Autism spectrum disorder (ASD) is diagnosed when a person shows persistent difficulties in social communication and interaction, combined with restricted or repetitive patterns of behavior. The current diagnostic standard in the United States, the DSM-5-TR, requires deficits in all three areas of social communication plus at least two of four types of repetitive behaviors. About 1 in 31 children in the U.S. are now identified with autism, based on 2022 surveillance data from the CDC.
The Two Core Categories
An autism diagnosis rests on two pillars. The first is social communication and interaction. The second is restricted, repetitive behaviors. Both must be present. A person who struggles socially but doesn’t show repetitive behaviors or intense fixed interests wouldn’t meet the criteria, and vice versa. This two-category structure is used by both the DSM-5-TR (the manual used in the U.S.) and the ICD-11 (the international system used in much of the rest of the world).
Social Communication: All Three Areas Required
The DSM-5-TR requires deficits in all three of the following areas, not just one or two. This was clarified in the 2022 text revision, which updated the wording from “as manifested by the following” to “as manifested by all of the following” to prevent misinterpretation.
Social-emotional reciprocity refers to the natural back-and-forth of social interaction. This can look like difficulty holding a two-way conversation, reduced sharing of emotions or interests, or not initiating or responding to social exchanges. In younger children, it might mean not actively joining in simple social play or involving other people only as tools to get something rather than as social partners.
Nonverbal communication covers the body language, facial expressions, eye contact, and gestures people use alongside words. Someone might have limited facial expressions, unusual eye contact, difficulty coordinating gestures with speech, or trouble reading these signals in others. The range is wide: some people show subtle mismatches between their words and body language, while others use very little nonverbal communication at all.
Building and understanding relationships includes difficulty adjusting behavior for different social settings, trouble making or keeping friends, challenges with imaginative play (in children), or a reduced interest in peers. This doesn’t mean a person has no desire for connection. It means the skills involved in navigating relationships are harder to develop or maintain.
Repetitive Behaviors: At Least Two of Four Types
The second category requires at least two of the following four types of behavior, either currently or at some point in the person’s history.
- Repetitive movements, speech, or use of objects. Common examples include hand flapping, body rocking, toe walking, spinning objects, lining up toys in rows, or repeating phrases (sometimes called echolalia). Some people fixate on parts of objects, like spinning car wheels or watching a fan blade.
- Insistence on sameness and rigid routines. This can show up as extreme distress over small changes, difficulty with transitions, needing to take the same route every day, eating the same foods, or following greeting rituals. Rigid thinking patterns also fall here.
- Intensely focused interests. The interest itself might be ordinary (trains, weather, a TV show), but the intensity or narrowness of focus is unusual. A child might memorize every detail about a topic to the exclusion of everything else, or become deeply attached to an unusual object.
- Unusual sensory responses. This includes being over-sensitive or under-sensitive to sound, texture, temperature, or pain. A person might cover their ears at sounds others barely notice, seek out specific textures obsessively, or seem indifferent to temperature changes. Visual fascination with lights or movement also counts.
Onset and Timing
Symptoms must be present during the early developmental period, though they don’t need to be recognized that early. Many children show signs by 12 to 18 months, but most aren’t diagnosed until after age 3. Some children experience regression between ages 1 and 2, losing language, play skills, or social behaviors they’d previously developed.
The criteria also acknowledge that symptoms may not become fully apparent until social demands exceed a person’s capacity to cope. A bright child might manage well in a small, structured preschool but struggle when the social complexity of elementary school increases. This is especially relevant for people diagnosed later in life.
How Severity Levels Work
The DSM-5-TR assigns one of three severity levels based on how much support someone needs. Level 1, “requiring support,” describes someone who can speak in full sentences and wants social connection but struggles with the flow of conversation and organizing daily life without help. Level 2, “requiring substantial support,” describes more noticeable difficulties in verbal and nonverbal social skills, with restricted behaviors that are obvious to casual observers. Level 3, “requiring very substantial support,” describes people with very limited speech and social initiations, along with repetitive behaviors that significantly interfere with daily functioning.
The ICD-11 takes a different approach and does not include severity levels. Its designers considered the severity metric to have questionable validity, partly because some autistic people function well in many settings through exceptional effort, masking the extent of their underlying difficulties.
How Clinicians Evaluate the Criteria
There’s no blood test or brain scan for autism. Diagnosis relies on behavioral observation and developmental history. The gold standard tools are the Autism Diagnostic Observation Schedule (ADOS-2) and the Autism Diagnostic Interview-Revised (ADI-R). The ADOS-2 is a semi-structured assessment where a clinician directly observes the person over 40 to 60 minutes, looking at social and communication behaviors in real time. The ADI-R is a detailed interview with a parent or caregiver about the person’s developmental history. Another widely used tool, the Childhood Autism Rating Scale (CARS-2), uses 15 items rated by a clinician based on both caregiver interviews and direct observation.
Clinicians combine information from these tools with developmental history, school reports, and sometimes input from multiple professionals (psychologists, speech therapists, pediatricians) to determine whether the diagnostic criteria are met.
Diagnosis in Adults
The same core criteria apply to adults, but evaluating them looks different. An adult assessment focuses on whether the social communication difficulties and repetitive behaviors have been present since childhood and continue into the present, even if they were never formally identified. Clinicians look for a potential gap between intellectual ability and everyday functioning. Someone might perform well on IQ measures but struggle significantly with planning, daily routines, or holding employment.
A major complication in adult diagnosis is masking, where a person has learned to camouflage their difficulties through conscious effort. The ICD-11 explicitly recognizes this: a diagnosis is still appropriate when someone can function adequately in many contexts only through exceptional effort. Assessments for adults are often adapted in pacing, setting, and duration to account for sensory or communication needs. Many autistic adults go undiagnosed for decades, particularly women and people without intellectual disability, because their presentations don’t match stereotypical expectations.
Who Gets Diagnosed
Autism is diagnosed roughly 3.4 times more often in boys than girls. The most recent CDC data from 2022 found prevalence of about 49 per 1,000 among boys compared to 14 per 1,000 among girls. Prevalence also varies across racial and ethnic groups: Black, Hispanic, American Indian/Alaska Native, and Asian/Pacific Islander children are now identified at higher rates than White children, a reversal from earlier years that likely reflects improved screening access rather than true differences in occurrence. Overall U.S. prevalence has risen from about 1 in 150 children in 2000 to 1 in 31 in 2022, driven largely by broader criteria, better awareness, and expanded screening rather than an increase in the underlying condition.