There is no blood test or other biological marker for autism. Doctors rely on their own observations and what parents tell them. Psychiatry's guidebook, the Diagnostic and Statistical Manual of Mental Disorders, lays out the criteria. Many autistic traits and behaviors are seen in children without autism or with other conditions. Only in sufficient numbers and specific combinations do they add up to a diagnosis on the autism spectrum.
The three most common diagnoses on the spectrum are autistic disorder, Asperger's disorder and for children who don't qualify for those pervasive developmental disorder not otherwise specified (PDD-NOS). As this interactive checklist illustrates, there are many ways to arrive at each, and how a child is classified can amount to a judgment call. Answer questions below or select a hypothetical case to explore how a diagnosis is reached.
Were delays in social interaction, language or imaginative play apparent before age 3?
Were there delays in cognitive development, acquisition of self-help skills or emergence of interest in surroundings?
Avoiding eye contact, not returning a smile, maintaining a blank gaze, using inappropriate facial expressions or awkward body postures.
Playing alone while other children the same age approach each other, cooperate and imitate each other.
Failing to show off creative projects such as finger paintings or respond to a companion's interests, such as a plane overhead.
Failing to wave hello and good-bye, show concern for others or get excited about opening presents or seeing a parent come home from work.
Failing to point, nod head for "yes" or shake head for "no."
Can answer questions or talk about personal interests, but does not ask questions or show interest in others.
Parroting phrases from books, videos, music or another person, while not forming original sentences.
Not pretending, for instance, to drink from a teacup or paddle a boat down the river.
Fixating on a particular toy or the same video or TV show.
Lining up toys, insisting on the same route to the grocery store or requiring family members to sit in the same places.
Hand-flapping, clapping, rocking, pacing, walking on tiptoe, spinning, chewing on clothing or biting hands.
Focusing on a doll's eyes or the spinning wheels of a car, or the smell of an object.