Autism Causes

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Genetic Causes

Autism is a complex genetic disorder. It is one of the most heritable of psychiatric illnesses, with identical twins having up to a 90% chance of sharing the diagnosis. About a hundred autism-linked genes have been discovered so far, most of them overlapping with other disorders such as epilepsy and ADHD. But despite mounting evidence for its genetic origins, autism cannot be explained by a single gene—nor a dozen. It is not known precisely how many genes are involved, nor precisely how genetic factors interact with environmental ones to predispose a child to autism. Some have suggested that the autism spectrum is not a single disease with a single genetic cause, but a collection of rare disorders caused by several different genetic variations.

Environmental and Epigenetic Causes

In the past many scientists were skeptical of non-genetic explanations for autism. It is becoming clear that disorders on the autism spectrum result from an interaction between genes and other factors such as prenatal and environmental conditions. No toxin has been shown to single-handedly cause autism, but environmental conditions may affect children with some genes more than others. The conditions guiding the expression of genes within a cell, known as epigenetics, may also help to explain why autism emerges. Some researchers have suggested that the genes of an autistic child may not be altered at all, but simply expressed differently.

Other Causes

Despite the uncertainly about the causes of autism, two often-cited causes can be ruled out immediately. First, mercury in childhood vaccinations do not cause autism. Population studies have found no evidence for a connection between vaccination and autism. Mercury was removed from vaccines more than a decade ago in California and rates of autism have continued to rise there. Second, autism is not the result of bad parenting. When the disorder was first identified in the US in the 1950s, some conjectured that children with autism were guarding themselves against the rejection of a ‘refrigerator mother.’ This view proved mistaken. Autism has many causes, but absence of sufficient love is not one of them.