Smoking weed linked with higher sperm counts, says Harvard

The counterintuitive findings bode well for stoners, but more research is needed.

  • Marijuana research in the past has found that using the drug is linked to lower testicular health.
  • New research from Harvard, however, suggests the opposite: Marijuana users have more and better quality sperm.
  • These unexpected findings highlight how poorly we understand marijuana's effect on the human body.

The opening crawl for the 1936 film Reefer Madness reads "[Marijuana's] first effect is sudden violent, uncontrollable laughter, then come dangerous hallucinations — space expands — time slows down, almost stands still... fixed ideas come next, conjuring up monstrous extravagances — followed by emotional disturbances, the total inability to direct thoughts, the loss of all power to resist physical emotions... leading finally to acts of shocking violence... ending often in incurable insanity."

Fortunately, marijuana's reputation has come quite a ways since then. Its medicinal properties are widely recognized, 10 states (as of this writing) have legalized it, and its status as a comparatively healthy alternative to alcohol and tobacco is clear. Now, new research from Harvard is giving marijuana a further bump in its reputation.

Prior research has found that marijuana usage can have a troubling side effect for men—according to a handful of studies, it reduces men's sperm counts and quality. This obviously undesirable effect, though, may not actually be the case. In fact, the opposite might be true.

Researcher Feiby Nassan recently contributed a study to Human Reproduction — it was published on February 6 — focusing on the testicular function of men who used marijuana. Between 2000 and 2017, Nassan and her colleagues collected 1,143 semen samples from 662 men at the Massachusetts General Hospital Fertility Clinic as well as questionnaires on their history with marijuana. Contrary to their original hypothesis, Nassan found that men who had smoked just two joints in their lifetime had "significantly higher" sperm concentrations. What's more, frequent users of marijuana had higher levels of serum testosterone as well.

In a press release, co-author Jorge Chavarro said, "These unexpected findings highlight how little we know about the reproductive health effects of marijuana, and in fact of the health effects of marijuana in general. […] Our results need to be interpreted with caution and they highlight the need to further study the health effects of marijuana use."

Feiby Nassan et al., 2019

Nassan and colleagues compared men who had never smoked, had smoked in the past, or were current smokers according to where they fell based on recommended fertility markers set out by the WHO. In the graph above, we can see that marijuana smokers — often regardless of whether they were past or current smokers — were more likely than non-smokers to meet these minimum healthy criteria. For example, non-smokers were more likely to have less than 15 million sperm per milliliter, more likely to have less than 39 million total sperm, and more likely to have fewer mobile sperm (i.e., sperm motility). They also had fewer progressively motile sperm, meaning their sperm failed to move in a straight line, swimming in circles instead, as well as more sperm with abnormal morphologies.

That being said, current smokers were more likely to have less ejaculate volume and more sperm with abnormal morphologies. Overall, the results suggest that moderate use of marijuana may be the best bet.

While the results seem clear, it's important to take this research with a grain of salt. Firstly, this was a correlation study: there was no way to say whether smoking marijuana caused these differences, just that they were associated. Furthermore, there's a few different ways to interpret the results. Nassan explains that there are two different possible interpretations: "The first [is that] 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." Endocannabinoids are a broad group of neurotransmitters that bind to cannabinoid receptors throughout the brain and peripheral nervous system. They handle a few different jobs in the body, including regulating appetite, mood, motivation, and—of course—fertility. Tetrahydrocannabinol, or THC, is the main psychoactive ingredient in marijuana, and it binds to these receptors, producing the high associated with the drug and potentially improving aspects of fertility.

"But," says Nassan, "those benefits are lost with higher levels of marijuana consumption." Nassan's own results showed some downsides to current marijuana use, and, as mentioned previously, prior research has shown that fertility can be reduced in heavy smokers.

The second interpretation, says Nassan, "is that our findings could reflect the fact that men with higher testosterone levels are more likely to engage in risk-seeking behaviors, including smoking marijuana." Testosterone has an array of behavioral and physiological effects in men. It's associated with both reproductive health, as well as behaviors like aggression and risk-taking. It could be that high-testosterone men seek out marijuana and other drugs, skewing the results of the study.

Ultimately, the true conclusions we can draw from Nassan's study is that we simply don't know enough about marijuana. Its pariah status has clouded the general public's understanding of its true nature. Now that its gaining broader acceptance, it's more important than ever to research marijuana and study its effects on the human body.

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An organism found in dirt may lead to an anxiety vaccine, say scientists

Can dirt help us fight off stress? Groundbreaking new research shows how.

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Are modern societies trying too hard to be clean, at the detriment to public health? Scientists discovered that a microorganism living in dirt can actually be good for us, potentially helping the body to fight off stress. Harnessing its powers can lead to a "stress vaccine".

Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.