What Do We Know About Autism?

As a child, I learned how autism turns a world upside down. In our house, it was my little brother who was diagnosed at 3. In the search for a treatment, parents will go to any lengths. I saw that with my parents, and I see it now as a practicing physician. Much has changed in the field of autism, but the need for parents to make decisions in a bewildering terrain has hardly changed at all.

A diagnosis of autism usually rests on three distinctive symptoms: difficulty with social interaction, problems with verbal and nonverbal communication, and repetitive actions or obsessive interests. These behaviors can range from mild to disabling.

Parents may first notice that something is wrong when their child fails to babble or point by age 1 or to speak by 16 months. Some autistic children don't smile or make eye contact. Others seem to be hearing impaired or do not know how to play with toys. There also are cases in which a child who appears to be making normal developmental progress abruptly loses language or social skills.

Is autism an epidemic?

Until the 1940s, there was no autism—in the sense that it was an unrecognized condition. In 1988, when Dustin Hoffman's "Rain Man" brought a version of autism to life on film, many of us first heard about it—as an odd, almost-fascinating disorder which was also, apparently, rare.

Fast-forward to today. Autism is front-page news. Celebrities talk about it, Congress ponies up millions for research, and the numbers are startling: One in every 150 American kids has some form of autism, says the Centers for Disease Control and Prevention. The last 15 years in particular have seen diagnoses rates soar. "It is the fastest-growing developmental disability in the U.S.," says Dr. Andrew Zimmerman, director of medical research at the Kennedy Krieger Institute Center for Autism and Related Disorders in Baltimore.

No one really knows why the numbers are so high. But there are many theories. The most commonly accepted one centers on how we define and recognize autism. "There has been an expansion in the criteria," explains Dr. Cecelia McCarton, the director of a school for autistic children in New York City, echoing the majority of mainstream experts.

A broader definition means that there are simply more ways to be considered autistic than in the past. At the same time, parents, teachers and doctors are paying more attention to the symptoms—which tends to lead to higher numbers of diagnoses.

But changes in how children are labeled and diagnosed alone "cannot explain the rise," says Dr. Zimmerman. Other theories rest on maternal, obstetric or environmental factors that perhaps trigger an innate tendency. "Anything from autoimmune disorders to chemicals in the environment may be involved," adds Zimmerman. He notes that researchers have been pursuing all of these theories to varying degrees, "but science has not yet pointed us to any concrete answers." An important study released this month suggests that a genetic flaw that occurs around conception may sharply increase the risk that a child will develop autism.

More than perhaps any brain disorder in history, autism has ignited heated arguments among parents and professionals.