Dr. Greene`s Answer:
Head banging is a rhythmic behavior that is closely related to thumb sucking and body rocking. When parents see it they often get concerned about either its being a sign of a developmental problem (like autism) or that it might cause some brain damage.
Thankfully, the truth is better than most parents guess. About 20 percent of normal, healthy kids bang their heads. It usually starts soon after the first birthday and disappears on its own by about age 4.
When they have done studies of head bangers compared to peers, they usually prove to be more intelligent than average. Also, don’t be too concerned about injury. It is very difficult to truly hurt oneself that way.
Usually you can get head banging to stop more quickly by not drawing much attention to it. Try to casually distract your child away from it with something else and do not give in if he is doing it as part of a tantrum. If it is being used as a form of self-comfort, hugging and swaying can be a good substitute. There are also devices that gently vibrate the bed, which may help.
If you are very concerned, videotape the head banging and have your pediatrician watch it, just to be sure it is the normal kind and not a symptom of some other problem.