The large number of autistic individuals with unaffected family members may result from spontaneous structural variation — such as deletions, duplications or inversions in genetic material during meiosis.
Children with high-functioning autism suffer from more intense and frequent loneliness compared to non-autistic peers, despite the common belief that children with autism prefer to be alone.
Making and maintaining friendships often proves to be difficult for those with autism.
Selectivity is the most common problem, although eating rituals and food refusal also occur; this does not appear to result in malnutrition.
Although some children with autism also have gastrointestinal symptoms, there is a lack of published rigorous data to support the theory that children with autism have more or different gastrointestinal symptoms than usual; Siblings of children with ASD report greater admiration of and less conflict with the affected sibling than siblings of unaffected children and were similar to siblings of children with Down syndrome in these aspects of the sibling relationship.
Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name.