Although marijuana and THC, its biologically active constituent, are most well-known and well-studied for their roles in and influence on the nervous system, evidence of their reproductive effects has also emerged from research done on lab mice. However, only very recently was the first study conducted to assess how smoking marijuana is associated with sperm and reproductive hormone quality in men.
The study took place at the Massachusetts General Hospital Fertility Center, with the participation of 662 males from couples experiencing difficulties conceiving. The scientists found that within this group, men who had smoked marijuana, either prior to or at the time of the study, had an average sperm concentration of 62,7 million/mL. This was significantly higher than those who had never smoked marijuana, who had an average sperm concentration of 62,7 million/mL. A similar pattern was observed for total sperm count. Furthermore, the prevalence of sperm concentration and total sperm motility below WHO reference values among marijuana consumers was less than half that of marijuana non-users. Finally, there was no difference in serum testosterone level between men who had and had never smoked marijuana.
Although these findings might not be perfectly representative and generalizable to all men, as the study was conducted on those who experienced challenges conceiving, to certain extent, they still contradicted the concern that marijuana poses deleterious effects on testicular function.