Symptoms of autism spectrum disorder (ASD) usually appear between the ages of 2 and 3, although children are often not diagnosed until age four. While signs of autism can be seen in babies, problematic behavior (withdrawn, aggressive or repetitive behaviors) and language difficulties frequently emerge after normal infant and toddler development. Social interaction is severely limited.
See our article Symptoms of Autism Spectrum Disorder for details on signs and symptoms of ASD.
Two million people have the diagnosis in the USA, reflecting a dramatic increase in the disorder over the past 40 years. Reasons for the symptom increase in recent decades are assumed to include environmental factors in addition to greater awareness and changes in diagnostic criteria.
Current research includes efforts to discover early causes and signs of autism so treatment interventions can begin as soon as possible.
A diagnosis is made based on behaviors; no blood test can determine the presence of autism spectrum disorders. Parents who notice unusual behaviors or changes in their child’s developmental progress should discuss the situation with a trained professional as soon as possible.
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