Autism Signs and Symptoms

Signs of autism may appear during infancy and the disorder is usually diagnosed by the age of 3. Sometimes the child's development appears normal until about 2 years old and then regresses rapidly. Symptoms of autism occur in various combinations, from mild to severe.

Infants with the disorder often display abnormal reactions to sensory stimuli (i.e., senses may be over- or underactive). Touches may be experienced as painful, smells may be overwhelmingly unpleasant, and ordinary daily noises may be painful. Loud noises (e.g., motorcycle going by, vacuum cleaner) and bright lights may cause inconsolable crying.

Other signs of the disorder in infants include the following:

  • Appears indifferent to surroundings
  • Appears content to be alone, happier to play alone
  • Displays lack of interest in toys
  • Displays lack of response to others
  • Does not point out objects of interest to others (called protodeclarative pointing)
  • Marked reduction or increase in activity level
  • Resists cuddling

In November 2013, results of a study funded by the National Institutes of Health (NIH) and published in Nature indicated that attention to others' eyes declined in 2- to 6-month-old infants who were later diagnosed with autism. Further research is needed, but it may be that identifying this marker for autism in such young babies and taking appropriate measures earlier may help keep the children's social development on track.

Young children with autism usually have impaired language development. They often have difficulty expressing needs (i.e., use gestures instead of words) and may laugh, cry, or show distress for unknown reasons. Some autistic patients develop rudimentary language skills that do not serve as an effective form of communication. They may develop abnormal patterns of speech that lack intonation and expression and may repeat words or phrases repetitively (called echolalia). Some children with autism learn to read.

Autistic children do not express interest in other people and often prefer to be alone. They may resist changes in their routine, repeat actions (e.g., turn in circles, flap their arms) over and over, and engage in self-injurious behavior (e.g., bite or scratch themselves, bang their head).

Other symptoms in young children include the following:

  • Avoids cuddling or touching
  • Frequent behavioral outbursts, tantrums
  • Inappropriate attachments to objects
  • Maintains little or no eye contact
  • Over- or undersensitivity to pain, no fear of danger
  • Sustained abnormal play
  • Uneven motor skills
  • Unresponsiveness to normal teaching methods and verbal clues (may appear to be deaf despite normal hearing)

Symptoms of autism may increase in severity when the child enters adolescence and often decrease in severity during adulthood.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 28 Feb 2000

Last Modified: 01 Sep 2015