Autism is one of the mental, emotional, and behavior disorders that appears in early childhood. Autism, or autistic disorder, almost always develops within the first 3 years of a child’s life. Children and adolescents with autism cannot interact normally with other people. Autism thus affects many aspects of their development. Children with and adolescents with autism typically: -have a difficult time communicating with others -exhibit very repetitious behaviors (like rocking back and forth, head banging, or touching or twirling objects); -have a limited range of interests and activities; and -may became upset at a small change in their environment or daily routine. Although symptoms of autistic disorder sometimes can be seen in early infancy, the condition can appear after months of normal development. In most cases, it is not possible to identify any specific event that triggers autistic disorder. About 7 in every 10 children and adolescents with autistic disorder also have mental retardation or other problems with their brain function or structure.
Recent studies estimate that as many as 14 children out of 10,000 may have autism or a related condition. About 125,000 Americans are affected by these disorders, and nearly 4,000 families across the country have two or more children with autism. Three times as many boys as girls have autism. Researchers are still unsure about what causes autism. Several studies suggest that autistic disorder might be caused by a combination of biological factors, including exposure to a virus before birth, a problem with the immune system, or genetics. Scientists also have identified chemicals in the brain and the immune system that may be involved in autistic disorder. As a normal brain develops, the level of serotonin, a chemical found in the brain, declines. In some children with autistic disorder, however, the serotonin levels do not decline. Now researchers are trying to determine whether this happens only to children with autism and why, and whether other factors are involved.