Hi catherinedeb
Were you actually at any of the consultations? He may be experiencing things that he has not felt comfortable disclosing to a parent, but will disclose when asked by a health professional. What I am getting at is he may have borderline psychotic symptoms, hence why he would be prescribed an anti-psychotic.
In my experience, having been diagnosed on some occasions with Aspergers Syndrome and other occasions Paranoid Scizophrenia or Scizoaffective disorder, I have come to understand that there is a significant cross-over between the 'negative symptoms'* of a psychotic illness and what you would observe in someone who is considered Autistic
* (in this context negative does not mean bad, it means lacking)
That is to say, while someone who has ASD typically does not experience delusions or hallucinations, they do exhibit issues such as taking phrases literally, and having diminished social imagination/communication, which are equally seen in an illness like schizophrenia.
My experience with anti-psychotics is that they really do help, but that several may have to be tried before finding the right one. Side effects are a real issue, for example some will cause weight gain, which itself can have many knock on consequences in the long term if not managed.
One thing to be wary of, is whether these clinicians have taken into account your son's Autism when carrying out the consultations. There is scope for mis-communication even by professionals who should have some knowledge of ASD.
Another longer term concern is how the dosage will be managed. There is a tendency for dosage to creep higher and higher, following future consultations, perhaps exacerbating the problems and introducing more side effects with little gain. It can be very difficult to reduce the dosage once it has gone too high. Healthcare professionals commonly react to symptoms rather than being proactive, and will never consider reducing a medication dosage if it seems to be 'working'.
I am not qualified in psychology or medicine, these are my personal experiences and opinions, so I would seek advice from others. I think he is lucky to have someone like you looking out for him, many people do not.