How is Autism Diagnosed? Navigating the Autism Diagnosis Process

I didn’t always know my son was autistic. 

Reflecting, I’m surprised I didn’t pick up on symptoms with my background in pediatric nursing. But I was also a new mom and in the thick of dealing with a premature infant who spent nine weeks in the NICU. I was just trying to survive and consumed with helping my child to “catch up” on his developmental milestones. 

Looking back, there was always a reason to attribute a deficit towards…he was born at 28 weeks and four days, he just needs to catch up, he’s “normal” for his adjusted age, etc. While all those reasons could be true, it would take until my son was 3.5 years old before any diagnostic progress happened and until he was 4.5 before he was officially diagnosed with Autism Spectrum Disorder.

How Common is Autism Spectrum Disorder?

In March 2023, the CDC released a new prevalence report increasing the occurrence of Autism Spectrum Disorder (ASD) to one in 36 (2.6%) 8-year-olds as compared to the 2020 data findings of one in 44 8-year-olds. While there isn’t a direct cause or definitive explanation noted by the CDC, the suspicion surrounding the prevalence increase may be due to an increased awareness of ASD which is leading to more children being identified and diagnosed. 

While historically, White children, especially boys, have had higher rates of identification, children of other races and ethnicities have shown similar rates in recent research. The 2020 data reported White children at a rate of 2.4%, Black children at 2.9%, 3.2% of Hispanic children, and 3.3% of Asian/Pacific Islander children.

These percentages show that ASD is common across all groups of children but successful identification has been hindered (in the past and currently) by the need for accessible and equitable screening, support, and services for all children in all communities. 

The most recent 2023 report also examined the data reflecting cognitive ability revealing that 38% of children with autism had an intellectual disability with higher rates among Black children than White children. Currently, ASD in girls is slightly over 1% while the prevalence for boys remains four times higher.

Autism Signs and Symptoms

Therapy session

Early diagnosis and identification can assist a person in acquiring the support, services, and opportunities to live optimally.

However, the way an individual experiences autism is unique and defined by certain behaviors that occur along a spectrum, leading to varying degrees of challenges and strengths.

Signs of autism can be subtle or dramatic, each child is different. 

Autism can be diagnosed early in some children with some behaviors being noted as early as the first few months of life while some behaviors do not become clear until age 2 or 3 (or even later). It’s important to remember that some children without Autism Spectrum Disorder will show some similar behaviors, which is why it is important to have a professional evaluation. Below are some behaviors and milestones that should be reported to your pediatrician for further assessment.

By 6 Months

  • No big smiles, few smiles, or no otherwise engaging expressions
  • Limited to no eye contact

By 9 Months

  • Little to no smiles, facial expressions, or back-and-forth sharing of sounds

By 12 Months

  • Little to no babbling
  • Little to no gestures such as showing, pointing, waving, or reaching
  • Little to no response to name

By 16 Months

  • Little to no words

By 24 Months

  • Little to no meaningful, two-word phrases. Do not include imitating or repeating of phrases.

At Any Age

  • Loss of previously acquired skills such as babbling, speech, or social skills
  • Avoiding eye contact
  • Consist and persistent preference for solitude
  • Difficulty understanding others’ feelings
  • Delayed development of language
  • Repetition of words or phrases (echolalia-immediate or delayed)
  • Limited and restricted interests
  • Repetitive behaviors such as rocking, spinning, or flapping
  • Resistance to minor changes in routine/surroundings
  • Difficulty with transitions
  • Intense and unusual reactions to smells, tastes, sounds, textures, colors, and/or lights

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My Personal Experience

The interesting and complicating factor regarding ASD is how individualized and unique each person’s experience is. As the parent of an autistic child, I wish I could say that I fell in the camp where I picked up on symptoms immediately from birth and while I do notice small hints in past videos and memories, there was nothing to make me think my child was any different from any other child. Healthcare providers frequently commented on how my son did not appear to have been a premie. In my head, he was simply behind on his milestones as expected from being born premature by almost 12 weeks. 

I remember breathing a sigh of relief when he passed his second autism screener at a well-check. However, as we moved into toddlerhood and excited that he was close to being “caught up,” I began to feel inadequate as a mother. I felt like I was crazy, that I wasn’t a good mother because I couldn’t deal with my child like I saw other mothers parenting. I was convinced it was something wrong with me and it had nothing to do with my child. 

Then, the COVID-19 pandemic shut the entire world down. As lockdowns slightly lifted and the virus raged on, I was at my wits end with a 3-year-old at home. Something felt off but I couldn’t put my finger on it. I turned to my son’s past physical therapist for help. While I can’t remember exactly the type of symptoms I discussed with her at the time, she recommended I seek an occupational therapy evaluation. 

The OT evaluation revealed some answers with some sensory processing difficulties and a fine motor delay. It was after nearly a year of OT when my son’s therapist recommended we seek an autism evaluation. I was hesitant to pursue evaluation for various reasons such as not understanding what else the diagnosis would “give” us and not wanting a label given to my child. 

Despite my misgivings, the opportunity to have my son evaluated presented itself quite quickly, which is not always the case. After meeting with the psychologist, completing questionnaires, and my son completing his part of the evaluation, my husband and I sat on the couch in the psychologist’s office to be told what we already knew. There was no second-guessing this diagnosis and I felt relief more than anything. It wasn’t all in my head. I wasn’t crazy. My son is still the same person he was before his diagnosis, but now I understand why he was struggling.

The Diagnostic Process


I wish the diagnostic process were as simple as A to Z. Still, unfortunately, there can be many hoops, red tape, and typically lots of waiting throughout the process. The process is also not as streamlined as I wish it could be in the United States. Healthcare provider education, insurance requirements, wait lists, and accessibility are just a few of the issues that can impact the road to diagnosis. Each state in the U.S. is set up a bit differently, further complicating the matter. 

Many times, the first step is understanding that you have a concern regarding your child and advocating for them to be evaluated for that concern. Sometimes screening tools will highlight deficits that need to be further evaluated. A great place to start is by talking with your child’s pediatrician regarding your concerns. It would be helpful if you could bring any documentation or videos to show them concerning behaviors. 

In most cases, the pediatrician will be the starting point for the evaluation process including providing orders for therapy evaluations such as occupational therapy, physical therapy, speech therapy, or feeding therapy. These specialized evaluations can also highlight other deficits that may be missed in well-checks or screening tools. If therapy of any kind is warranted based on the results of the evaluation, it is a great place to start. 

Despite whether or not your child meets the criteria for ASD, if therapy is needed, it is my opinion that it should be pursued. Pediatricians may also refer to other healthcare providers who can diagnose ASD or who specialize in working with the autistic community such as psychologists and developmental pediatricians.

Screening Tools & Practices

Developmental and autism screenings are typically done in primary care pediatricians’ offices. The American Academy of Pediatrics recommends children be screened for disabilities and developmental delays during their well-child doctor visits specifically at 9, 18, and 30 months with additional screening if the child is at high risk (such as preterm birth or low birth weight). 

In addition to the developmental screenings, providers should specifically screen for ASD during well-child visits at 18 and 24 months (or more often if high risk including having a parent or sibling with ASD). Several screening tools can be used to look for developmental delays and autism including the Ages and Stages Questionnaires (ASQ), Communication and Symbolic Behavior Scales (CSBS), Parents’ Evaluation of Developmental Status (PEDS), Modified Checklist for Autism in Toddlers (MCHAT), and Screening Tool for Autism in Toddlers and Young Children (STAT). The CDC has assembled a great summary of many of these tools with accompanying links. You can find those here.

Who Can Diagnose?

Unfortunately, not every pediatric healthcare provider can diagnose autism and for those who do have the basic training in autism, many do not have the specialized training required to be able to assess, diagnose, or use specialized assessment tools to do so. While it is possible to receive a diagnosis from a pediatrician, typically pediatricians prefer to refer for specialized assessment and care to developmental/neurobehavioral pediatricians, clinical psychologists, child psychiatrists, or child neurologists. Other providers such as geneticists, occupational therapists, speech therapists, or early intervention programs may have the expertise to diagnose as well.

Assessment and evaluation is a lengthy process requiring patient observation, interviews with the patient, teachers, caregivers, or other important adults, specific autism assessment tools in addition to cognitive and language ability tests.

Diagnostic Criteria

The diagnostic criteria for Autism Spectrum Disorder (ASD), are crafted by the American Psychiatric Association and consistently updated in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5). This manual serves as the standard reference guide for healthcare and mental health providers to diagnose ASD. The diagnostic criteria are thorough and precise, therefore, the following criteria is a summary. The DSM-5 focuses mainly on two major categories of symptomatology with detailed qualifiers: deficits in social communication/interaction and restrictive, repetitive patterns of behaviors, interests, or activities. 

A person (adult or child) must possess persistent deficits in social communication and social interactions across various parts of their life. This could manifest as a failure of normal back-and-forth conversations, reduced affect or emotion, reduced sharing of interests, or failure to respond or initiate social situations. Deficits in nonverbal communication behaviors such as abnormal eye contact or body language, difficulty understanding facial expressions and nonverbal communication, and difficulty understanding gestures. Difficulty in developing and maintaining relationships such as difficulty in making friends or sharing imaginative play or an absence of interest in peers. 

These criteria however are meant to illustrate to a practitioner how these social deficits may manifest but are not meant to be exhaustive. ASD is different in each child and your child may display difficulties of varying degrees in other areas.

Restricted and repetitive patterns of behavior, activities, or interests must manifest in at least two areas, either currently or historically.

  1. Repetitive motor movements, use of an object, or speech pattern. This can look like lining up toys, echolalia, or hand/arm flapping.
  2. Insisting upon sameness or inflexibility with routines. This appears as severe distress with small changes to routines, difficulties with transitions, rigid (black and white) thinking, or needing to eat the same foods every day.
  3. Interests that are restricted or lead to fixation in abnormal intensity or focus such as only playing with one toy, strong attachment, or preoccupation with an item or personal.
  4. Hyperreactivity or Hyporeactivity to sensory input. Sensory differences can manifest in varying degrees and types from hyper-sensitivity or hypo-sensitivity to pain or temperature, avoidance of loud sounds or textures, visual fascination with objects or stimuli, craving movement or deep pressure, or avoiding movement or deep pressure.

In addition to the two major categories, three additional criteria statements must be met. Firstly, the symptoms as noted above MUST be present in the early developmental period. However, it is understood that some symptoms may not fully manifest until the social demands exceed an individual’s capacity and individuals may adapt by masking using learned strategies. Secondly, the symptoms must cause “clinically significant impairment in social, occupational, or other important areas of current functioning.”

Lastly, the symptoms are not explained by another diagnosis such as an intellectual disability or a global developmental delay. However, it is important to note intellectual disability and ASD frequently co-occur. To diagnose both as co-occurring, social communication must be below what is expected for their general developmental level.

It is important for a diagnostician to also specify the severity of symptoms and other quantifiers such as if the ASD diagnosis is accompanied by an intellectual impairment, language impairment, is associated with another neurodevelopmental/mental/behavioral disorder, catatonia or can be tied to a known medical or genetic condition or environmental factor.

Severity is categorized by levels and can be specified in each category (social communication and restricted/repetitive behaviors). Level 3 is described as requiring very substantial support with level 2 requiring substantial support and level 1 requiring support. In the table below are some examples of support needed for various levels broken down into social communication and restricted/repetitive behavior categories.

Severity Levels

Severity LevelSocial CommunicationRestricted/Repetitive Behaviors
Level 3
“Very substantial support”
• Severe deficits in verbal and nonverbal social communication.
• Very limited initiations of social interactions, minimal response to social overtones.
• Very few words of intelligible speech, rare initiation of interactions, or unusual approaches.
• Inflexible behavior, extreme difficulty coping with change.
• Restricted and/or repetitive behaviors that markedly interfere with functioning in all areas.
• Great distress and difficulty in transitioning or changing focus.
Level 2
“Substantial support”
• Marked deficits in social communication (verbal and nonverbal)
• Social impairments despite support in place.
• Limited initiation of social interactions or abnormal responses to social interactions.
• May use simple sentences, interactions may be limited to special interests.
• Inflexible behavior, and difficulty coping with change.
• Repetitive or restricted behaviors that occur frequently enough to be obvious to casual observers while interfering with all areas of functioning.
• Distress is noted when changing focus or transitioning.
Level 1
• Without support, deficits in social communication cause noticeable impairments.
• Difficulty initiating social interactions, atypical or unsuccessful responses in social situations.
• Decreased interest in social interactions.
• May use full sentences but may struggle with back-and-forth conversations.
• Attempts to make friends can be viewed as odd and usually are unsuccessful.
• Inflexible behavior that significantly interferes with functioning in one or more contexts.
• Difficulty transitioning between activities, problems with organization and planning.

Diagnostic Tools


Many tools can be used to assess ASD but it is important to remember that no single assessment or tool should diagnose your child. It is important for the healthcare provider assessing your child to use multiple sources of information such as parent, caregiver, or teacher descriptions of behavior or development. More perspectives lead to more information that can assist a practitioner in their assessment. 

In addition to using the diagnostic criteria found in the DSM 5, providers may use diagnostic tools such as the Autism Diagnosis Interview-Revised (ADI-R), Autism Diagnostic Observation Schedule-Generic (ADOS-G), Childhood Autism Rating Scale (CARS), and Gilliam Autism Rating Scale-Second Edition (GARS-2). For a more in-depth description of the most popular tools with links to each, please visit the CDC’s web page at this link.

Why Seek A Diagnosis?

Seeking a diagnosis can be nerve wracking but beneficial for your child medically, educationally, and socially. Appropriate assessments can help the child, caregivers, and healthcare providers understand why the child is experiencing certain difficulties and how best to help. An accurate diagnosis also helps to prevent misdiagnoses and assists in addressing other medical or mental health issues that are present in the future. 

With a diagnosis, a child can gain access to necessary services and benefits such as Occupational therapy, Speech therapy, ABA therapy, SSI/disability benefits, Medicaid eligibility, or insurance coverage of services. Diagnoses also entitle your child to adjustments and accommodations at school and for their educational goals. As children get older, they will be able to request accommodations in their work life based on their diagnoses. 


There is a wealth of knowledge available online to assist you in your child’s journey towards diagnosis. Part of advocating for your child can be conducting your research to find how best to help them. Below are just a few of the resources available.

Autism Speaks

American Academy of Pediatrics Screening Tool Finder

CDC Autism Spectrum Disorder Webpage

​​American Academy of Pediatrics Autism Page 

The Autism Society

AAP Practice Guidelines for Autism Spectrum Disorder

Healthy Children-How Doctors Screen for Autism

American Psychiatric Association ASD Webpage

Autism Speaks/DSM 5 Diagnosis Criteria

Where To Go From Here

Navigating the process of an autism diagnosis is challenging, lengthy, and not something a parent/caregiver can do alone. It truly takes a village. Your village will be filled with medical providers, therapists, and educators who will assist your child in living their best life. Autism involves diverse experiences and challenges, therefore your child’s team will be as unique as they are. 

Each therapy, medication, or accommodation should be tailored for your child to be their most successful. Remember, YOU are the expert on your child and the best advocate they could have. Your child is the same person they were before diagnosis except now their parent has a better perspective to assist and interact with them. Keep going. Diagnosis is worth the journey.

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