Causes of autism are largely unknown. However, there are a number of theories surrounding the cases of autism that we see. There are also some conflicting opinions focusing on whether or not there has been a sharp rise in the cases of autism in the past 10 years.
If you have an autistic child, it is important to know that autism is not a psychological disorder. Researchers have long dispelled the myth that autism is caused by the lack of a nurturing mother. Hence, if your child has been diagnosed with an autism disorder, know that it is not caused because you were a bad parent.
Genetic Causes Of Autism
Many studies strongly suggest that autism cases are caused by inherited genes. It has been found that the incidence of autism in the general population is approximately 1.5 in 1000 people, but parents with an autistic child have a 1 in 20 chance of having another autistic child.
Many neurobiologists also say that autism is the most heritable of all the neurobiological conditions. The most persuasive evidence is the research done in twins. Twin studies can help establish a genetic link for a condition by noting the difference in prevalence of the condition in identical (monozygotic) and fraternal (dizygotic) twins. If a condition is genetic in origin, the prevalence will be markedly higher in monozygotic twins, since they share the exact same chromosomes. In most twin studies conducted for autism, the prevalence of autism is as much as 90% higher in monozygotic twins than in dizygotic twins.
The studies themselves are subject to controversy, however. The fact that not one of the studies showed 100% concordance in monozygotic twins suggests that there could be other factors at play in the cause of autism. Other familial studies have noted common characteristics for instance, that autism is more common in families of physicists and engineers.
This observation gave rise to the term the geek syndrome to identify autism.
Environmental Causes Of Autism
There are also many researchers who believe that environment factors can be causes of autism. Dr. Bernard Rimland proposed in 1967 that autism is caused by mercury and heavy metal toxicity to which some children have a genetic sensitivity. His treatment of autistic children with a gluten-free, casein-free diet and mercury chelation therapy (removal of mercury from the system) has shown great success with some children.
Other environmental factors that can possibly play a part in causing autism include viral or bacterial infections, vaccines and thalidomide.
The Supermale Brain Theory
One particularly interesting recent theory is that autism is caused by high levels of testosterone during development. A study in England measured the testosterone level of the amniotic fluid in mothers, then followed up with testing of children after birth and at four years. They found that the babies with the highest levels of testosterone pre-birth had a smaller vocabulary and made eye contact less often at a year old, and were less socially developed at age four.
The theory concludes that high testosterone levels in the brain support the development of male skills like analysis of systems and seeing patterns, but repress the development of female skills like communication and empathy. Autistic children tend to be lacking in the female skills.
