To answer this better.
"Standard diagnostic criteria require impairment in social interaction and repetitive and stereotyped patterns of behavior, activities and interests, without significant delay in language or cognitive development. Unlike the international standard,[15] U.S. criteria also require significant impairment in day-to-day functioning.[27] Other sets of diagnostic criteria have been proposed by Szatmari et al.[69] and by Gillberg and Gillberg.[70]
Diagnosis is most commonly made between the ages of four and eleven.[1] A comprehensive assessment involves a multidisciplinary team[2][12][71] that observes across multiple settings,[1] and includes neurological and genetic assessment as well as tests for cognition, psychomotor function, verbal and nonverbal strengths and weaknesses, style of learning, and skills for independent living.[12] The "gold standard" in diagnosing ASDs combines clinical judgment with the Autism Diagnostic Interview-Revised (ADI-R)—a semistructured parent interview—and the Autism Diagnostic Observation Schedule (ADOS)—a conversation and play-based interview with the child.[7] Delayed or mistaken diagnosis can be traumatic for individuals and families; for example, misdiagnosis can lead to medications that worsen behavior.[71][72] Many children with AS are initially misdiagnosed with attention-deficit hyperactivity disorder (ADHD).[1] Diagnosing adults is more challenging, as standard diagnostic criteria are designed for children and the expression of AS changes with age;[73] adult diagnosis requires painstaking clinical examination and thorough medical history gained from both the individual and other people who know the person, focusing on childhood behavior.[35] Conditions that must be considered in a differential diagnosis include other ASDs, the schizophrenia spectrum, ADHD, obsessive compulsive disorder, major depressive disorder, semantic pragmatic disorder, nonverbal learning disorder,[71] Tourette syndrome,[34] stereotypic movement disorder, and bipolar disorder.[48]
Underdiagnosis and overdiagnosis are problems in marginal cases. The cost and difficulty of screening and assessment can delay diagnosis. Conversely, the increasing popularity of drug treatment options and the expansion of benefits has motivated providers to overdiagnose ASD.[74] There are indications AS has been diagnosed more frequently in recent years, partly as a residual diagnosis for children of normal intelligence who do not have autism but have social difficulties.[75] In 2006, it was reported to be the fastest-growing psychiatric diagnosis in Silicon Valley children; also, there is a predilection for adults to self-diagnose it.[76] There are questions about the external validity of the AS diagnosis. That is, it is unclear whether there is a practical benefit in distinguishing AS from HFA and from PDD-NOS;[75] the same child can receive different diagnoses depending on the screening tool.[12] The debate about distinguishing AS from HFA is partly due to a tautological dilemma where disorders are defined based on severity of impairment, so that studies that appear to confirm differences based on severity are to be expected."
