Because young infants are so limited in their range of behavior, autistic disorders are generally discovered gradually, and rarely diagnosed before the age of two or three. Parents may not realize that their baby's behavior is different from that of other infants until he or she reaches an age where a wide range of behaviors are typically displayed. Most doctors may attempt to reassure concerned parents of infants under two years that their children are "normal," or will "grow out of" a disturbing behavior, because many children do. At the time that speech and language usually develop, parents are more likely to observe that their autistic child is not at the same level as other children his age. Once the child is old enough to play with other children, it becomes more apparent that the autistic child either isn't interested in doing so, or does so in strange, unusual ways that differ from most children of the same age. Motor development may also appear unusual, with repetitive motions such as spinning, self-injurious behaviors such as headbanging, and rocking back and forth, giving the parents strong clues that their child behaves differently from others.
The child who continues to display unusual behaviors at about the age of two years would most likely receive a referral from the pediatrician to a child psychiatrist or to an early intervention program with a multi-disciplinary staff including psychiatrists, psychologists, and social workers. These professionals would be the ones to diagnose autistic disorder, and, ideally, offer an early intervention program simultaneously. In order to reach the diagnosis, the professional(s) would observe the child both with and without parents present, interview the parents about the pregnancy, birth, siblings, family history, and early behaviors, and an assessment like the Bayley Scales of Infant Development might be administered.
Differential diagnosis is the process of distinguishing one disorder from other similar disorders. Because there are currently no medical tests (such as a blood test) to detect autism, the diagnosis is often established by ruling out other disorders.
mental retardation. It is estimated that approximately 40% to 60% of children with autistic disorders show some degree of mental retardation ranging from mild to profound. It is possible for a child to have both conditions. What distinguishes children with mental retardation who do not have autistic symptoms from those who do is evenness of development. Children with mental retardation tend to exhibit a more even level of functioning in all areas, whereas autistic children tend to exhibit extreme variability within areas and between areas. Children with autistic disorders show uneven development in areas such as motor, language, and social skills. A child with autism may have high-level cognitive functioning in one area, but low-level cognitive functioning in another area, for example. Or a child with autism may exhibit delayed cognitive development, but normal motor skills development. For this reason, autism is often referred to as a "spectrum disorder" because of the large spectrum or range of variability in symptoms and functioning. Also, many children with mental retardation relate well to people and enjoy social connection, which is rare for autistic children.
language disorder. Children with autistic disorders may appear similar in some ways to children with language disorders. Unlike autistic children, however, children with language disorders have normal responses to most people, situations, and objects. They make eye contact and show interest in peer and adult relationships.
childhood schizophrenia. Schizophrenia is a disturbance of emotion and thought processes that rarely occurs in young children. When it does, it is characterized by hallucinations and delusions— seeing and hearing things that are not there, for example. These are not symptoms that appear among autistic children.
degenerative organic brain disorder. This is an extremely rare condition that may at first appear similar to autistic disorders. In degenerative organic brain disorder, the child begins to develop normally. But over time, speech, language, motor skills and other age-appropriate behaviors disintegrate and do not return. The disintegration is progressive. In children with autistic disorders, some children may begin to develop words and language and then lose them at around eighteen months. However, with appropriate education, these skills can be relearned and surpassed by the autistic child.
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Autism is a developmental disorder that manifests itself in early childhood and affects the functioning of the brain, primarily in the areas of social interaction and communication. Children with autism look like other children but do not play or behave like other children. They must struggle daily to cope and connect with the world around them.