It can be hard to tell if a child has autism because many children without the condition have some of the same behavior. Most children with autism spectrum disorder don't get a diagnosis until they're 4 or older.
But the U.S. Centers for Disease Control says that it's possible to get a reliable autism diagnosis as early as age 2. And many parents notice early signs before their child's first birthday and realize something is different by the time their child is 18 months old.
The earlier a child with autism begins treatment, the better the outcome. If you notice any of these signs or have concerns about your child's development, talk with his doctor.