Most parents of autistic children suspect that something is wrong by the time the child is 18 months old and seek help by the time the child is 2 (though the diagnosis is usually not made until long after that). Children with autism typically have difficulties in verbal and nonverbal communication, social interactions, and pretend play. In some, aggression -- toward others or self -- may be present.

Some children with autism appear normal before age 1 or 2 and then suddenly "regress" and lose language or social skills they had previously gained. This is called the regressive type of autism.

People with autism may perform repeated body movements, show unusual attachments to objects or have unusual distress when routines are changed. Individuals may also experience sensitivities in the senses of sight, hearing, touch, smell, or taste. Such children, for example, will refuse to wear "itchy" clothes and become unduly distressed if forced because of the sensitivity of their skin. Some combination of the following areas may be affected in varying degrees:

• Communication
  • Is unable to start or sustain a conversation
  • Develops language slowly or not at all
  • Repeats words
  • Reverses pronouns
  • Uses nonsense rhyming
  • Communicates with gestures instead of words
  • Has a short attention span
• Social interaction
  • Shows a lack of empathy (can't understand that other people feel differently or know different things)
  • Has difficulty making friends
  • Is withdrawn
  • Prefers to spend time alone rather than with others
  • Is less responsive eye contact or smiles
• Response to sensory information
  • Has heightened or diminished senses of sight, hearing, touch, smell, or taste
  • Seems to have a heightened or diminished response to pain
  • May withdraw from physical contact because it is overstimulating or overwhelming
  • Does not startle at loud noises
  • Rubs surfaces or mouths objects
• Play
  • Shows little pretend or imaginative play
  • Doesn't imitate the actions of others
  • Prefers solitary or ritualistic play
• Behaviors
  • Uses repetitive body movements
  • Shows a strong need for sameness
  • "Acts out" with intense tantrums
  • Has very narrow interests
  • Demonstrates perseveration (an obsessive interest in a single item, idea, activity, or person)
  • Displays an apparent lack of common sense
  • Shows aggression to others or self
  • Is overactive or is very passive

Routine developmental screening should be performed for all children at all well-child visits to their pediatrician. Further evaluation is warranted if there is concern on the part of the clinician or the parents. This is particularly true whenever a child fails to meet any of the following language milestones:

• Babbling by 12 months
• Gesturing (pointing, waving bye-bye) by 12 months
• Single words by 16 months
• Two-word spontaneous phrases by 24 months (not just echoing)
• Loss of any language or social skills at any age.

These children might receive an audiologic evaluation, a blood lead test, and a screening test for autism such as the Checklist for Autism in Toddlers (CHAT) or the Autism Screening Questionnaire.

A clinician experienced in the diagnosis and treatment of autism is usually necessary for the actual diagnosis.

DIAGNOSTIC CRITERIA FOR AUTISTIC DISORDER

Because there is no biological test for autism, the diagnosis will often be based on specific criteria laid out as A, B, and C in the Diagnostic and Statistical Manual IV, as follows.

A. A total of six or more items from (1), (2), and (3), with at least two from (1) and one each from (2) and (3): :

1. Qualitative impairment in social interaction, manifest by at least two of the following:
   • Marked impairment in the use of multiple nonverbal behaviors, such as eye-to-eye gaze, facial expression, body postures and gestures, to regulate social interaction
   • Failure to develop peer relationships appropriate to developmental level
   • Lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g., by lack of showing, bringing, or pointing out objects of interest)
   • Lack of social or emotional reciprocity
2. Qualitative impairment in communication, as manifest by at least one of the following:
   • Delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)
   • In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
   • Stereotyped and repetitive use of language, or idiosyncratic languag
   • Lack of varied, spontaneous make-believe, or social imitative play appropriate to developmental level
3. Restrictive repetitive and stereotypic patterns of behavior, interests, and activities, as manifested by at least one of the following:
   • Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus
   • Apparently inflexible adherence to specific nonfunctional routines or rituals
   • Stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)
   • Persistent preoccupation with parts of objects.

1. Social interaction
2. Language as used in social communication
3. Symbolic or imaginative play

DIAGNOSTIC EVALUATION

The other pervasive developmental disorders include:

• Aspergers syndrome
• Rett syndrome
• Childhood disintegrative disorder
• Pervasive developmental disorder - not otherwise specified (PDD-NOS), also called atypical autism.

The diagnostic evaluation of autism will often include a complete physical and neurologic examination, as well as the use of a specific diagnostic instrument such as the Gilliam Autism Rating Scale, the Pervasive Developmental Disorders Screening Test-Stage 3, the Childhood Autism Rating Scale (CARS), or the Autism Diagnostic Observation Schedule-Generic. Children with known or suspected autism will often have genetic testing (looking for chromosome abnormalities) and perhaps metabolic testing.

Because autism encompasses such a broad spectrum, a brief observation in a single setting cannot predict an individual's true abilities. Ideally, a multidisciplinary team will evaluate the child. This evaluation might include a comprehensive speech-language-communication evaluation, a cognitive and adaptive behavior evaluation, a sensorimotor and occupational therapy evaluation, and neuropsychological, behavioral and academic assessments.

Sometimes people are reluctant to make the diagnosis of autism because of concerns about labeling the child. Although pigeonholing in a way that suggests limits is inappropriate due to the wide range of autistic spectrum conditions, failure to make a diagnosis can lead to failure to get the treatment and services the child needs.