That may be why autistic kids cling to these repetitive activities and rituals — these provide them with a sense of predictability and structure, which is comforting, Dr. Powers explains.

Although researchers aren't sure just what causes the brain's wiring to go awry, studies suggest that autism's roots lie in a person's genes. In a recent study, Karin Nelson, MD, a child neurologist with the National Institutes of Health, and her colleagues compared blood drawn from newborns later diagnosed with autism with the blood of typical infants. The blood of the autistic babies contained vasoactive intestinal peptide, a protein molecule that affects brain development. Researchers are also looking into other possible genetic markers for autism, in hopes that high-risk babies might be identified and treated sooner with current therapies. Dr. Nelson hopes that such knowledge will also lead to the development of new therapies.

Congress recently mandated increased federal funding to examine autism, including the establishment of five research centers. So experts hope to have a clearer picture before long.

Why Is Autism on the Rise?
Researchers aren't just looking into exactly what causes autism — they're also probing reasons for its recent skyrocketing incidence. Autism is so perplexing and mysterious that experts are beginning to worry that something in the environment may be causing it — but so far, there's no evidence to support that, says Dr. Sandler.

In fact, many experts say that the rise may not be due to more kids being afflicted with autism, but rather more cases being diagnosed. Today, experts talk not just about autism, but about autism spectrum disorder, which encompasses a greater range of symptoms. It's possible that many of today's kids with autism used to be called something else, such as learning disabled or mentally retarded, says Dr. Powers. Other kids might have been labeled eccentric or unusual — but not disabled.