Excessive use of Marijuana over a long period of time has been found to harm the male fertility rates. This is a controversial subject, as some believe that it will not harm male fertility. However, it is in my own opinion that using Marijuana over a long period of time can cause fertility issues in men.
While this has become somewhat of an urban legend, it has not been scientifically proven that marijuana effects male fertility. While the side effects of marijuana use have been utilized to alleviate pain, and hunger, there still hasn't been any study conducted that yielded sufficient results to make the connection with male fertility.