How Autism Is Diagnosed

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There is no easy medical test to diagnose autism. The process includes interviews and observation. A healthcare professional also evaluates speech, hearing, and motor skills. While it's never "too late" to be diagnosed with autism, it's never too early for a screening or evaluation.

Some parents worry that any difference in their child's behavior or development could be a sign of autism. Sometimes these worries are unnecessary. Other times, careful observation can lead to early diagnosis and early treatment. If autism is ruled out, other challenges may be caught and handled sooner.

Treatments and support can make a big and positive difference even if autism is diagnosed in later life.

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Autism Signs

If you think that you or someone you love may have autism, you probably have noticed certain symptoms. Some signs you might notice are lack of eye contact, social problems, speech delays, or odd physical behaviors. These include rocking, finger flicking, or toe-walking.

It can be helpful to look at an autism symptoms checklist.

Older children and adults may have some or all of the symptoms seen in younger children. Most of the time, these symptoms are mild. Late diagnosis means that the person managed to make up for autistic challenges.

If your child has just one or two symptoms, but is otherwise developing normally, your child probably does not have autism spectrum disorder. That doesn't mean that your child has no challenges.

A child who has speech delays but no other symptoms may benefit from speech therapy even if the they do not have autism. Issues like these should be dealt with as soon as possible. A professional evaluation can help start that process.

Recap

There are no tests to diagnose autism. Healthcare professionals use evaluations of certain behaviors and skills instead. Even if someone has a sign or symptom of autism, it does not mean they have it. Other challenges have similar symptoms.

Others' Observations

Other than parents, teachers are often the first to notice signs of autism. Remember that a teacher cannot make a diagnosis even if they are familiar with the signs.

The same is true of friends and relatives who may believe they see signs of autism in your child. It's fine to listen to what they have to say, but they cannot diagnose autism.

Who Can Diagnose Autism?

The "right" health professional to perform an autism evaluation for a child may be a psychologist, a developmental pediatrician, or a pediatric neurologist. Adults will usually see a psychologist or psychiatrist. Your choice will depend on who is available in your local area. Be sure that the expert you choose has experience with and knowledge of autism spectrum disorders.

Tests

Autism cannot currently be diagnosed with a medical test but experts are trying to develop tests now.

In one study, researchers from UC Davis MIND Institute and NeuroPointDX showed a metabolic blood test could detect autism in 17% of kids.

Currently, testing is limited to interviews, observation, and evaluations. Screening may include:

  • IQ tests to check for intellectual challenges
  • Speech evaluations to check your child's ability to understand and use spoken speech
  • Occupational therapy tests to check for age-appropriate fine motor skills. They also check for visual and spatial awareness, sensory responses, and other neurophysical concerns
  • Hearing tests to ensure symptoms are not caused by hearing loss
  • Autism-specific questionnaires, such as the ADI-R. These allow parents to discuss their child's milestones, behaviors, sensitivities, challenges, and strengths
  • Other tests, such as the Autism Diagnostic Observation Scale (ADOS) and the Checklist for Autism in Toddlers (CHAT). These review children's behaviors based on norms

None of these tests are perfect and some can be misleading. IQ and speech tests are written for typically-developing children. Children being tested for autism almost always have behavioral and speech challenges. These challenges can get in the way of the testing process, making outcomes difficult to interpret.

Even when a professional provides an opinion, the opinion may not be final. It's not unusual to hear, "It could be autism, but he's still very young. Why don't you check in again in six months and we'll see how he's doing?" This can be very upsetting, but it's sometimes unavoidable.

Imaging

There are no imaging tests to diagnose autism spectrum disorder. However, there is research on detecting autism early with brain scans.

These studies include structural magnetic resonance imaging (MRI) scans and functional connectivity MRI scans. These studies have mostly been done on babies who have a sibling with autism. Those babies have a higher chance of having autism.

MRI does not use radiation. This means that it is of lower risk than other types of imaging that do. It is noisy and requires the child to be very still, so it can be hard to get a useable scan.

Differential Diagnoses

In many cases, children have challenges that look like autism but turn out to be simple delays or other issues. For example, not responding to a name could be hearing impairment. Late talking could be due to aphasia or apraxia of speech. These occur because of brain damage.

A child could also have a learning disability, attention deficit hyperactivity disorder, or obsessive-compulsive disorder. Other possible conditions are narcissistic personality disorder, oppositional defiant disorder, or hyperlexia. The child may have both autism and one of these conditions, or autism alone.

Common co-occurring mental illnesses for people with autism include depression and anxiety. People with autism have these conditions more often than other people.

Summary

There are no perfect medical tests to diagnose autism. Healthcare professionals use interviews and observations to help diagnose this condition. The first signs of autism might be noticed by parents, teachers, or family friends.

Even when a health professional thinks someone might have autism, they may not make a final decision right away. They will want to be sure of the diagnosis because some other conditions have similar signs.

A Word From Verywell

For many families, an autism diagnosis can be overwhelming. It may seem to change everything. But your child or adult loved one is still the person they always were, and there's plenty of help, hope, and support available. Time, patience, and learning more about autism can go a long way in the journey ahead.

Frequently Asked Questions

  • At what age should a child be tested for autism?

    Children can be tested for autism as early as 18 months (or even younger in some cases), and reliably diagnosed by age 2. That said, many children don't get a full diagnosis until they're school-age or beyond.

  • Can autism go undetected?

    Yes. Autism is most often diagnosed in children, but can go undetected for years in adults, largely due to the fact that in some cases, the individual has been able to compensate for certain challenges. However, this also means that many people living with undiagnosed autism likely haven't received access to the support and services from which they might benefit.

  • How is autism diagnosed in children?

    In children, autism is diagnosed with an autism evaluation conducted by a psychologist, developmental pediatrician, or pediatric neurologist. Because there's no single imaging scan or blood test that can diagnose the condition, evaluations include several different diagnostic tools:

    • IQ tests
    • Speech evaluations
    • Occupational therapy evaluations
    • Hearing tests
    • Autism-specific questionnaires
    • Observation tools, such as Autism Diagnostic Observation Scale (ADOS)
  • How is autism diagnosed in adults?

    There's currently no standard procedure for confirming autism in adults. The best way to explore an autism diagnosis as an adult is to work with a neuropsychologist, psychiatrist, or another mental health professional, who will talk about your behavioral health history with you and use various screening tests, which may include IQ tests and autism-specific questionnaires, as well as other observation tools.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Hazlett HC, Gu H, Munsell BC, et al. Early Brain Development in Infants at High Risk for Autism Spectrum Disorder. Nature. 2017;542(7641):348–351. doi:10.1038/nature21369

  3. Centers for Disease Control and Prevention. Screening and diagnosis of autism spectrum disorder. Updated March 13, 2020.

  4. Asperger/Autism Network. Asperger/autism spectrum diagnosis in adults.

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