Autism is a brain disorder characterized by social problems, language trouble, and strange, repetitive behaviors — although there's a wide variation among cases. Many children with autism exhibit baffling behaviors, such as constantly flapping their hands or walking on their toes. They might insist on highly organized or rigid activities, maybe eating only beige foods or constantly carrying around some object, such as a piece of string, says Michael Powers, PsyD, director of the Center for Children with Special Needs in Tolland, Connecticut, and assistant clinical professor of psychology at the Yale University Child Study Center.

And the disorder appears to be more and more common. According to Adrian Sandler, MD, chair of the American Academy of Pediatrics' committee on children with disabilities, it used to be five children in 10,000 who had autism — now it's four or five in 1,000. Many experts attribute the surge in diagnoses at least in part to greater awareness of this mysterious disorder, which leaves children emotionally bereft. Kids with autism are not only unable to communicate their own thoughts and feelings, but they're also unable to understand the emotions of other people. These children have difficulty putting themselves in someone else's place, says Dr. Powers, and so they won't engage in play and pretending, or respond to others by smiling or nodding.

What Causes Autism?
Researchers are working harder than ever to pin down the source of this confusing condition, which was first described in 1943. Initially, experts pegged autism as a psychological condition and blamed poor parenting. But the current thinking is that autism is a disorder of the brain.

By studying the brains of older autistic patients, researchers have discovered an absence of certain nerve cells in different parts of the brain, including the prefrontal cortex, which assigns emotional states to others — enabling one to understand, say, the difference between a dog that's wagging its tail and one that's snarling. Another impaired area is the amygdala, which allows for emotional learning, such as recalling the meaning behind a facial expression.

Ultimately, autism deprives children of a brain that can easily pull pieces of information together into a unified whole. Instead of seeing the big picture, they see the world as little parts, says Dr. Powers.