Masturbation occurs more commonly when a child is sleepy, bored, watching television, or under stress. Up to a third of children in this age group discover masturbation while exploring their bodies. Often they continue to masturbate simply because it feels good. Some children masturbate frequently because they are unhappy about something, such as having their pacifier taken away. Others are reacting to punishment or pressure to stop masturbation completely.
Masturbation has no medical causes.
Once your child discovers masturbation, he or she will seldom stop doing it completely. Your child may not do it as often if any associated power struggles or unhappiness are remedied. By age 5 or 6, most children can learn some discretion and will masturbate only in private. Masturbation becomes almost universal at puberty in response to the normal surges in hormones and sexual drive. It is not abnormal or excessive unless it is deliberately done in public places after age 5 or 6.