Our definition of autism, like many psychological conditions, is based on symptoms--behavior and development--not causes. We're learning more about the underlying reasons why brains work the way they do, so that may change eventually. But right now, if you have a large number of autistic symptoms, you most likely meet the diagnostic criteria for ASD.
In young children, the visible symptoms of autism may mimic other developmental conditions, so a professional diagnosis is important. An intelligent adult can make the distinction for themselves, given enough information. (Though they'll still need a diagnosis to seek treatment or accommodations.)
> Our definition of autism, like many psychological conditions, is based on symptoms--behavior and development--not causes.
That's also true of many physical conditions with unknown causes, hence the comparison to pre-knowledge-of-HIV AIDS as a more apt comparison than a rash.
> But right now, if you have a large number of autistic symptoms, you most likely meet the diagnostic criteria for ASD.
By DSM 5 criteria, you need either two or three symptoms (depending on exactly where you bound así for symptom) symptoms, manifesting by a particular time, with specific social impact, and all the potential symptoms (and the impact) are defined in a way that even an intelligent
layman in a position to be objective rather than applying a bias from their own position is likely to have trouble applying them well.
In young children, the visible symptoms of autism may mimic other developmental conditions, so a professional diagnosis is important. An intelligent adult can make the distinction for themselves, given enough information. (Though they'll still need a diagnosis to seek treatment or accommodations.)