INTRODUCTION
Autism is a disorder of neural development characterized by impaired social interaction, verbal and non-verbal communication, and by restricted and repetitive behavior. The diagnostic criteria require that symptoms become apparent before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize; how this occurs is not well understood. It is one of three recognized disorders in the autism spectrum (ASDs), the other two being Asperger syndrome, which lacks delays in cognitive development and language, and pervasive developmental disorder, not otherwise specified (commonly abbreviated as PDD-NOS), which is diagnosed when the full set of criteria for autism or Asperger syndrome are not met.
CAUSES OF AUTISM
The causes of autism remain a major area of research and of controversy. Studies indicate that autism is often associated with abnormalities in the functioning of the brain and that the disorder may have a genetic basis in most cases.
Causes before Birth
The causes of autism before birth includes:
Genetic causes: Studies of identical and fraternal twins have demonstrated that genetic factors are the largest cause of autism If one identical twin is diagnosed with autism, the other identical twin will also be diagnosed with autism 60 percent of the time, and with symptoms of an autism spectrum disorder more than 90 percent of the time. This pattern of genetic risk predicts that variation in more than one gene is necessary to cause risk of autism. This does not rule out environmental causes but points to genetics as the primary cause. Additionally, change in the methods of autism diagnosis or in the frequency of autism in the population would lead to a change in the estimate of genetic risk.
Causes of Autism during Birth
Infection and Drugs: Children born to mothers who were infected with certain illnesses or took particular drugs during pregnancy may...