Autism is one of five pervasive developmental disorders (PDD), that are usually evident by the age of three. The term "pervasive developmental disorders" was first used in the 1980s to describe a class of psychiatric problems. PPDs have the following characteristics in common: impairments in social interaction, imaginative activity, verbal and nonverbal communication skills, and a limited number of interests and activities that tend to be repetitive. All types of PDDs are neurological disorders that share, to some extent, similar symptoms.

Children and adults with autism both benefit from regular psychotherapy. In children with severe autism, research has indicated that non-directive play therapy may enhance and accelerate emotional/social development. The objectives of nondirective play therapy are to help the child become self-aware and self-directed while playing in a therapy setting. The play experience is considered therapeutic because it provides a secure relationship between the child and the therapist, so that the child has the freedom to express himself in his own terms, exactly as he is at that moment in his own way and in his own time. This therapeutic approach has also been termed client-centered play therapy and, most recently, child-centered play therapy.

Other types of psychotherapy can be useful in treating autism. Studies have also indicated that family therapy - that is, psychotherapy with the entire family present - can also be helpful in treating autism. Behavioral modification therapy can help parents learn how to appropriately manage a child with severe impairment.

One of the foremost authorities on autism is Tony Attwood, a psychologist and author of several books on asperger's syndrome. According to Attwood, "Long term psychotherapy can help the person with Asperger's syndrome understand key events in his or her life, and cope in a world that does not always understand the perspective and intentions of someone with Asperger's syndrome."

Attwood emphasizes that an effective psychotherapy intervention for autism should include three basic concepts as they pertain to Asperger's syndrome:

1. Theory of Mind
2. Executive Function
3. Weak Control Adherence

"Executive Function" is a term used to describe a set of mental processes that helps us connect past experience with present action. We use executive function when we perform such activities as planning, organizing, strategizing and paying attention to and remembering details. Those with executive function problems, such as many autistic people, have difficulty with planning, organizing and managing time and space. They also show weakness with working memory and objectivity, which is an important tool in guiding one's actions.

The weak central coherence hypothesis of autism was formulated in the last decade. Drawing upon assumptions from gestalt psychology, this hypothesis posits that autism involves a failure of the built-in propensity in normal human information processing to create coherence over a range of stimuli and to generalize over as wide a range of contexts. In people with autism, this failure results from a predominantly piecemeal processing style in which they perceive complex stimuli as a disparate collection of parts rather than as meaningful wholes.

For a psychotherapist to be effective in treating autistic patients, the therapist must have a thorough knowledge of the neuropsychological theories and the complex and diverse behavioral manifestations of autism in terms of their underlying psychological mechanisms.