When I have a new child come into the clinic, and I am taking a history, I ask the parents if anyone else in the family has an autism diagnosis. The answer is almost always no. But often, after weeks of therapy, one or both parents, after having learned more about autism, often state that they wonder if they have autism. (And sometimes after getting to know the parents I wonder too.) Parents of children with autism analyze their past development and either interpret or misinterpret some of their behavior as autistic. This seems to be especially true of certain high tech professions.
Much the same thing is true of other maladies such as bipolar disorder, depression, and alcoholism. But these disorders usually show up in adults and not children. So instead of parents seeing themselves as perhaps having the same autistic behaviors as their children, children, especially grown children, see (blame) their bipolar, depressive, alcoholic behaviors in their parents.
