Demographics

Demographics

Autism is a disorder that affects predominantly males (four times as many males as females have autism). According to studies, autism is increasing in the pediatric population. In 1966, 4–5 babies per 10,000 births developed autism, while in 2003, two studies showed that between 14–39 babies per 10,000 develop the disorder. Although there is no question that more clinical cases are being detected, the increase in prevalence of autism is in dispute as diagnostic practices have changed over the years and this heightened awareness has changed the evaluation of previously unrecognized cases.

Causes and symptoms

Although autism is behaviorally defined, it is now well recognized to be the endpoint of several organic causes. These include prenatal problems such as rubella (measles) infection, untreated metabolic disorders, and anticonvulsant medication taken during pregnancy, as well as postnatal infections such as encephalitis. A specific medical cause is found in only a minority of people with autism (6–10%, depending on the study). Epilepsy occurs more commonly than usual in patients with this disorder and was one of the early indications that this was a neurobiological problem and not one caused by parental behavior or the environment.

In most people with autism, genetic factors play a key role. Multiple genes are likely to be involved, and studies have identified possible candidate genes on chromosomes 2, 7, 16, and 19. Autism has been associated with some genetic abnormalities, especially on chromosome 15, and it is also found associated with the "fragile X syndrome." Despite the fact autism is now agreed to be a neurobiological disorder, results from structural brain scans have not shown consistent features that point to a diagnosis of autism.

Symptoms of autism usually appear during the first three years of childhood and continue throughout life. Some common symptoms are:

• absence or impairment of imaginative and social play
• impaired ability to make friends with peers
• impaired ability to initiate or sustain a conversation with others
• stereotyped, repetitive, or unusual use of language
• restricted patterns of interests that are abnormal in intensity or focus
• apparently inflexible adherence to specific routines or rituals
• preoccupation with parts of objects

Children with some symptoms of autism, but not a sufficient number to be diagnosed with the classical form of the disorder, often receive the diagnosis of pervasive developmental disorder, not otherwise specified (PDDNOS). People with autistic behavior, but also have well-developed language skills, are often diagnosed with Asperger syndrome. Children who appear normal in their first several years, then lose skills and begin showing autistic behavior, may be diagnosed with childhood disintegrative disorder (CDD). Girls with Rett syndrome-linked genetic disorder characterized by inadequate brain growth, seizures, and other neurological problems, may also show autistic behavior. PDD-NOS, Asperger syndrome, CDD, and Rett syndrome are referred to as autism spectrum disorders.