Although masturbation in itself is pretty harmless, when it becomes an addiction it will start to interfere with your life. It is not so much that masturbation gives you a low self-esteem, but rather the other way around, that people who have a low self-esteem - preventing them from courting in the normal manner - resort to masturbation as the only sxual outlet for unrequited intimacy with real women.
Thus, it is a self-esteem matter that can cause addictive behaviour of one kind or an other. You'll find if you get rid of the negative self-image, your social life will improve and masturbation will not be the ONLY sexual outlet in life.
The Positive Ego Training Program