I have not yet finised reding or even scanning Aspergirls, but I know that in it is a part on mutism in (Asperger’s) autistics. I also recall that in 2003 or 2004, I was on an autism discussion board and selective mutism was regularly discussed. Not necessairly in the context of autistic kids or adults, but as a similar disorder.
Indeed, many autistics, myself included, have symptoms that could minmic selective mutism, where a person is able to speak in certain situations but not in others. A person cannot technically be diagnosed with both selective mutism and an autistic spectrum disorder, since when a person is autistic, their selective mutism symptoms are chalked up to that.
I do not know what the literature says about this, so I can only speak for myself, but I often get “locked up inside” out of anxiety. For example, in high school, when my tutor raised topics that hit too close to home, I shut down. However, I can also experience mutism when my thoughts get interrupted or I’m overloaded. Then, my brain shuts down in another respect.
So what can parents and teachers do about selective mutism in an autistic? What they did to me, both my parents and my teachers, was force me to speak. I remember one night when I was about sixteen, being made to stay up until I’d told my parents a certain rather personal thing. Let me say, thhis is not the way to go. Anxiety may play a factor in selective mutism symptoms. When you use force, this anxiety will only get worse. Also, if your child does not trust you enough to talk to about personal issues, that’s something to work on first.
When the root of the mutism is not anxiety, still, force will not work. When a person is overloaded, the words and actions you use to make them speak, will often only overwhelm them more. Let them quietly think for a bit instead. You might want to ask what the autistic needs – quiet time to process, an alternative communication modality, etc. -, and the person may be able to indicate this in a way even if they don’t use words. Sometimes, asking questions will help, at least with me, but sometimes, this will distract me only further from what I wanted to say.