Cause of Autism Part IV
Brain trauma and Autism
Susan Bryson has claimed that some autistics have evidence of trauma to the brain stem in early development, and that a small portion of the thalidomide victims have become autistic and therefore could be a cause of autism. The victims' limbs were normal unless thalidomide use continued later in the pregnancy. The brain stem anomaly's most striking feature is inability to focus attention away from a stimulus in a short time like neurotypicals, as demonstrated in a psychological test.
Some people claim the inability to shift attention quickly interferes with the ability to read nonverbal language where fast attention shifts are needed (such as eye language), suggesting that being nonverbal is not a primary feature of autism. Strong and shiftless focus is, however, a benefit in some areas like science, programming, and advanced mathematics. This is supported by the monotropism hypothesis.
Dr. Bernard Rimland's influential research and his book Infantile Autism (1967) argued that autism was not caused by childhood trauma or abuse, but by damage to certain areas of the brain, particularly the reticular formation which associates present sensory input with memories of past experiences. Dr. Rimland is a foremost advocate of the theory that autism may be precipitated by mercury and heavy metal toxicity. He is also prominent in claims of successful treatment of autism in children — particularly regarding improvements in ability to comprehend the spoken word— with the gluten-free, casein-free diet and mercury chelation therapy.
Others suggest Dr. Bernard Rimland's methods alleviate the symptoms of heavy metal poisoning, but not autism. Curing heavy metal poisoning when it is present is a worthy goal (it helps with IQ and other learning difficulties as well as general health), but claiming a benefit for autism is a misrepresentation. Heavy metal poisoning may be more common among autistics due to a severe metallothionein deficiency, but more evidence is needed to substantiate the idea that heavy metals cause autism. It is still being studied. The presence of heavy metals (e.g.: detected through simple hair-sample analysis), particularly mercury, might make an autism diagnosis more likely, however.
A large-scale study in Sweden found that ultrasound scanning during pregnancy very significantly increased the number of male babies born who would become left-handed children. This suggests that the male brain may be especially vulnerable to small amounts of ultrasound heating while in the womb. Research is ongoing, and there is as yet no proven or disproven link betweent ultrasound scans and subsequent development of autism spectrum disorders, but a possible casual link has been widely suggested.
Viral or Bacterial Infection and Autism
A growing body of peer-reviewed studies published in mainstream journals has shown that many common diseases of previously unknown origin are caused by the presence of slowly acting viruses. For example, cervical cancer is caused by the human papilloma virus; some cases of liver cancer are caused by hepatitis C or B; it has even been suggested that schizophrenia may be caused by Borna virus, although some recent evidence weighs against this. Paul W. Ewald, among others, argues that the available data on the origin of autism is consistent with the possibility that it is being caused by a virus or infection.
Alternatively, it was hypothesized that use of certain antibiotics, rather than the initial infection which they cure, may be associated with autism; that is, depending on certain conditions they could be either harmful or helpful.
Immune disorders and immune system insults
An increasing number of studies in national journals are linking the regulation of the immune system with nervous system diseases such as multiple sclerosis and even Alzheimer's disease. Cognitive function, memory, and fatigue may all be controlled by small molecule immune modulators. "Current treatments need to be modified, if we confirm that this finding applies to children with autism," said Dr. Jeffrey Galpin, a professor at USC and an infectious disease specialist. However, there is no evidence yet that it does apply to autistic people.
Blood Type Theory and Autism
D'Adamo and Whitney (104-105) report that maternal rubella infection is thought to play a role in some cases of Asperger's Syndrome. However, no relationship between AS and reactions to vaccines and other external factors has been proven.
D'Adamo and Whitney (104-105) report that although there is not a published study , an informal accounting shows a marked prevalence of blood type A among Asperger's Syndrome children. The other blood types have low incidence, risk or severity of Asperger's Syndrome and Autism. Since the type A limits several dietary lectins that are thought to interfere with secretin, it is not too far-fetched to consider that improvement in these children may have actually resulted from enhancement of their own secretin metabolism.
A study by Horvath et. al (1998) on secretin and Asperger's reported that children with Asperger's Syndrome or Autism and gastrointestinal problems had improved gastrointestinal function after secretin infusion and that the children become more sociable and communicative. They also benefited with a low lectin and wheat diet. This suggest that there might be a gastrointestinal and diet cause of Asperger's or Autism. However, there was no control group of normal children who had the same treatment. (See also: QuackWatch: Secretin.
Amygdala neurons and fear theory
Two preliminary studies have linked lower neuron density in the amygdala with autism. It is not clear at this time whether this could be a cause or an effect of the condition. It is postulated that this physical difference may directly lead to symptoms like increased anxiety and nervousness, and indirectly (through some unknown mechanism) to poor social skills.
These are only some of the major theories on the factors which may contribute to the development of autism.
For more information about autism and the autistic community be sure to check out the resources available at answers-about-autism.
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