Autism Autism is one of the mental, emotional, and behavior disorders that appears in early childhood. Autism, or autistic disorder, almost always develops within the first 3 years of a child's life. Children and adolescents with autism cannot interact normally with other people. Autism thus affects many aspects of their development. Children with and adolescents with autism typically: -have a difficult time communicating with others -exhibit very repetitious behaviors (like rocking back and forth, head banging, or touching or twirling objects); -have a limited range of interests and activities; and -may became upset at a small change in t