Doctors usually test for and diagnose autism in early childhood. However, as symptoms and severity can vary greatly, it can sometimes be difficult to diagnose.

Autism is a neurological condition that can cause differences in socialization, communication, and behavior. The diagnosis can look quite different, as no two autistic people are the same, and they may have varying support needs.

Autism spectrum disorder (ASD) is an umbrella term that encompasses three formerly separate conditions that are no longer considered official diagnoses in the current Diagnostic and Statistical Manual of Mental Disorders (DSM-5):

autistic disorder
pervasive developmental disorder, not otherwise specified (PDD-NOS)
Asperger syndrome

In the DSM-5, all of these diagnoses are now listed under the umbrella category of ASD. ASD levels 1, 2, and 3 indicate the level of support an autistic person may need.

Who has a greater chance of being diagnosed with autism?

According to the Centers for Disease Control and Prevention (CDC), about 1 in 26 children in the United States had ASD in 2020. Autism spectrum disorder occurs across all racial, ethnic, and socioeconomic groups.

It was thought to be about four times more common among boys than girls. However, recent research has indicated that since girls with ASD often present differently when compared with boys, they could be underdiagnosed.

Girls may mask their symptoms due to what’s known as the “camouflage effect.” Therefore, ASD may be more common in girls than previously thought.

There’s no known cure for ASD, and doctors haven’t discovered exactly what causes it, although we know genes play a role. Many people in the autistic community do not believe a cure is needed.

There may be many different factors that make a child more likely to have ASD, including environmental, biological, and genetic factors.

What are the symptoms of autism?

The early signs and symptoms of autism vary widely. Some children with ASD only have mild symptoms, and others have severe behavioral issues.

Toddlers usually like to interact with people and the environment they live in. Parents are typically the first to notice that their child is showing atypical behavior.

Every child on the autism spectrum experiences challenges and symptoms in the following areas:

communication (verbal and nonverbal)
social interaction
restricted or repetitive behaviors

It’s important to note that displaying one or more of these behaviors doesn’t necessarily mean that the child will meet the criteria for an ASD diagnosis.

These can also be attributed to other conditions or simply be considered personality traits.

How is autism diagnosed?

Doctors usually diagnose ASD in early childhood. However, because symptoms and severity vary greatly, autism spectrum disorder can sometimes be difficult to diagnose.

Some individuals aren’t diagnosed until adulthood.

At present, there’s no one official test for diagnosing autism. A parent or doctor may notice early indications of ASD in a young child, though a diagnosis would need to be confirmed.

If symptoms confirm it, a team of specialists and experts will usually make an official diagnosis of ASD. This could include a psychologist or neuropsychologist, a developmental pediatrician, a neurologist, and/or a psychiatrist.

Developmental screening

Starting from birth, a doctor will screen your child for developmental progress during routine and regular visits.

The American Academy of Pediatrics (AAP) recommends standardized autism-specific screening tests at 18 and 24 months of age in addition to general developmental surveillance.

If you’re concerned about your child’s development, a doctor may refer you to a specialist, especially if a sibling or other family member has ASD.

The specialist will conduct tests such as a hearing test to evaluate for deafness/difficulty hearing to determine if there’s a physical reason for the observed behaviors.

They’ll also use other screening tools, such as the Modified Checklist for Autism in Toddlers (M-CHAT).

The checklist is an updated screening tool that parents fill out. It helps determine a child’s chance of having autism as low, medium, or high. The test is free and consists of 20 questions.

If the test indicates that your child has a high chance of having ASD, they’ll receive a more comprehensive diagnostic evaluation.

If your child is at a medium chance, follow-up questions may be necessary to help definitively classify the results.

Comprehensive behavioral evaluation

The next step in autism diagnosis is a complete physical and neurologic examination. This may involve a team of specialists. The specialists may include:

developmental pediatricians
child psychologists
child neurologists
speech and language pathologists
occupational therapists

The evaluation may also include screening tools. There are many different developmental screening tools. No single tool can diagnose autism. Rather, a combination of many tools is necessary for an autism diagnosis.

Some examples of screening tools include:

Ages and Stages Questionnaires (ASQ)
Autism Diagnostic Interview — Revised (ADI-R)
Autism Diagnostic Observation Schedule (ADOS)
Autism Spectrum Rating Scales (ASRS)
Childhood Autism Rating Scale (CARS)
Pervasive Developmental Disorders Screening Test — Stage 3
Parents’ Evaluation of Developmental Status (PEDS)
Gilliam Autism Rating Scale
Screening Tool for Autism in Toddlers and Young Children (STAT)
Social Communication Questionnaire (SCQ)

Genetic testing

Though autism is known to be a genetic condition, genetic tests can’t diagnose or detect autism. There are many genes and environmental factors that can contribute to ASD.

Some laboratories can test for some of the biomarkers believed to be indicators for ASD. They look for the most commonly known genetic contributors, though this will rarely lead to any answers.

An atypical result on one of these genetic tests means that genetics probably contributed to the presence of ASD.

A typical result only means that a specific genetic contributor has been ruled out and that the cause is still unknown.

Takeaway

ASD is common and doesn’t have to be a cause for alarm. Autistic people can thrive and find communities for support and a shared experience.

But diagnosing ASD early and accurately is important to allow an autistic person to understand themselves and their needs, and for others (parents, teachers, etc.) to understand their behaviors and how to respond to them.

A child’s neuroplasticity, or ability to adapt based on new experiences, is greatest early on. Early intervention may reduce the challenges your child may experience. It also gives them the best chance for independence.

If needed, customizing therapies to meet your child’s individual needs can be successful in helping them live their best life. A team of specialists, teachers, therapists, doctors, and parents should design a program for each individual child.

In general, the earlier a child is diagnosed, the better their long-term outlook.

Data and statistics on autism spectrum disorder. (2024). https://www.cdc.gov/autism/data-research/?CDC_AAref_Val=https://www.cdc.gov/ncbddd/autism/data.html
Hyman SL, et al. (2020). Identification, evaluation, and management of children with autism spectrum disorder. https://publications.aap.org/pediatrics/article/145/1/e20193447/36917/Identification-Evaluation-and-Management-of?autologincheck=redirected
Maenner MJ, et al. (2023). Prevalence and characteristics of autism spectrum disorder among children aged 8 years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. https://www.cdc.gov/mmwr/volumes/72/ss/ss7202a1.htm?s_cid=ss7202a1_w
McCrossin R. (2022). Finding the true number of females with autistic spectrum disorder by estimating the biases in initial recognition and clinical diagnosis. https://pmc.ncbi.nlm.nih.gov/articles/PMC8870038/
Sauer AK, et al. (2021). Autism spectrum disorders: Etiology and pathology. https://www.ncbi.nlm.nih.gov/books/NBK573613/

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