Symptoms of Autism

Autism can be noticed during infancy. It is usually noticed during early childhood, which is between the ages of 2-6 years. The severity of symptoms varies. Children with autism may show a combination of behaviors. Autism is a lifelong condition.

Each child is different. Symptoms fall into 4 broad categories:

  • Poor or limited social relationships
  • Underdeveloped communication skills
  • Repetitive behaviors and unusual interests and activities
  • Signs of altered and confused sensory input

Children develop and change rapidly at this early stage. Symptoms often take the form of failure to progress. A child may also regress from previous achievements. Something wrong may be noticed at birth. However, it is more common to notice something wrong when your child is a toddler. They may not achieve normal social and developmental milestones.

The range of unusual behaviors is wide. Children have many different combinations of behaviors.

Poor or Limited Social Relationships

Symptoms may include:

  • Avoiding eye contact
  • Avoiding social contact and preferring to be alone
  • Not imitating others
  • Not understanding other people's feelings and needs
  • Failing to seek and even avoid personal attention
  • Being physically aggressive
  • Being self-destructive
  • Often having tantrums, even with very little to provoke them

Underdeveloped Communication Skills

Symptoms may include:

  • Never speaking—Some children with autism may not be able to learn how to speak. Or, they may only speak a few words.
  • Using language in unusual ways. Some children use incorrect words and change the meaning of common words.
  • Only echoing what they have heard, and speaking on their own.
  • Trouble with nonverbal communication—Body language is used and interpreted wrongly. For example, a hug may be considered an assault.
  • Not reacting to smiles the way a normal child would.

Repetitive Behaviors, Unusual Interests, and Activities    TOP

Autistic children usually:

  • Do not play imaginatively
  • Lack interest in normal activities for their age
  • May spend hours doing a single activity over and over again. For example, rocking or flapping a hand
  • May gesture frequently, or stare at specific objects
  • Demand consistency and predictability in their surroundings—Tiny changes may cause angry reactions
  • May be hyperactive, passive, and single-minded
  • Resist change

Altered and Confused Sensory Input    TOP

Signs may include:

  • An unusual sensitivity to sound, smell, taste, sights, and touch
  • Responding to stimulation in unusual ways
  • Sniffing or licking toys
  • Feeling pain from a light touch, but ignoring more severe pain
  • Experiencing sounds as colors, and touches as sounds

Other Disorders    TOP

Some people with autism have other disorders as well. These may include:

  • Seizures —These occur when communication between nerve cells in the brain is disturbed. This can cause strange sensations, emotions, and behavior. Also common are convulsions, muscle spasms, and loss of consciousness.
  • Intellectual disability —A condition that includes limitations in both intelligence and adaptive skills.
  • Conditions affecting digestion, such as:
  • Failure-to-thrive
  • Genetic disorders—Examples include:
    • Tourette syndrome —This is a neurological disorder. The symptoms are tics, rapid, involuntary movements, or sounds that occur repeatedly.
    • Fragile X syndrome —This is an inherited disorder of the X chromosome. It is the most common cause of inherited intellectual disability.
    • Phenylketonuria (PKU)—PKU is a genetic disorder of the enzyme that breaks down phenylalanine. Phenylalanine is an amino acid found in certain foods. Without a proper diet, PKU can lead to intellectual disability.
    • Tuberous sclerosis—This is a genetic disorder of the nervous system. It causes tumors to grow on the nerves in any part of the body. Neurofibromatosis can also produce other abnormalities. For example, changes in the skin or deformed bones.


About autism. The Autism Society website. Available at:
...(Click grey area to select URL)
Accessed March 14, 2017.
Autism spectrum disorder. National Institute of Mental Health website. Available at: Updated October 2016. Accessed March 14, 2017.
Autism spectrum disorders. EBSCO DynaMed Plus website. Available at: http://www.dynamed.... Updated April 29, 2016. Accessed March 14, 2017.
Behrman RE, et al. Nelson Textbook of Pediatrics. 18th ed. Philadelphia: Saunders, 2007.
Goetz CG. Goetz’s Textbook of Clinical Neurology. 3rd ed. Philadelphia: Saunders, 2007.
Jacobson JL, Jacobson AM. Psychiatric Secrets. 2nd ed. Philadelphia: Hanley & Belfus, 2001.
Stern TA, et al. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia: Mosby Elsevier, 2008.
Last reviewed March 2017 by Adrian Preda, MD
Last Updated: 3/15/2015


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