Well his best bet would be to go in for a doctors appointment. It could be passable that the marijuana was masking a previous condition, or created one. Loss of sex drive could be from low testosterone levels. And theres so much more one needs to know. Past smoking habits, age, other drugs and medications one might be on, family history. Don't be afraid to ask a doctor face to face. If they can preform a lower GI on me they can easily take anything you can throw at them.