Autism is a developmental disability that can severely impair an individual's ability to communicate and socially interact with others. It is four times more prevalent in males than females. Currently, autism is believed to affect 1 in every 166 people. Although we do not yet know all the reasons why the rate of people being diagnosed with autism has increased substantially over the past two decades This is thought to be due in part to improved diagnostic techniques and to changes in the diagnostic criteria for "autism spectrum disorders".

Classic Autism (also known as Kanner's Autism or Syndrome), Asperger's Syndrome and Pervasive Developmental Disorder (PDD) are specific types of neurobehavioral complications classified within a group of developmental conditions known as "Autism Spectrum Disorders". Autism is considered a spectrum disorder because the number and intensity of the symptoms people with autism display may vary widely. However, all individuals afflicted with autism demonstrate impairments to some degree in the following three areas: communication, social interactions and restricted patterns of behavior. For example:

Social Interaction: A person with an autism spectrum disorder may not use or understand non-verbal communication, or they may not develop peer relationships that are appropriate to their developmental level. Often, there is a noticeable lack of emotional reciprocity (you smile at him but he does not smile back). Adults with autism may appear aloof and indifferent to others; children seem to be wrapped up "in their own world".

Communication: There is a significant delay in, or a total lack of, speech development, with no corresponding attempts to communicate by gestures. An autistic individual may have difficulties in sustaining or initiating conversation or they may repeat parts of their speech over and over again concerning the same topic.

Patterns of Behavior: Restricted, repetitive and stereotyped patterns of behavior, interests and activities are the hallmark of autism. An individual with autism or a related disorder may have an intense preoccupation with one subject area or interest. The affected individual may have nonfunctional, rigid rituals or routines. In children, there is a lack of make-believe or social imitative play. Repetitive motor mannerisms (for example, hand flapping or spinning of objects) may also be present.

Below are some examples of behaviors that are characteristic of Autism Spectrum Disorders. An individual with autism may exhibit a combination of or all of these behaviors, depending on where (s)he falls on the spectrum:

An infant does not imitate other children and/or does not reach out to their parents.
A child does not develop age-appropriate peer relationships and has difficulty interacting with others.
Little or no eye contact, aloof manner, appears detached, lacks spontaneous sharing of interests with others.
Inappropriate attachments to objects, obsessive, odd play (for example, lining up or spinning toys).
Resists changes in routine more than typically expected for a child his/her age.
Eats only certain foods or insists on a preferred texture of clothing.
Repetitive motor movements and/or demonstrates uneven fine and gross motor skills development.
Becomes stiff when held, does not liked to be touched, or is 'floppy' and has low muscle tone.
Does not develop speech or has speech that subsequently deteriorates, does not point or gesture.
Repeats words or phrases over and over again; talks only about narrowly defined topics.
Difficulty in discussing abstract concepts takes everything literally or has impaired language skills.

The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) classifies a developmental condition within the group of Autism Spectrum Disorders as a "temporary episodic clinical disorder." This suggests that symptoms of these disorders vary in intensity and that with proper diagnosis and targeted treatment and rehabilitation, there is a possibility of improvement. The specific diagnoses used for autism and related disorders are:

Autistic Disorder (Classic Autism): Onset occurs before child is 3 years old. The child shows impairment in the three areas of observable symptoms: difficulty in communication, social interaction and repetitive, stereotyped patterns of behavior.

Childhood Disintegrative Disorder: The child develops normally in all areas for the first two years, then shows a significant loss of previously acquired skills.

Rett's Disorder (also known as Rett Syndrome): Found almost exclusively in females, the child achieves normal development for the first five months, then loses previously acquired communication skills and the purposeful use of the hands. These losses are soon followed by other areas of deterioration, including apraxia (loss of ability to control complex muscle movements), gait disturbances and sometimes seizures. This disorder is very rare.

Asperger's Disorder (also known as Asperger's Syndrome): Children with this disorder demonstrate average to above-average intelligence and no significant delay in language but show impairment in social interactions and have a restricted range of interests and activities. These children often can be very talkative, although their speech tends to lack normal fluctuation of tone or prosody. They can speak in a pedantic or lecturing tone.

Pervasive Developmental Disorder, Not Otherwise Specified (Atypical Autism): In the case of "PDD-NOS", there is significant impairment in the three areas described above, but the child does not meet the full criteria for a specific diagnosis.

Testing for Autism Spectrum Disorders
At this time, there is no single diagnostic test that can conclusively prove a child has an autism spectrum disorder. The most important signs to watch for are delays in the development of speech and of reciprocal interactions between the child and his/her caregivers. Parent's intuition is an important yardstick as well. If you feel that there is something wrong with your child's development – trust your intuition. This is because you may be discerning subtle failures in your child's nonverbal communication with you.

There are several screening tools or checklists which can be useful in deciding whether to pursue further diagnostic testing. These include:

CHAT – Checklist for Autism in Toddlers
CARS – Childhood Autism Rating Scale
Autism Screening Questionnaire
Screening Test for Autism in Two-Year Olds
Social Reciprocity Scale

If a child demonstrates elements suggestive of an autism spectrum disorder, then a comprehensive evaluation is indicated. The standard clinical diagnostic tool in the field is the ADOS (Autism Diagnostic Observation Schedule) which is a semi-structured assessment of communication, social interaction, and play or imaginative use of materials.

Other testing also is necessary to rule out other causes of neurological impairment and clarify the diagnosis.

Hearing Tests. The first assumption most parents make when their child has speech problems or does not respond to aural stimuli is that their child may be deaf or hearing impaired. A hearing test can indicate if a child has a hearing impairment. Tests can be performed on children even in infancy; audiologists measure responses such as blinking, staring or turning the head when a sound is presented.
Genetic Testing involves using a blood test to screen for any genetic abnormalities that could cause developmental delays.
Metabolic Screening consists of blood and urine tests to measure how a person is metabolizing food. Problems in this area can significantly impact a child's growth and development resulting in symptoms similar to autism.
Electroencephalograms (EEGs) measure brain waves, and can uncover seizure disorders or other abnormalities.
Head CTs and MRIs are helpful in detecting structural abnormalities. However, because most children with autism do not have structural abnormalities, these tests usually do not demonstrate specific structural abnormalities.
High Definition Brain SPECT Imaging is a method to physiologically map and detail the regions of the brain which are impaired from functioning effectively. Some autism treatment programs are using SPECT scans as part of a battery of tests used in initial assessment and to track a child's improvements.

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