How early can autism be diagnosed?

When Pam Lyle's daughter Hailey was 13 months old, she suddenly lost her ability to speak and began retreating into her own world. Two months later, Lyle brought her to Yale University's Child Studies Center, where she got a diagnosis that is unusual for a child that young: autism.

Now, after 2 1/2 years of intensive in-home treatment, Hailey makes eye contact and recently has learned to use pictures to communicate — an outcome the Orange, Conn., family attributes to her early diagnosis.

Many specialists say autism isn't identifiable in most children until at least 18 months of age, when the behaviors that are the common hallmarks of the disorder are more apparent. While there are no statistics on average age of diagnosis, many children aren't diagnosed until age 3 or later. But thanks to studies showing that preschoolers often respond better to treatment than do children diagnosed at earlier ages — as measured by gains in language and IQ scores — specialists are exploring whether children diagnosed at even younger ages might fare even better.

Several studies, including research in Canada and at the University of California, San Diego, have tied the eventual diagnosis of autism to attributes observed in infants as young as 6 months of age. Autism specialists around the country say parents are increasingly bringing in toddlers and infants — some as young as 4 months — for evaluation.

At the Center for Autism and Related Disorders at the Kennedy Krieger Institute in Baltimore, director Rebecca Landa says it once was rare to see even a toddler, but now the clinic sees "a minimum of one baby a week." Yale University's center is seeing a child under the age of 18 months every few weeks, says director Fred Volkmar. And researchers are eager to see these youngest patients. Whereas many families must wait a couple of years for an appointment at Yale, children under age 2 can get in to see a specialist in a few weeks to a couple of months.

Autism, a little-understood condition marked by social withdrawal, repetitive behaviors and poor communication skills, is believed to be the fastest-growing developmental disability. There are varying theories as to why autism is on the rise, from the use of mercury preservatives in childhood vaccines, to increased awareness driving more diagnoses. The Centers for Disease Control and Prevention in Atlanta estimates about 24,000 children are diagnosed annually, and that as many as 500,000 children in the United States have the condition.