The Effect of Marijuana on Sperm
Regular marijuana usage (more than once a week) is associated with a negative impact on sperm count and overall quality, but they are still investigating the exact mechanisms behind this association.
In a 2015 study, over 1,200 Danish men aged 18-28 (peak fertility is most likely between the ages of 25-29) were surveyed and their sperm analyzed. Researchers found that the men who consumed marijuana more than once a week had a 28% lower sperm concentration than the control group of non-smokers, and this percentage was significantly higher, 52% lower, for those who combined marijuana with other recreational drugs. Overall, the Danish study found that sperm count and motility were significantly lower in the group that claimed to smoke marijuana more than once a week.
The brain is not the only place THC can bind; sperm have receptors (CB1 & CB2) for cannabinoids that are present in marijuana. At least two studies have shown that activation of these CB1 and CB2 receptors in sperm significantly decrease sperm motility. Motility is a term that refers to a sperm’s capacity to swim well enough and at the right time (e.g.: not swimming too fast at the outset and therefore losing steam) to “find” the egg.
These researchers found that not only motility was affected, but that THC exposure on these CB1 and CB2 receptors was associated with an inhibiting effect on capacitation-induced acrosome reaction.
Capacitation is one of the many changes that sperm need to undergo after ejaculation in order to penetrate the egg. The acrosome reaction involves a series of changes that the cap of the sperm undergoes in order to fertilize the egg.
Marijuana and Female Fertility Problems
There are relatively few studies showing concrete evidence that marijuana use negatively affects women’s fertility.
A 1990 study by Muller et al. suggested that female marijuana smokers could be more prone to abnormal ovulation patterns such as delayed ovulation, especially if they used marijuana during the year that they would be trying to conceive. Other studies point to a strong possibility that regular smokers are at a slightly higher risk of anovulatory cycles (not ovulating at all).
A 2016 report points to studies that suggest marijuana is associated with a disruption in the menstrual cycle resulting in an increased rate of anovulatory cycles (no ovulation occurring).
Generally, it is thought that marijuana can affect the production of luteinizing hormone in women. Luteinizing hormone (LH) is responsible for testosterone production in men and for stimulating ovulation in women. Studies show that men who are frequent smokers tend to have lower than average levels of testosterone, and that female smokers may have lower levels of LH.