VANCOUVER—Geneticist Wendy Chung took to the TED stage on Wednesday to discuss one of today’s most perplexing problems: the twenty-fold increase in autism diagnoses in children over the past three decades. What we know for certain (and what she made clear) is that vaccines are absolutely not to blame. There is no credible evidence to support the assertion that vaccination causes autism, and there is plenty of evidence to rule it out.

Autism diagnoses are certainly on the rise, though; one in 88 children will be diagnosed with autism this year. But the rise of diagnoses does not necessarily mean that there has been a rise in autism. In fact, Chung does not believe that there has been a massive increase in autism cases. “The vast majority of it is the increase in diagnoses,” Chung said. Medical professionals are now far better trained to detect and diagnose autism, so it's diagnosed more often.

At the same time, autism is not a single disorder. It's actually a spectrum of disorders, from the completely debilitating to milder cases that may only affect socialization or education.

There’s also an important practical matter to consider: the passage of the Individuals with Disabilities Educational Act in 1990. This act authorized support for special needs children, including those along the spectrum of autism. Suddenly, parents, teachers, and doctors had practical reasons to identify autism: to get educational help.

But what causes autism? “There’s probably not one single answer,” Chung said. One correlation we've discovered is with children born to older parents. We also now see connections with exposure to certain chemicals during pregnancy. But Chung’s work is focused on the genetic component, which is becoming more and more important not only to diagnosis but to treatment.

Skeptical that autism could be genetic? Chung noted that males are affected at a four-to-one ratio compared to females. This seems to suggest that there is indeed a genetic component. But even in the case of identical twins, autism only occurs in both twins 77 percent of the time. Through a huge number of studies, scientists have found that with some individuals, the cause is a single gene. With others, it can be a combination of genetic influences. Indeed, there could be 200-400 genes that may promote autistic symptoms, which helps to explain why we see such a broad spectrum of its effects.

A common objection some parents have to the genetic argument is that they don't believe autism runs in their family. However, certain individuals can have autism that is genetic but not inherited. Genes can and do mutate in between generations. Through an examination of the DNA changes that occurred in families with affected children, at least 25 percent of the genetic cases were traced to these "de novo" mutations.

Can we use this knowledge to intervene? In the case of genetic issues, early identification could potentially help us target the involved genes with drugs. A better genetic understanding of the autism spectrum could also feed into education interventions. With a clearer picture of the actual changes that underly the outward behavior, we might be able to develop more customized educational programs for children affected by autism.