Another book you might want to read is Sensational Kids. It goes into SPD as well, but there is also things about how our nervous systems have been shown in small tests to react different than other people's. We need more evidence, but its not unstudied at all.

When it comes to "if he doesn't have SPD, is he on the autism spectrum?" There are actually multiple adult members here who are on the autistic spectrum with an SPD comorbid. I'm one of them. There are also parents here with autistic children. Especially those of us adults can reassure you that if its not just SPD, if it is more than that, people can live their lives despite it. Our lives might never be normal. We might never do what a random person off the street would expect. But we can be happy and successful in our own ways.

And really, the same thing is true for a child with SPD, they'll grow up in their own way. They won't grow up in the way that a random person off the street would expect, because they are far enough from average, whether you want to call it SPD, want to call it just another way of being, whether you want to call it part of another disorder in most cases, or what. But we grow up, we succeed in our own way, and we can be happy.

It's not a life sentence to be unusual or abnormal.

It's just more difficult to parent, more difficult to find ways to deal with, and something that not everyone understands, both as parents and as the people who are that far from average. It is different for you and for me than a random person.

But we can do it, and enjoy ourselves despite it, and in some ways, we can enjoy ourselves more because of it, and succeed in ways we otherwise couldn't because of it.

You'll find your way.