Believe it or not, autism can begin to show symptoms in babies as young as 6 months of age. Here are a few signs to look for: No signs of happiness, smiles, joyfulness by 6 months. No mirrored smiles, facial expressions or sounds by 9 months. Not responding to name by 12 months. No baby talk or baby babbling by 12 months. No waving, pointing, reaching and like gestures by 12 months. Not speaking words by 16 months.