Could excessive masturbation be a sign of a mental or physical condition?

What's excessive?: It becomes excessive only when it consumes so much time that you miss other important aspects of life, or the imagery / act becomes obsessive. Only you can tell if your life is going off-course and this is an unwanted behavior unlike what your friends have. Talk with a few friends, your physician, and perhaps even a parent (!) and decide if it's interfering with a good life.

Addictive behaviors: to include masturbation may be signs of lack of emotional balance.