Marijuana contains cannabinoids and affects sperm physiology. The consequence of this is that sperm cells consume more energy than usual. Therefore, when they reach the female reproductive system, they do not have enough energy to pass through the egg and fertilize it. This is why marijuana is said to affect male fertility.
In addition, marijuana has other effects on male reproductive capacity. This drug causes a decrease in testosterone levels in men and a lower libido or sexual desire. Men who smoke marijuana have also been seen to have erectile dysfunction.