Causes of Autism
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Any research paper on the cause of autism will clearly show that the exact cause of autism is unknown.However, research suggests that it probably has an organic origin, and there seems to be a genetic factor involved. This is supported by case history which reveal that if one of a set of monozygotic twins has autism, the other is likely to develop it also. But due to the greatly varying severity of symptoms, it may be difficult to establish a genetic link. It is also possible that autism is the result of any number of genetic disorders. Research demonstrates that individuals with autism are more likely to suffer from fragile X syndrome, phenylketonuria (PKU) and tuberous sclerosis. While these studies are correlational and, therefore, do not necessarily imply cause-and-effect associations between the various anomalies and autism, they do lend support to the theory of genetic linking.
Neurological Abnormalities
Another possible source for autism is that it may be the result of neurological abnormalities. One study indicates that individuals with autism have a smaller number of Pukinje cells and a smaller number of cells in lobes VI and VII of the brain. Additional studies suggest that autism may be caused by lesions in the medial temporal lobe of the brain. Monkeys with such lesions show symptoms characteristic of autism in that they appear withdrawn and lack eye contact. Autopsies of people with autism reveal a decrease in brain cells in the limbic region, thus supporting the hypothesis of brain lesion etiology. Other research that malformations of the cerebral cortex, particularly in the parietal lobe, may cause autism. Individuals who have had strokes in this area of the brain often develop autistic-like symptoms, such as a blank stare.
Causes of Autism Identified by Scientific Research
Several possible causes of autism have been identified by scientific research.
- Genetics
- Fragile X Syndrome
- Growth Dysregulation Hypothesis
One cause that is association with having this disorder is genetics. Several studies have indicted that children with autism often comes from families with disorders such as bipolor disorder. The exact relation is not completely known. However, some researchers hypothesis that perhaps the same genetic link exists between bipolor disorder and autism.
In addition, a condition known as fragile X syndrome exists in about two to five percent of autistic children. This syndrome occurs when the X chromosome of the child appears to be pinched when viewed under a microscope. Children with autism who have this have a form of mental retardation. Parents who have a child with autism who also has fragile X syndrome have about a 50% of having a boy, if they have additional children, who will have the same condition.
In relation to a genetic or biological cause, other studies have indicated that autism is related to abnormal brain development in infants. The theory, known as Growth Dysregulation Hypothesis, points to problems with biological development of the brain. If the brain does not develop normally in the first few months of birth, then some autism may be more likely to occur.
However, with these individual theories and ideas about the causes of autism, it is important to note that one specific cause does not explain all cases of autism. Rapin explains that "while autism is a specific behavioral syndrome it is not a disease or a condition with a single etiology. Its etiology is unknown in the vast majority of cases".
Finally, it is important to note that one commonly thought cause of autism is completely incorrect. A theory suggests that a preservative containing mercury that is used in the measles-mumps-rubella (MMR) vaccine was related to autism. Recent studies have shown that this preservative is not linked to a child acquiring autism. In addition, mercury is no longer used in vaccines for children.