A study from the University at Buffalo has found that men who smoke marijuana have significantly less seminal fluid, a lower total sperm count and sperm that behave abnormally. The study is the first to investigate marijuana's effects on the specific "swimming" behavior of sperm from marijuana smokers and to compare the results with sperm from men with known fertility.
The lead author of the study, Lani Burkman, said that the active ingredients in marijuana appeared to have multiple effects on sperm, which in the case of less-than-optimal fertility to begin with, may make a man infertile. "We don't know exactly what is happening to change sperm functioning," she explained, "but we think it is one of two things: THC [the active component of marijuana] may be causing improper timing of sperm function by direct stimulation, or it may be bypassing natural inhibition mechanisms." In an earlier study, Burkman found that human sperm contains cannabinoid receptors, and that the cannabinoid which activates the receptors in the brain, also activates the receptors in sperm. Further research showed that human sperm exposed to high levels of THC displayed abnormal changes in the sperm enzyme cap (acrosome). When researchers tested synthetic cannabinoid equivalents on human sperm, the normal vigorous swimming patterns were changed and the sperm showed reduced ability to attach to the egg before fertilization.
In the new study, Burkman received seminal fluid from 22 confirmed marijuana smokers, along with sperm from non-users who were fertile. The samples from both groups were tested for volume, sperm-count-per-unit of seminal fluid, total sperm count, motility, velocity and sperm shape.
The results showed that both the volume of seminal fluid and the total number of sperm from marijuana smokers were significantly less than for the fertile men. "The sperm from marijuana smokers were moving too fast too early," said Burkman. "The timing was all wrong. These sperm will experience burnout before they reach the egg and would not be capable of fertilization."
Burkman said the effects of marijuana may not make men infertile but it was a risk if they were already borderline fertile. "The men who are most affected likely have naturally occurring borderline fertility potential, and THC from marijuana may push them over the edge into infertility," she explained. Burkman couldn't provide a definitive answer as to whether fertility would be restored if marijuana use was stopped. "THC remains stored in fat for a long period, so the process may be quite slow. We can't say that everything will go back to normal. I definitely would advise anyone trying to conceive not to smoke marijuana, and that would include women as well as men."
Source: University at Buffalo