Autism cases are on the rise. Or so the most recent data would have us believe. The Centers for Disease Control and Prevention (CDC) found that 1 in 100 children in the U.S. have been diagnosed with autism spectrum disorder (ASD) — up from 1 in 150 in 2007. A study in the journal Pediatrics in October 2009 revealed similar numbers — parents of 1 in 90 children reported that their child had ASD. With boys, the rate of ASD was 1 in 58. Without a doubt, autism is the country’s fastest-growing developmental disability, affecting more children than cancer, diabetes and AIDS combined. Still, in dealing with a childhood disorder that ranges from “highly functioning” to uncommunicative, and such a long list of potential triggers and treatments, even the numbers themselves are subject to questioning.

“It irritates me to no end that we still argue over whether there is an increase in incidence,” says Michael Merzenich, Ph.D., a neuroscientist at the University of California San Francisco who has pioneered research in brain plasticity (essentially, retraining brains) and leads the brain-training software company Posit Science. “I think there is lots of evidence for increased incidence,” Merzenich says. “Overwhelmingly it supports that there are things in the environment that are contributing to the rate of incidence. But people still argue.”

Doubters point out that autism is better understood today and more frequently diagnosed. Some have even suggested that an autism diagnosis may be a means to an end — a way for parents to get the immediate speech and physical therapies their children need to prevent long-term delays. Massachusetts-based health writer Lisa Jo Rudy, mother to one autistic child, Tom, 13, as well as to a 10-year-old daughter, Sara, is one such skeptic. “Are we simply calling what used to be called being a ‘dweeb’ autism?” Rudy asks. The National Institute of Mental Health writes: “It is unclear from the report in Pediatrics whether the 1 in 90 estimate is measuring a true increase in ASD cases or improvements in our ability to detect it.”

Researchers like Merzenich say the waffling over numbers is beside the point — too many children are living with the disorder, and not enough research is focusing on what’s causing it or how best to treat it. The term “autistic” was not even part of the modern lexicon until it was introduced by Hans Asperger and Leo Kanner in the 1940s — the word itself (containing the Greek autos) describes the self-absorption that is a hallmark of the disorder. While it takes many forms, autism affects social interaction and communication and leads to the development of intense habitual interests. Often, after a year of seemingly normal interaction, autistic kids will fail to respond to stimuli, make eye contact or turn at the sound of their name. They may not talk readily, or they may repeat themselves incessantly. They are likely to follow compulsive behavior, such as shaking their hands, stacking objects or repeating daily activities the exact same way each day. The treatment is years of intensive — and expensive — therapy.