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Autism Symptoms

Written by Olivia Cerf, FoundHealth.

Autism may be noticed during infancy. But, it is usually noticed during early childhood (ages 2-6 years). Sometimes there is an event seemingly associated with the onset of symptoms, such as vaccination, infection, or seizure. The severity of symptoms varies. Children with autism may exhibit a combination of behaviors. Autism is a lifelong condition.

Each child is different, but symptoms fall into four broad categories:

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

Because children develop and change so rapidly at this early stage, symptoms often take the form of failure to progress or of regression from previous achievements. Something wrong may be apparent at birth, but it is more common for suspicions to be raised when a toddler fails to achieve normal social and developmental milestones.

The range of unusual behaviors is extensive. Children demonstrate 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, such as using incorrect words and changing the meaning of common words
  • Only echoing what they have heard, not initiating their own speaking
  • Trouble with nonverbal communication—For example, body language is used and interpreted wrongly; a hug may be interpreted as an assault.
  • Not reacting to smiles in the manner expected from a child

Repetitive Behaviors, Unusual Interests, and Activities

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, such as rocking or flapping a hand
  • May make frequent gesturing or fixate on specific objects
  • Demand consistency and predictability in their surroundings—Tiny changes may evoke rage reactions.
  • May be hyperactive, passive, and single-minded
  • Resist change

Altered and Confused Sensory Input

Signs may include:

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

Other Disorders

Some people with autism suffer from other disorders as well, including:

  • Seizures —Seizures occur when the normal pattern of communication between nerve cells in the brain is disturbed. This can cause strange sensations, emotions, and behavior; or, the condition may result in 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:
    • Gastroesophageal reflux disease
    • Malabsorption
    • Diarrhea
    • Not having a lot of food interests
    • Failure-to-thrive
  • Genetic disorders, such as:
    • Tourette syndrome —This is a neurological disorder that is characterized by tics, rapid, involuntary movements, or sounds that occur repeatedly.
    • Fragile X syndrome —This is a hereditary disorder of the X chromosome, the most common cause of inherited mental retardation.
    • Phenylketonuria (PKU) —PKU is a genetic disorder of the enzyme that breaks down phenylalanine, which is an amino acid found in certain foods. Without a proper diet, PKU can lead to mental retardation.
    • Tuberous sclerosis—This is a genetic disorder of the nervous system that causes tumors to grow on the nerves in any part of the body. Neurofibromatosis can also produce other abnormalities, such as changes in the skin and deformed bones.



Autism Society of America. Autism 101 course. Autism Society of America website. Available at: . Accessed June 15, 2010.

Autism spectrum disorders (pervasive developmental disorders). National Institute of Mental Health (NIMH) website. Available at: . Accessed September 10, 2010.

Behrman RE, et al. Nelson Textbook of Pediatrics. 18th ed. Philadelphia: Saunders, 2007.

DynaMed Editorial Team. Autistic disorder. EBSCO DynaMed website. Available at: . Updated September 13, 2010. Accessed September 14, 2010.

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.

Rapin I. An 8-year-old boy with autism. JAMA.2001;285:1749-1757.

Stern TA, et al. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia: Mosby Elsevier, 2008.

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