Increasingly, evidence from neurologic research is pointing to the fact that autism is inherited, and that children with autism have abnormalities in brain architecture that start before birth.
What is autism?
Classically, autism is a disease of the brain that manifests symptoms before a child is three years old.
The child has difficulty with both verbal and non-verbal types of communication. For example, the child may have prolonged delays in developing meaningful verbal communication. He also has problems interacting with other people. He may have difficulty forming meaningful relationships with others. These children can also display repetitive (stereotyped) behaviors.
Recently, autism has been expanded to include some other closely associated psychological/neurodevelopmental disorders, like Asperger’s syndrome. Autism is now more properly referred to as Autism Spectrum Disorder (ASD).
What causes autism?
Research hasn’t shown one single cause of autism. There are several factors that may contribute to a child developing autism.
Genetics seems to play a large role. Siblings of autistic children may have as much as a 30-times greater risk of developing autism as other children in the general population. Also, there is a much higher rate of autism occurring in monozygotic twins (twins who developed from a single fertilized egg) than in dizygotic twins (twins who developed from two eggs.) Though there doesn’t seem to be a single gene that codes for autism. Autism may come about from the interaction of several genes.
There are also other risk factors that seem to predispose children to developing autism. There is a higher incidence of autistic children in children who have “older” parents (over about age 30), mothers who develop diabetes while pregnant, meconium in the amniotic fluid, some maternal medications and, possibly some other factors.
No good evidence that vaccinations cause autism
There is no good evidence from reputable researchers published in peer-reviewed scientific journals that vaccinations, or thimerosal (a mercury derivative that used to be found in vaccines in small quantities) causes autism.
Claims that vaccines or their components caused autism date back to the 1990s. During that period, Andrew Wakefield, a British physician, deliberately falsified data to make it appear that vaccines were responsible for the development of autism. The original paper was retracted, the data repudiated and Wakefield lost his medical license for the fraud. But his research sparked the anti-vaccine movement.
Some parents, religious sects, naturopaths, chiropractors and others worked to publicize Wakefield’s false data. They pushed to be allowed to not vaccinate their children. As the movement spread, more children remained unvaccinated. Gradually, diseases that were preventable by vaccination (measles, pertussis and others) began to increase in the US and elsewhere.
What happened with the anti-vaccine movement is similar to what happened with the now-debunked Regnerus study on gay parenting. The data was manipulated to produce the desired result. Those people who are against gay parenting took it and ran with it, publicizing it wildly world-wide (in fact, as John and Becca have written before – they were the people behind the study in the first place).
In spite of evidence to the contrary, Regnerus’ university and department rejecting his conclusions, and the denunciation by the American Sociological Society and others, those who oppose gay parenting continue to use false data to achieve their ends. The anti-vaccine groups do the same. In spite of strong evidence to the contrary, they have fixated on their beliefs that vaccines are the cause of autism, and refuse to change their minds in spite of, and not because of, the science.
Increasing evidence of structural brain abnormalities
There is increasing evidence that children with autism have structural brain abnormalities.
Two studies show increase in brain volume in autistic children. One notes increase in head circumference in these babies. The other notes similar results based on MRI studies of the children’s heads. They say that there may be an overgrowth of some cell types in the cortex and that this may lead to autism.
A more recent study shows similar results on a microscopic level. The neurons of the cortex are arranged in layers. In autistic children, these layers are disrupted. There is a disarray in the structure of the cortical cells. This can be seen in specially stained photomicrographs. The brain tissue was taken at autopsy from autistic children who died and were between the ages of 2 and 15.
For these cortical layers to be disordered, the process probably started months before the autistic baby was born. The disorganization starting as the fetal brain was early in development. More from NIH:
“While autism is generally considered a developmental brain disorder, research has not identified a consistent or causative lesion,” said Thomas R. Insel, M.D., director of NIMH. “If this new report of disorganized architecture in the brains of some children with autism is replicated, we can presume this reflects a process occurring long before birth. This reinforces the importance of early identification and intervention.”
Here’s a short video showing the brains of children with autism:
So, more evidence is accruing that autism has a strong genetic component, may be influenced by other physical factors (as listed above) and starts in the prenatal period. While evidence that it is caused by vaccinations, or any components thereof, continues to be completely lacking.