My daughter is six and still does this, but she is non verbal and low functioning. We were told it is not easy to stop, or not even be possible, it has slowed down a bit since we started her with a lot of ABA and using sign language, and PECS, but she still does it when she gets upset. The school and her therapists have trained her to use a pillow when she does bangs he head now, and we tell her to go be safe which to her mans go to her bed and do it there.

We have been told it is frustration and anxiety that causes it, so just to slow it down and fer her to do it in a more safe manner is a plus. My daughter his a lot of sensory issues, so again they said it may neer go away. She also hits herself when she gets upset, and distrcting does not work, the best thing to do is just leave her alone and let her work her way out of it, because trying to redirect was making things worse. This is why all autistic children are diffent I guess.

Whenever it gets bad we have the doctor check for ear infection, vision problems, teething, food intolerances and/or headaches first. I also try to make sure there is nothing like dandruff, dry scalp that may be making her itch or uncomfortable.

We use a weighted blanket that she is able to put over her head while sitting in a rocking chair. I think it might work because she gets the pressure from the blanket while also getting the input from the rocking motion. She has her own chair and blanket set up in a quiet corner and she will cover her head and face with the blanket and rock until she gets regulated. It doesn't work all the time but it helps her sometimes. I am going to try to add the ambiance app and/or noise cancelling headphones to the mix to see how that works.

I have also tried:
-deep pressure massage to the head
-vibrating hair brush
-headband/hat tight enough to exert a little pressure
-weighted cap

My little one (3yrs old now, 1.5 yrs old then) used to do a lot of head banging before he was diagnosed (PDD and sensory issues) and now he only does it on occasions. One of the things that his therapist told me to do when I brought it up (when it first started) was distract him. She said instead of bringing focus to it by mentioning it, to simply distract him with a toy, song, book or anything else that would peek his interest. This seemed to help and as his vocabulary increases his head banging has decreased. Perhaps it might help to help him find non-verbal ways to communicate, since you mentioned this got worse when he lost his speech. I've downloaded free apps that help toddlers/small kids communicate via these apps. This might help also. I wish I could actually help out, I can only imagine what you are going through. Good luck and I hope it gets better.

My son never did any head banging but I have heard from other parents that the diet helps a lot, specially going casein and gluten free. We have done it, and I have notice that for my son milk made a major difference, and there are many options like rice milk, almond and coconut. We use almond because he is on a gluten free diet so he already eats lots of rice, and coconut it's sweeter (we also try to avoid high sugar items). Our son was loosing his speech, we have been in our gluten casein free diet for 9 months and this is one of the things that I seen work.

Does he like smart phone games? My son loves Angry birds and is willing to do pretty much anything I say in order to play. Including stopping harmful behavior like head banging.