Not until the middle of the twentieth century was there a name for a disorder that now appears to affect an estimated 3.4 every 1,000 children ages 3-10, a disorder that causes disruption in families and unfulfilled lives for many children. In 1943 Dr. Leo Kanner of the Johns Hopkins Hospital studied a group of 11 children and introduced the label early infantile autism into the English language. At the same time a German scientist, Dr. Hans Asperger, described a milder form of the disorder that became known as Asperger syndrome. Thus these two disorders were described and are today listed in the Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR (fourth edition, text revision) as two of the five pervasive developmental disorders (PDD), more often referred to today as autism spectrum disorders (ASD). All these disorders are characterized by varying degrees of impairment in communication skills, social interactions, and restricted, repetitive and stereotyped patterns of behavior.
The autism spectrum disorders can often be reliably detected by the age of 3 years, and in some cases as early as 18 months. Studies suggest that many children eventually may be accurately identified by the age of 1 year or even younger. The appearance of any of the warning signs of ASD is reason to have a child evaluated by a professional specializing in these disorders.
Parents are usually the first to notice unusual behaviors in their child. In some cases, the baby seemed "different" from birth, unresponsive to people or focusing intently on one item for long periods of time. The first signs of an ASD can also appear in children who seem to have been developing normally. When an engaging, babbling toddler suddenly becomes silent, withdrawn, self-abusive, or indifferent to social overtures, something is wrong. Research has shown that parents are usually correct about noticing developmental problems, although they may not realize the specific nature or degree of the problem.
The pervasive developmental disorders, or autism spectrum disorders, range from a severe form, called autistic disorder, to a milder form, Asperger syndrome. If a child has symptoms of either of these disorders, but does not meet the specific criteria for either, the diagnosis is called pervasive developmental disorder not otherwise specified (PDD-NOS). Other rare, very severe disorders that are included in the autism spectrum disorders are Rett syndrome and childhood disintegrative disorder.
Autism is classified as a neurodevelopmental disorder that manifests in delays of "social interaction, language as used in social communication, or symbolic or imaginative play," with "onset prior to age 3 years," according to the Diagnostic and Statistical Manual of Mental Disorders. The ICD-10 also requires symptoms to "manifest before the age of three years." Autism is often not physiologically obvious, in that outward appearance may not indicate a disorder, and diagnosis typically comes from a complete physical and neurological evaluation.
There have been large increases in diagnosed autism, for reasons that are heavily debated by researchers in psychology and related fields within the scientific community. Some believe this increase is largely due to changed diagnostic criteria and/or societal factors, while others think the reason is environmental. The United States Centers for Disease Control (CDC) estimate the prevalence of autism spectrum disorders to be between one out of every 500 to one out of every 166 births. The National Institute of Mental Health (NIMH) states the "best conservative estimate" as 1 in 1000.
Although the specific causes of autism are unknown, there is a large database of links between autism and genetic loci that span every chromosome. Further, observations and studies that autistic children have generally larger head circumference are intriguing, but their roles in the disorder are unclear. One group of researchers claims to have found a link between autism, abnormal blood vessel function, and oxidative stress, with potential for new medical therapies should this line of evidence prove fruitful.
With early intervention, intense therapies (most notably Applied Behavioral Analysis), practice, and schooling, some children diagnosed with autism may improve on their skills to the point of neurotypical children. Some autistic children and adults are opposed to attempts to cure autism, because they see autism as part of who they are, and in some cases they perceive attempts of a cure to be intensive and unnatural.