Cause of Autism Part II
Etiology Theories for Physical Disorder Models
While the etiology of autism is still largely unknown, however there are no shortage of theories in the area. In part, the mystery what could be the cause of autism has been slow to resolve due to its relatively recent identification as a disorder, and because government funding of autism research still is far behind that of less common disorders. What funding which has been made available, has for the most part been directed toward epidemiological research, rather than towards clinical studies which are investigating possibilities of environmental triggers. Since the 1970s there has been a dramatic increase in the recorded incidences of autism.
Autism is known to be a highly inheritable disorder. Research which has been done by some institutions, seeks to find a way for the earlier, and more accurate detection of autism, much like that done for Rett Syndrome. Instead of searching for only one gene as the cause for autism, many of these studies are searching for complex interactions between a varied number of genes.
A 2005 study done by the Duke Center for Human Genetics at Duke University finds some evidence that complex interactions between GABA (gamma aminobutyric acid) receptor genes might be part of the cause of autism. One of the functions of the GABA genes is to inhibit the nerve system from firing. The theory is that somehow GABA genes suffer damage of some kind, leading to an overwhelmed sensory system which then causes the uniqe characteristics of autism.
Brain Testosterone Theory
Simon Baron-Cohen has proposed a model for autism based in his empathising-systemising theory. His team at the Autism Research Centre in Cambridge, UK, measured testosterone levels in the amniotic fluid of mothers while pregnant. This was presumed to reflect levels in the babies themselves. The team found that the babies with higher fetal testosterone levels had a smaller vocabulary and made eye contact less often when they were a year old.
His group has looked at the original 58 children again, at age four. The researchers found that the children with higher testosterone in the womb are less developed socially, and the interests of boys are more restricted than girls. The results are published in the Journal of Child Psychology and Psychiatry in a 2004 issue.
Baron-Cohen theorizes that high fetal testosterone levels push brain development towards an improved ability to see patterns and analyze complex systems. Males supposedly tend to be better at such spacial tasks than females. But the high levels are thought to inhibit the development of communication and empathy. (New Scientist, May 24, 2003).
In 2004 Dr. Geier and his son, David Geier published a paper in the journal Medical Hypotheses on the potential importance of lowering testosterone as part of the treatment of autistic spectum disorders, which they claim involve mercury toxicity. In 2006 the Geiers published in the peer-reviewed Hormone Research journal, a paper titled "A Clinical and Laboratory Evaluation of Methionine Cycle-Transsulfuration and Androgen Pathway Markers in Children with Autistic Disorders." This paper presented data from Geier's clinic, suggesting a cyclical interaction between the methionine cycle-transsulfuration and androgen pathways in children with autistic disorders.
Children exhibiting behavioral and learning disorders may do so in part because of diets deficient in vital nutrients needed for their brains to function and develop normally.
In 1998, a small study published in the medical journal Lancet found a consistent set of bowel disorders among a dozen autistic children. Although an emphasis was placed by the authors on a possible link to the MMR vaccine, the study also suggested nutritional deficits caused by bowel disorders may have contributed to the onset of neurological disorders. It should be noted that the sample was very small, and the results have not been replicated by other researchers.
Leaky Gut Syndrome and Related
Some children with autism are said to have responded well to dietary intervention such as eliminating gluten (a protein found in most grains) and casein (the protein found in milk) as well as phenyls and food coloring (see Feingold diet). Most data regarding the validity of these interventions have been the subjective observations of parents and caretakers and no scientific study with proper subject elimination has taken place.
Some of the possible determining factors regarding the effectiveness of this as a treatment involve coincidence of a combination of asthma, eczema, strange "yeasty" diaper rash, diarrhea and constipation, and abnormal eating habits.
Several unproven theories behind the effectiveness of this as a treatment involve damage to the lining of the stomach and/or intestines allowing the proteins to be improperly metabolized as glutomorphine and casomorphine which are both opiates. The damage to the gut lining is theorized to be caused by immunio-abnormalities and possibly the incidence of early oral-antibiotic use combined with a genetic predisposition. However, this is speculation and there is as yet no proof.
Increased intake of folic acid by pregnant women roughly coincides with the reported increase in the prevalence of autism. The explanation offered is that folic acid allows more brain cells to survive than should. This hypothesis is still untested at this point.
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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