Thursday is Autism Awareness Day. About 1 in 150 kids in North America is affected by autism. The number has risen dramatically in the past decade, partly because children are being diagnosed at a younger age.

Doctors have better diagnostic tools to recognize the developmental condition. Still, each child who has autism acts differently, making the diagnosis sometimes difficult. But there are some telltale signs that can point to an accurate diagnosis as early as 18 months of age.

"If they're not speaking, if they're not pointing, if they're not using gestures, if they're not interested in other children or interested in their parents," says Catherine Trapani of the Marcus Autism Center.

If you notice any of those signs you should make an appointment with your doctor, the sooner the better, because early intervention can help prevent social and language problems.

Right now a baby's behaviour may provide clues. The first signs may be seen as young as six months. Here are some subtle signs to watch for

The baby does not turn when you call your baby's name, or does not turn to look when you point to an object, if there is a lack of babbling especially by one year of age. Also late smiling; most babies smile by two month of age, and if there is a failure to make eye contact with people

Most kids form attachments to soft objects like a stuffed animal or blanket -- it's suggested that children with autism spectrum disorders prefer hard items, like flashlights or keys.

For more information on the practical aspects and the latest research a good website for parents is Autism Speaks.