The following article by Dr. Solomon was recently published in The Toledo Blade:
Autism spectrum disorders (ASD), characterized by delays in language, problems with social interaction and dominating, stereotyped behaviors and interests, have been increasing at a dramatic rate of 15% per year every year for the last 20 years! ASDs now affect 1 out of every 88 children, 1 in every 54 boys! This astounding increase in the number of children is unprecedented. No other developmental disability is increasing as quickly. As I travel around the country giving lectures and workshops, the most commonly asked question is ‘Why the increase?’ In this article I will summarize the latest evidence that answers the question.
First, there is no question that genetics plays a role. In the most recent twin study (Hallmayer, 2011) identical twins had a 77% co-occurrence rate and fraternal twins, a 31% (males) to 36% (females) rate. This confirms previous work that has identified dozens of ‘autism genes’ that contribute to ASD. Interestingly, all the genes identified so far code for neuronal connections in the brain. Neurons are the cells that make the brain function. In other words, the fundamental nature of autism is an under-connected brain caused by dysfunctional webs of neurons. A very recent study of hundreds of families done by the Autism Sequencing Collaborative (http://www.reuters.com/article/2012/04/04/autism-usa-genes-idUSL2E8F45FE20120404) reveals yet another genetic mechanism—spontaneous mutation—as a contributor. Spontaneous mutation means that genes in father’s sperm or mother’s eggs can change spontaneously (i.e. these are not the stable inherited ‘autism genes’ mentioned above) to cause autism. Sperm, because of it’s daily production, appears to be the most vulnerable to these mutations.
While genetics has been established as one contributing cause, this same article on twins determined that genetics couldn’t explain everything. In other words, the environment is also implicated. In fact mathematical modeling suggested that only 38% of the cases could be attributed to genetic factors compared with the 90% suggested by previous studies.
As an example of environmental risk, a recent article (Coyle, 2011) found an elevated risk of autism in children whose mothers took antidepressants during the year before delivery. Another article on environmental risk (Engel, 2011) found that prenatal exposure to organophosphate pesticides reduced IQ in tested children. Other environmental factors that have been implicated include maternal obesity (http://www.autismspeaks.org/blog/2012/04/13/maternal-obesity-autism), complications of prematurity, older mothers, older fathers, having children too close together, etc.
Perhaps the most important recent news on the cause of autism is what doesn’t cause autism: immunizations. The now infamous Andrew Wakefield published so-called evidence in Lancet (Wakefield et al, 1998) that linked the MMR (measles, mumps, rubella) immunization to autism causing an epidemic of fear over vaccinations resulting in marked reductions in immunization rates (with resulting return of these lethal childhood diseases). Turns out that Wakefield had been secretly payrolled to create evidence against the shot and, while planning extraordinary business schemes meant to profit from the scare, he had concealed, misreported and changed information about the children to rig the results published in the scientific journal! Wakefield has since been disbarred from the profession, the Lancet retracted the article (for the first time in its history!) and the Institute of Medicine (IOM) one of the most respected scientific bodies in the U.S. has declared that upon review of all the evidence, immunizations do not cause autism.
Taken together all these articles suggest that the cause of autism is in the interaction between genes and environment. The environment is pre-natal i.e. in the womb exposure when the fetus’ brain is developing or peri-natal (during or right after birth) when the brain is most vulnerable and not post-natal (i.e. not due to immunizations, diet, vitamins, allergens, etc.). In other words the child must be predisposed genetically and when exposed environmentally then he or she would be more likely to develop autism. The next step for researchers will be to identify the specific toxins that are contributing to the causes of ASD.