Abundance Of Theories
The precise cause of autism is not known and many theories have emerged concerning its origin. Initially autism was believed to be caused by destructive parents. Kanner observed in 1943 that there are few "really warmhearted fathers and mothers" among parents of autistic children (Groden 1988). Other experts suggested that parents of autistic children are more likely to be cold and unsupportive of their children than parents of normal children. In the 1950s and 1960s it was still generally believed that this parental behavior caused autism. Children were therefore advised to have psychotherapy for autism. This therapy was generally unsuccessful. Some experts suggested that autistic children be removed from their parents.
In the mid-1960s experts began to challenge the assumption that parents cause autism. Evidence emerged that while autistic children look normal they have particular physical abnormalities. These include a higher-than-normal likelihood of epilepsy—it occurs in as many as 30% of children with autism. Researchers also looked at the way parents interacted with autistic children. Their findings showed that parents of autistic children are equally as skilled as parents of normal children on average.
The general belief today is that autism is a biological disorder and has nothing to do with parenting skill. Clues to what causes autism include a wealth of abnormalities documented to occur in higher percentages among autistic people than normal people. These include certain genetic conditions, epilepsy, mental disabilities, and some birth defects.
Genetics appears to play a role in autism but its role is not completely understood. Brothers or sisters of individuals with autism are slightly more likely than others to be autistic. Approximately 2–3% of siblings of autistic people have the disorder. The twin of an autistic individual is also more likely to have autism.
The occurrence of fragile X syndrome, a genetic disorder, in about 10% of autistic people has presented researchers with a documented cause of the disorder. Fragile X victims have a gap on their X chromosome. The condition is generally linked to mental disabilities and a characteristic facial appearance (a high forehead and long ears) among other traits. Brothers or sisters of individuals with fragile X syndrome are nearly 50% more likely to be autistic than are brothers and sisters of normal children. It is not clear what causes the syndrome.
Another genetic trait more common among autistic individuals than others is neurofibromatosis, a genetic condition which affects the skin and the nerves and sometimes causes brain damage. Researchers also have noted that mothers of autistic children are more likely to receive medication during pregnancy. They have also found that autistic children are more likely to have been born with meconium (the first stool of the infant) in the amniotic fluid during labor. However these events also commonly occur among normal children. Other possible causes of autism include rubella infection in early pregnancy, herpes encephalitis (which can cause inflammation of the brain), and cytomegalovirus infection.
Whatever the cause of the damage, various abnormalities in the autistic brain have been documented. These include variations in the frontal lobes of the brain which focus on control and planning, and in the limbic system. The limbic system is a group of structures in the brain which are linked to emotion, behavior, smell, and other functions. Autistic individuals may suffer from a limited development of the limbic system. This would explain some of the difficulties faced by autistic individuals in processing information.
Studies using MRI (magnetic resonance imaging) scanners have found abnormalities in the cerebellum. Some researchers suggest that the section where abnormalities have been documented is the part of the brain concerned with attention. Other tests using electroencephalograms have found that autistic children show abnormalities in the way the brain processes sound.