Most Helpful Girl
you will get attached to masturbation and porn, and constantly want sex but you will have higher expectations. I don't recommend it. stress relief would only happen if it was once In a while. after that phase, it goes downhill.
Most Helpful Guy
As long as he is doing nothing that would physically hurt himself, or would cause him problems legally (public nudity etc) and he is not masturbating instead of dealing with day to day life, then there are no negative effects.
Positive effects, mostly stress relief, positive attitude, endorphines, reduction in depression risk that kind of thing.