While most studies investigating the link between cannabis and male fertility have shown a negative correlation, some suggest the opposite. As such, although it seems that cannabis has an impact on male fertility, further research is needed before firm conclusions can be drawn.
One such study suggesting a negative relationship between cannabis and male fertility was conducted in 2015. From 1,215 Danish men aged between 18 and 28 years old, researchers found that those who smoke cannabis more than once a week tend to have a 28% lower sperm concentration and a 29% lower total sperm count than those who do not smoke marijuana.
The researchers further found that those who smoke marijuana are also more likely to use recreational drugs. In turn, those who use both marijuana and recreational drugs were found to have a 52% lower sperm concentration and 55% smaller total sperm count than those who abstain from both.
Another study, however, from 2019, reflected opposite results. In this study, from a cohort of 662 men who attended a fertility center, researchers found that men who either currently smoke marijuana or who have done in the past tended to have a higher sperm count than those who never used the substance. While interesting results, the researchers pointed out that their results were based on self-reports rather than clinical measures and may be inaccurate.
In the meantime, other studies have found that cannabis usage may affect sperm motility (its ability to ‘swim’), its shape, and even its genetic makeup. A study by Duke University in 2019 from 24 people, for example, found that tetrahydrocannabinol (THC) alters DNA methylation and thus may lead to autism.
To conclude, while further research is needed to certify the effects of cannabis on sperm count and quality, the evidence thus far seems to suggest it has a negative effect. While it does not mean that men who smoke cannabis are doomed to infertility, existing research may provide guidance to those wishing to conceive.