Autism is a devastating neurodevelopmental disorder with a polygenetic predisposition that seems to be triggered by multiple environmental factors during embryonic and/or early postnatal life.
While significant advances have been made in identifying the neuronal structures and cells affected, a unifying theory that could explain the manifold autistic symptoms has still not emerged.
However, there is a theory that tries to explain the behavior of those who suffer from autism. The Intense World Theory suggests that Autistic people do not lack empathy/emotion.
They shut down because they are overloaded by emotions due to hypersensitivity and are not able to express empathy/emotion like other people because of that. Essentially, autistic people feel too much.