its effect on the endocannabinoid system, which is known to play a role in fertility, but those benefits are lost with higher levels of marijuana consumption."
As per the higher level of testosterone among marijuana use, Nassan warned that the study does not prove causation. The findings can be interpreted as men with higher testosterone levels are more likely to engage in risky behaviors such as smoking marijuana.
The researchers also noted that the study has its limitations. Participants self-reported marijuana use. They believe that some might have underreported their habits considering that marijuana was illegal for most of the study period.
They also could not say whether the same results can be applied to men in the general population because it involved participants seeking treatment at the Fertility Clinic at Massachusetts General Hospital.