How Autism Is Diagnosed

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There is no easy medical test to diagnose autism. The process includes interviews, observation, and evaluations of 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, early treatment, and, with luck, a positive outcome. If autism is ruled out, other challenges may be caught and addressed sooner rather than later.

Even if autism is diagnosed and treated later in childhood—or in adulthood—treatments and support can make a big and positive difference.

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If you think that you or someone you love may have autism, you probably have noticed certain symptoms. Perhaps you've picked up on a lack of eye contact, difficulty with social relationships, speech delays, or odd physical behaviors such as rocking, finger flicking, or toe-walking.

It can be helpful to reference an autism symptoms checklist.

Older children and adults may have some or all of the symptoms seen in younger children. Most of the time, however, these symptoms are relatively mild; late diagnosis means that the individual has managed to compensate for autistic challenges.

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

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

Others' Observations

Aside from parents, teachers are often the first to note signs of autism. Though they may be familiar with them through working with many children, remember that a teacher cannot and should not make a diagnosis. The same is true of friends and relatives who may believe they see signs of autism in your child.

While it's fine to take their concerns seriously enough to schedule an appointment with a health professional, their "diagnosis" should never be the final word.

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 seeking a diagnosis will usually see a psychologist or psychiatrist. Your choice will, to a large degree, depend on who is available in your local area. Whatever their specialty, be sure that the expert you choose has experience with and knowledge of autism spectrum disorders.


Autism cannot currently be diagnosed with a medical test, though steps toward developing diagnostic tests are in motion. For example, in their Children's Autism Metabolome Project (CAMP) study, researchers from UC Davis MIND Institute and NeuroPointDX showed a metabolic blood test could detect Autism in 17% of kids.

Currently, however, 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 in an age-appropriate and meaningful manner
  • Occupational therapy evaluations (tests to check for age-appropriate fine motor skills, 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, for parents to fill out about their child's developmental milestones, behaviors, sensitivities, challenges, and strengths
  • Other tests, such as the Autism Diagnostic Observation Scale (ADOS) and the Checklist for Autism in Toddlers (CHAT), which examine observations of children's behaviors based on norms

None of these tests are perfect and some can, in fact, be misleading. IQ and speech tests, for example, are written for typically-developing children, but 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 definitive. It's not unusual to hear (particularly of a very young child), "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?" While this kind of uncertainty can be extremely frustrating, it's sometimes unavoidable.


Currently, there are no diagnostic imaging tests for autism spectrum disorder. However, there is considerable research on detecting autism early through the use of brain scans. These studies include structural magnetic resonance imaging (MRI) scans and functional connectivity MRI scans. These studies have mostly been done on infants who have a sibling who has autism and are, therefore, at greater risk.

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

Differential Diagnoses

In many cases, children have developmental challenges that resemble autism but which turn out to be simple delays or signs of other developmental issues. For example, not responding to a name could very well be a symptom of hearing impairment. Late talking could be due to aphasia or apraxia of speech.

A child could also have a learning disability, attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder, narcissistic personality disorder, oppositional defiant disorder, or hyperlexia. This might be the correct diagnosis, or 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 people in the general population.

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 navigating the road ahead.

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  1. Smith AM, King JJ, West PR, et al. Amino acid dysregulation metabotypes: Potential biomarkers for diagnosis and individualized treatment for subtypes of autism spectrum disorder. Biol Psychiatry. 2019;85(4):345-354. doi:10.1016/j.biopsych.2018.08.016

  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

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