How often are autism spectrum disorders (e.g., asperger's syndrome) undiagnosed until adulthood? how is such a diagnosis made?

Minor autism: The diagnosis is a clinical one. When issues like impaired attention and depressed mood are also present the diagnosis of Aspergers ( now termed minor autism ) is made more difficult. There are varying degrees of involment of multiple cognitive domains and behavioral features involved. No two people are alike. Get an opinion from a well trained expert in behavioral medicine who deals with autism.