From PEOPLE Magazine Click to enlarge
Watching her infant son undergo a series of developmental tests last year, Teri Chason at first saw no cause for alarm. Bennett, then 6 months old, was a happy baby who cooed on cue, and he quickly figured out if he pulled on a lever, it triggered a musical bear. But when his head lolled backward as Dr. Rebecca Landa gently pulled him into a sitting position, Chason says she began to "freak out a little." Was that a sign Bennett would have autism like his older sister Addison? With a slight edge in her voice, Chason told the doctor, "I haven't seen him do that before." But each time Landa repeated the test, Bennett's head dragged. "When I saw that," said Landa, director of Kennedy Krieger Institute's Center for Autism and Related Disorders in Baltimore, "my heart sank."

It's too soon to tell whether Bennett will have autism: Most of the classic signs like repetitive behavior often aren't apparent until after a child turns 1 or even 2. But for many researchers and pediatricians-and worried parents who already have one child with the incurable disorder-there's a growing urgency to test higher-risk younger siblings as early as possible (see box). The hope is to identify the earliest, most subtle signs of autism so specialists can begin treating them. "The brain is most malleable in the first years of life," explains Dr. Ami Klin, who heads Yale University's autism program. "If you want to treat the disorder, you don't have to wait until it's a reality." Still, even supporters of the research say you have to be careful. "There is a real risk for overdiagnosis: Some of the early signs of autism are also signs of other developmental delays," says Dr. Susan Hyman of the University of Rochester Medical Center.

Chason, though, is a firm believer. Her daughter Addison, 7, is one of the nearly 1,000 children Landa has treated in early-intervention programs she developed. Diagnosed at 2, Addison could only say a few words when she began therapy-far fewer than her peers-and relied mostly on sign language. Speech and behavioral specialists worked with her for six months, both one-on-one and in a bright, preschool-like setting, using songs and games to encourage speaking. Today Addison is a chatty first grader who only requires occasional assistance from an aide in her classroom. "She still sometimes words questions awkwardly," says Chason, "but she's a very successful first grader." Landa says Addison is a rare case who is "indistinguishable from her peers," but even so, many children who undergo early intervention "will go on to have typical IQs and be in regular classrooms."

So when Landa expressed concern about Bennett-whose low muscle tone and weak fine motor skills could be early warning signs-Chason, 34, a homemaker, and her husband, Todd, 33, an environmental lawyer, acted fast. Chason (whose middle daughter, Cassidy, 3, doesn't have autism) took Bennett to a local Infants and Toddlers program, where he began receiving physical therapy for the low muscle tone in his neck, body and legs. Just last week Bennett, now 14 months old, took his first steps. Still, the Chasons are being cautious; Bennett will visit Dr. Landa in April for more tests. "We've seen how early intervention pays off, so why would we wait?" Chason says. "Anything we do now is going to be beneficial."