I really believe that marijuana does effect a man's sex drive, due to my experience with someone who had been smoking marijuana for a long period of time. This person seemed very disintrested when I would pursue different things with him that most men would love. He seemed very frustrated and I wasn't sure why. He told me it was because he had just smoked out....It's amazing how pot can change a person subtly at first, and then on to more major things such as this. It is very frustrating, when you love someone and care about them and you allow yourself to be dragged into this sort of thing.