Common Symptoms of Autism

An Overview of Autism Symptoms

It's said that "if you've met one person with autism, you've met one person with autism." That's absolutely right. That's because the appearance of autism can vary from person to person. One person with autism may be very verbal, bright, and engaged, while another is non-verbal, intellectually challenged, and almost entirely self-absorbed.

With such a wide range of possible symptoms, how is it possible to identify autism?

Common Signs and Symptoms of Autism

The National Institutes of Mental Health has created a list of symptoms that are often seen in autism. It's important to bear in mind that none of these symptoms on their own is likely to indicate autism. Autism is a pervasive developmental disorder, which means that a child must have many of these symptoms in order to qualify for a diagnosis.

By the same token, however, many children reach early milestones on time (or even early) and still qualify for an autism spectrum diagnosis.

 While some children may seem to develop typically for a while and then develop symptoms, others may have obvious symptoms from infancy.

Early signs and symptoms of autism include:

Symptoms of autism must be present before the age of three to qualify for a diagnosis. Some children, however, have mild symptoms that may not be obvious at a very young age.

Such children may, as a result, be diagnosed after the age of three. When that happens, it's usually because they have several of the symptoms listed below.  

Later indicators include:

If symptoms such as these suddenly appear in a child older than three, and those symptoms were definitely not present from an earlier age, the child would not qualify for an autism diagnosis. He would, however, almost certainly receive a different developmental or psychiatric diagnosis.

Less Common Signs & Symptoms of Autism

In addition, people with autism seem to be more prone to other problems not listed in the diagnostic criteria. These problems include sleep disorders, gastrointestinal disorders, self-abusive behavior, and more.

In addition to these associated issues, people with autism are more likely to experience:

  • seizures
  • intellectual disability
  • savant syndrome (extraordinary abilities in one very specific area)
  • hyperlexia (early ability to decode words without understanding them)
  • synesthesia (association of words or ideas with sounds, colors, tastes, etc.)
  • low muscle tone and/or difficulties with fine and gross motor skills

Signs & Symptoms of Autism in Boys and Girls

The vast majority of people diagnosed with autism are boys and men. This may be, in part, because autism tends to look very different in girls and women and, as a result, it may not be recognized as often.

In general, boys with autism show overt symptoms such as "stimming" (pacing, flicking fingers, rocking). They may be quite loud, get upset easily, or become angry when required to take part in activities that are outside their comfort zone. These behaviors, naturally, draw the attention of parents, teachers, and doctors.

Girls and women with autism, on the other hand, tend to be very quiet and withdrawn.

They are often loners who choose not to participate in group activities. Because our culture accepts the notion that girls are often quiet and unengaged, these behaviors are much easier to mistake for shyness or normal social reticence.

Our Autism Symptoms Checklist may be useful to you as you consider the above in relation to your own child. It's also important to remember that there are different types of autism, which will need to be considered by a doctor when/if making a formal diagnosis.

Diseases and Conditions That Are Similar to Autism

Most of the symptoms of autism are also symptoms of other developmental and mental health disorders. As a result, it is not unusual for children with autism to have multiple diagnoses. It is also relatively common for children to start out with one diagnosis and finally wind up with an autism spectrum diagnosis.

A few similar and/or related disorders include:

    When to See Your Doctor

    It can be very tough for a parent to determine whether behaviors are symptoms of autism or just ordinary variations in development. How much "lining up of toys" is excessive? How much desire for repetition is normal?

    There is also the possibility that some developmental differences are caused by non-autism-related issues. For example, not responding to a name could very well be a symptom of a hearing impairment. Late talking could be due to aphasia or apraxia of speech

    To properly diagnose autism, professionals use a set of specific tests that actually measure a child's symptoms. They may also decide that your child should undergo testing for hearing impairment or speech issues that are unrelated to autism.

    For that reason, if you're concerned about your child, we encourage you to take your concerns to your pediatrician. If their pediatrician is not able to help, and you still have worries, it may be time to make an appointment with a developmental pediatrician or other diagnostician.

    A Word From Verywell

    While people with autism have many challenges, they often have extraordinary strengths and positive traits. If you are concerned that someone you care about may have autism, we encourage you to remember that a diagnosis is just a way to describe a set of traits and challenges. It doesn't change anything except access to treatments and services that might otherwise be out of reach.


    American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington, VA: American Psychiatric Association; 2013.

    Greenspan, Stanley and Weider, Serena. "Engaging Autism." Da Capo Press:2006.

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