Why do autistic kids bang their heads?

Don't really know: Fortunately, head banging is fairly rare even among children with autism, but it does occur and can be a serious health risk, possibly causing blindness and even death. People have speculated that they are trying to "raise endorphins" and even tried treatin by blocking endorphin responses, but that doesn't explain why. Behavioral techniques usually effecting in stopping; meds needed sometimes.