CDC autism signs: social communication and repetitive behaviors explained

Last updated 2026-07-09

Autism, as the CDC and the DSM-5 define it, comes down to two things happening together: lasting differences in how someone communicates and connects socially, and restricted or repetitive behaviors and interests. Signs can appear in the first year of life. About 1 in 36 children in the U.S. is diagnosed with autism, and finding support earlier tends to lead to better outcomes.

What autism means, according to the CDC

The CDC describes autism spectrum disorder (ASD) as a "developmental disability caused by differences in the brain" that affects communication, interaction, behavior, and learning. ^[1] It's careful not to pin autism to one fixed picture: it's a spectrum, and it looks different from one child to the next.

The clinical definition most doctors work from comes from the DSM-5, published by the American Psychiatric Association. To meet criteria, a child needs persistent difficulties with social communication and interaction across more than one setting, plus restricted or repetitive patterns of behavior, interests, or activities. Both have to show up together. A child who only shows repetitive behaviors, without differences in social communication, wouldn't meet full criteria. ^[2]

Symptoms need to trace back to early development, even if they don't become obvious until social demands outpace what the child can handle, and they have to cause real difficulty in daily life. That last part matters, because many autistic people build coping strategies that mask symptoms at school or in other structured settings. It's part of why girls and women have historically been underdiagnosed.

The CDC's latest numbers, from the Autism and Developmental Disabilities Monitoring (ADDM) Network's 2020 surveillance data, put the rate at 1 in 36 children aged 8. ^[1] That's up from 1 in 44 in the 2018 data, and researchers are still sorting out how much of that rise reflects better awareness and broader diagnostic criteria versus an actual increase in prevalence.

The two symptom domains behind every sign you'll read about

The DSM-5 sorts every autism sign into one of two buckets, and that framing is what makes the long, overwhelming lists you find online actually make sense.

The first domain is social communication and interaction, and it breaks into three parts. One is difficulty with the back-and-forth of social exchange: sharing interests or emotions, starting or responding to interactions. A toddler who doesn't point to show you something interesting, or doesn't look at you when you name an object, is showing an early version of this. Another part is nonverbal communication, things like eye contact, facial expressions, and gestures. Autistic children may use fewer of these, use them differently, or struggle to read them in other people, including moments where verbal and nonverbal signals don't line up (a child saying "yes" while shaking their head no, with no sense that anything's off). The third part is difficulty developing and understanding relationships: adjusting behavior for different social settings, engaging in imaginative play, making friends, or showing interest in peers.

The second domain covers restricted or repetitive behaviors and interests, and a diagnosis requires at least two of four patterns: repetitive movements, use of objects, or speech (hand flapping, lining up toys, echolalia); insistence on sameness and rigid routines; unusually intense or narrow interests; and over- or under-reactivity to sensory input, like strong reactions to sound, texture, or pain. ^[2]

DSM-5 also assigns severity levels, 1 through 3, but these describe how much support someone needs, not how "autistic" they are. Level 3 means very substantial support is needed; Level 1 means some support is needed. People often read these as a ranking of who's "more" or "less" autistic, but that's not what they're for.

Early signs in babies and toddlers

Most signs become noticeable between 12 and 24 months, though eye-tracking research suggests subtle differences in social attention can show up as early as 2 to 6 months in some infants. ^[3]

The CDC lists these as specific early signs to watch for: ^[11]

• Not responding to their name by 9 months
• Not showing facial expressions like happy, sad, or surprised by 9 months
• Not playing simple interactive games like pat-a-cake by 12 months
• Using few or no gestures by 12 months (no pointing, waving, or reaching)
• Not sharing interest by showing objects by 15 months
• Not noticing when others are hurt or upset by 24 months
• Not engaging in pretend play by 30 months

The CDC also flags regression: some children develop language and social skills on schedule, then lose them, usually between 15 and 24 months. Losing speech or social behaviors is a reason to get an evaluation right away, not something to wait out.

No single sign, on its own, means a child has autism. Late walking, limited eye contact, a preference for solitary play: each of these can have plenty of other explanations. Clinicians look for a pattern across several areas and settings, not one item on a checklist. If concerns about communication show up alongside these social signs, early intervention services can often start before a formal diagnosis is even in place.

What restricted and repetitive behavior looks like day to day

The clinical language sounds abstract, so here's what it tends to look like in practice.

Repetitive body movements, often called stimming in autistic communities, can help a child self-regulate: hand flapping, rocking, spinning, flicking fingers near the face. These tend to show up more when a child is excited, anxious, or overwhelmed, and many autistic adults describe stimming as calming rather than distressing. It becomes a clinical concern when it interferes with learning or causes injury, not simply because it looks unusual.

Insistence on sameness shows up in ways parents don't always connect to autism at first: a complete meltdown over taking a different route home, eating only foods of a certain color or texture, needing the exact same bedtime script every night, real distress when furniture gets moved. The distress in these moments is genuine and often intense, not exaggerated.

Fixated interests look like an unusually deep, narrow focus on one topic. Plenty of kids go through a dinosaur phase or a train phase; with autism, the intensity and exclusivity are different. The child wants to talk only about that topic, knows an extraordinary amount of detail, and may struggle to hold a conversation about anything else.

Sensory differences are now formally part of DSM-5 criteria, which wasn't true in older diagnostic systems. A child might gag at certain food textures, cover their ears at sounds that don't strike anyone else as loud, seek out deep pressure constantly, or seem unbothered by pain that would stop most kids cold. Both over- and under-sensitivity count.

Echolalia, repeating words or phrases heard from other people or from media, is one of the most common speech patterns in autism. It can happen right away (repeating something just said) or after a delay (a line from a cartoon heard weeks earlier). Echolalia isn't meaningless; in many children it does real communicative work, and understanding that early is one of the more useful things a parent can learn.

How the signs shift with age

Autism doesn't look the same at 18 months as it does at 5 years or at 12. The underlying differences stay, but how they show up changes as social demands increase.

Worth sitting with: many autistic people, especially those with strong verbal skills and average or above-average IQ, aren't diagnosed until their teens or adulthood. The CDC's surveillance system historically undercounts this group, since school records and administrative data don't always catch high-masking individuals. ^[1]

For a school-age child who's been talking for years, a new concern like apraxia can muddy the picture further. Apraxia of speech and autism can occur together, and telling them apart matters for how speech therapy gets structured.

How is autism diagnosed, and who does the evaluation?

There's no blood test or brain scan for autism. Diagnosis rests on watching how a child behaves, learning their developmental history, and running standardized assessments.^[4]

The two tools you'll hear about most are the ADOS-2 (Autism Diagnostic Observation Schedule, Second Edition) and the ADI-R (Autism Diagnostic Interview, Revised). The ADOS-2 is a structured session with the child; the ADI-R is a structured interview with parents. Neither is mandatory, but used together they're considered the research standard.

Evaluations are typically done by developmental pediatricians, child psychologists, neuropsychologists, or multidisciplinary teams at children's hospitals and university clinics. Speech-language pathologists are frequently part of that team, especially when communication is the central concern, and ASHA considers SLPs essential to autism assessment.^[5]

The wait for a full evaluation is often long, 6 to 18 months in many U.S. communities, longer still in rural areas. Some families go private instead, which can run $2,000 to $5,000 out of pocket depending on location and provider. Telehealth has widened access somewhat, though in-person observation remains the standard for young children.

You don't have to wait for a diagnosis to start early intervention. Under IDEA, children under 3 with developmental delays are entitled to a free evaluation through their state's early intervention program, diagnosis or not.^[6] Past age 3, similar rights kick in through the school district's special education evaluation process.

How common are these signs, really?

The CDC's ADDM Network is the main source for U.S. prevalence numbers. Its 2023 report, based on 2020 data from 11 communities, found autism in 1 in 36 eight-year-olds, about 2.8%.^[12] Boys were diagnosed at a higher rate (1 in 23) than girls (1 in 76), though that gap almost certainly says more about diagnostic bias than any real difference between sexes.

The median age of first diagnosis in that data was 49 months, just past 4 years old, even though most researchers agree accurate diagnosis is possible by age 2 to 3 using tools like the ADOS-2.^[4] The CDC has been trying to push that median down to 36 months or younger.

Race and income still shape who gets diagnosed and when. White children continue to be diagnosed at higher rates than Black, Hispanic, and Asian children in the 2023 ADDM data, despite research suggesting autism shows up at similar rates across groups. Access to care, clinician bias, and language barriers all play a part.

About 38% of autistic children also have an intellectual disability, while roughly 44% have average or above-average IQ, per ADDM surveillance.^[1] Those numbers matter because they shape what support looks like and what's realistic to expect.

Autism or just a speech delay?

Pediatricians hear this question all the time, and the honest answer is that it's messy, because the two frequently overlap.

A speech or language delay just means a child's communication trails typical milestones. Plenty of things cause that: hearing loss, being a late talker with no underlying neurological difference, apraxia of speech, selective mutism, developmental language disorder. Autism is one possible cause among several, not the only one.

The real dividing line is social communication. A late talker who makes good eye contact, points to share interest, plays back and forth, and reads emotion well is less likely to be autistic than a child with similar speech delays who doesn't do those things. That's a pattern, not a guarantee: some autistic kids have strong eye contact, and some late talkers show very limited social engagement.

Speech-language pathologists are often the first to raise autism as a possibility, simply because they're watching communication so closely. Speech therapy for autism doesn't look like therapy for a straightforward articulation delay. When autism is part of the picture, the work shifts toward functional communication and pragmatics (the social rules of language), and often toward augmentative and alternative communication. AAC devices are increasingly a first-line choice for nonspeaking or minimally speaking autistic children, not something to try only after everything else fails.

When a child's motor speech difficulties are significant on top of social communication differences, it's worth getting them evaluated for childhood apraxia of speech. CAS and autism can look very similar in some kids, and they call for different intervention approaches.

What actually helps

Some approaches to autism support have real evidence behind them. Others are marketed aggressively with little or nothing to back them up, and it's worth knowing which is which.

Applied Behavior Analysis (ABA) is the most researched intervention for autism, with decades of studies behind it, but it remains controversial in autistic communities, partly for historical reasons and partly because quality varies so much from provider to provider. ASHA and the AAP currently agree that high-quality, naturalistic, child-led ABA can support communication and adaptive skills, while the older intensive discrete-trial format with aversives is no longer acceptable practice.^[5]

Speech-language therapy is recommended for nearly every autistic child with communication differences, though the approach depends on the individual child. For nonspeaking children, autism spectrum speech therapy now tends to build AAC in from the beginning instead of waiting to see if speech develops first. ASHA's position is that AAC should start early and should never be held off on the theory that it might undercut motivation to speak: the evidence doesn't support that worry.^[5]

Social communication programs like ESDM (Early Start Denver Model) and JASPER have a growing evidence base for young children. Both are naturalistic and play-based; ESDM has been studied in children as young as 18 to 30 months and shows effects on language and adaptive behavior.^[7]

Occupational therapy helps with sensory processing differences and daily living skills, and many autistic children benefit from it, particularly when sensory reactivity gets in the way of eating, dressing, or participating in class.

For something more flexible and lower-barrier, the Little Words app offers a speech companion built around the communication patterns of neurodivergent kids, autism included. It won't replace a speech-language pathologist, but it can carry practice into everyday moments that structured therapy sessions don't always reach.

One thing genuinely not worth the money: facilitated communication, where a facilitator supports a person's hand or arm while they type. Controlled studies have shown the output reflects the facilitator's thoughts rather than the autistic person's, and major professional bodies, including ASHA, have spoken out against it.^[5]

If you think your child is showing signs

Start with your pediatrician, but don't stop there. The American Academy of Pediatrics recommends autism-specific screening at 18 and 24 months using validated tools like the M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up).^[8] Ask for it if your pediatrician hasn't already done it. A positive screen means the next step is a referral for a full developmental evaluation.

At the same time, request an early intervention evaluation. Every U.S. state entitles children from birth to age 3 to a free multidisciplinary evaluation under IDEA Part C, and to free services if they qualify, no diagnosis needed. Call your state's early intervention program directly rather than waiting on a pediatrician referral, which just adds weeks you don't need to lose.^[6]

It also helps to keep a short video diary. Clinicians only see your child in one setting for a short time, and a 30-second phone clip of a repetitive behavior or an unusual communication pattern is often more useful during an evaluation than a detailed description ever could be.

Look for a parent advocate or family support organization in your state. The Autism Society of America and the Autism Science Foundation both maintain state and local resource directories. They don't perform evaluations, but they can walk you through the process and explain your rights under IDEA. For older children and teens newly suspected of being autistic, online speech therapy has become much more accessible since 2020, and some providers now specialize in working with late-identified autistic people.

Are autism signs different in girls and women?

They are, and clinical practice is still catching up to what the research shows. Autistic girls are more likely to camouflage or mask their social differences, learning to mimic neurotypical behavior well enough to slip under the radar. They may gravitate toward social topics like relationships or celebrities, which reads as more typical than, say, a fascination with train schedules, and they'll often push themselves to follow social scripts even when those scripts don't come naturally.^[9]

The upshot is that girls get diagnosed later, get misdiagnosed with anxiety or ADHD, or don't get diagnosed at all. The CDC's ADDM data puts the male-to-female ratio at roughly 3.8 to 1 among diagnosed cases, but many researchers think the real ratio is closer to 2 to 1, maybe lower.^[9]

Masking isn't free. Autistic people who mask heavily report much higher rates of anxiety, depression, and burnout, and the exhaustion of performing neurotypicality tends to build over time rather than ease off.

If a girl is struggling socially, running high anxiety, or showing rigid thinking alongside intense interests that don't fit the "typical" autism picture, it's worth asking the question directly instead of ruling it out just because she makes good eye contact.

What should parents know about sensory differences in autism?

Sensory processing differences didn't formally enter the diagnostic criteria for autism until the DSM-5 in 2013, which surprises a lot of people. Before that, doctors tended to treat sensory issues as a side note rather than a core part of the picture.

The CDC now lists sensory symptoms directly as part of the autism profile: apparent indifference to pain or temperature, adverse responses to specific sounds or textures, excessive smelling or touching of objects, and visual fascination with lights or movement.^[1]

Research reviewed in the Journal of Autism and Developmental Disorders puts the share of autistic individuals with some degree of atypical sensory processing at 70 to 96%, though the number moves depending on how sensory differences are measured and who's being studied.^[10]

Hypersensitivity and hyposensitivity often show up in the same child at once. The kid who can't stand a tag in their shirt might not notice a real injury. That combination confuses parents, and it trips up teachers who mistake sensory meltdowns for defiance.

Occupational therapists who specialize in sensory integration are the main resource here. Sensory diets, changes to the physical environment, and gradual desensitization all have some evidence behind them, though the research on sensory integration therapy specifically is more mixed than its popularity suggests. It's worth asking a therapist what approach they use and what the evidence looks like for your child in particular.

Common questions parents ask

What age do autism signs usually appear?

Most signs show up between 12 and 24 months, and the CDC recommends watching for specific red flags starting at 9 months. Some children seem to develop typically and then lose skills, usually between 15 and 24 months, and that kind of regression is itself a significant red flag. Eye-tracking studies suggest subtle differences in social attention may be detectable even earlier, in the first few months of life, though those tools aren't used in clinics yet.

Can a child have autism without a speech delay?

Yes. Plenty of autistic people develop speech right on schedule, or even early. The social communication differences in autism go beyond talking: reading nonverbal cues, catching implied meaning, adjusting language to fit the situation, and holding up a back-and-forth conversation. A child who talks constantly but struggles to take turns, read sarcasm, or notice what others are interested in can be autistic with no speech delay in their history at all.

Is echolalia a sign of autism?

Echolalia, repeating words or phrases picked up from other people or from media, shows up a lot in autism but isn't unique to it. Typically developing toddlers go through a normal echolalia phase too. In autism it tends to stick around longer and often does specific communicative work, like borrowing a familiar phrase to express a feeling. If it's still the dominant way a child communicates after age 2 or 3, that's worth an evaluation, but on its own it doesn't tell you much.

What's the difference between Level 1, Level 2, and Level 3 autism?

These DSM-5 labels describe how much support someone currently needs, not a ranking of how "severe" their autism is. Level 1 means requiring support, Level 2 means requiring substantial support, Level 3 means requiring very substantial support. Needs shift across settings and over time, so someone might sit at Level 1 in a familiar environment and need far more support somewhere new or demanding. The levels aren't a measure of who's "more" autistic.

Do autistic children always have intellectual disabilities?

No. CDC ADDM data from 2020 found about 38% of autistic children also have an intellectual disability (IQ below 70), while about 44% have average or above-average IQ, and the remaining 18% or so land in a borderline range. The idea that autism always comes with intellectual disability, or never does, is wrong either way. It spans the full range of intellectual ability, and support needs don't line up neatly with IQ.

How do I get my child evaluated for autism?

Start with your pediatrician and ask for a screening using the M-CHAT-R/F at 18 and 24 months, per AAP recommendations. If that flags concerns, ask for a referral to a developmental pediatrician, psychologist, or multidisciplinary autism team. At the same time, reach out directly to your state's early intervention program (for kids under 3) or your school district (for kids 3 and up). Under IDEA you're entitled to a free evaluation, and you don't need a doctor's referral to request one.

Can girls have autism without obvious signs?

Yes. Autistic girls are significantly more likely to mask their social differences, imitating neurotypical behavior closely enough to avoid diagnosis. Intense social interests, strong mimicry, and enough rule-following to look fine in structured settings can all cover what's underneath. That leads to later diagnosis, misdiagnosis with anxiety or ADHD, and higher rates of mental health struggles from the effort of keeping the mask on. Clinicians are more aware of this pattern now, but girls are still underidentified at high rates.

What causes autism?

There's no single identified cause. The scientific consensus points to a mix of genetic and environmental factors. Large genetic studies have turned up hundreds of genes linked to autism risk, and researchers have also looked at advanced parental age, certain prenatal exposures, and very preterm birth as environmental factors. Vaccines do not cause autism: that claim traces back to a 1998 study that was fully retracted for data fraud, and multiple large studies covering millions of children have found no link.

What is stimming and should I try to stop it?

Stimming refers to self-stimulatory behavior: repetitive movements like hand flapping, rocking, or spinning that often help a child regulate themselves. Many autistic adults say stimming is essential for handling sensory overwhelm, excitement, or anxiety. Trying to suppress it without addressing what's driving it usually isn't recommended and can make things worse. The exception is a behavior that risks injury, and in that case an occupational therapist can help find a safer alternative that does the same job.

How is autism different from ADHD?

ADHD and autism overlap in some ways, including attention difficulties, impulsivity, and social struggles, and by some estimates they co-occur in 50 to 70% of cases. What sets autism apart is the specific pattern of social communication deficits (not just inattention getting in the way socially) along with restricted, repetitive behaviors and interests, and sensory differences that sit closer to the core of the condition. ADHD is centered on executive function and attention regulation. Telling them apart, especially when both are present, usually takes a full evaluation from a psychologist or developmental pediatrician.

Can autism be diagnosed in adults?

Yes, and it's increasingly common, especially among women and people who masked their traits growing up. The criteria are the same as for children, though evaluators need to confirm that signs were present in childhood even if nobody caught them at the time. Adults pursue diagnosis for different reasons: to make sense of their own lifelong experiences, to access accommodations, or to better support a child of their own going through evaluation. The ADOS-2 includes a module for adults without intellectual disability, and neuropsychologists with autism expertise can carry out adult evaluations.

What communication supports work best for nonspeaking autistic children?

AAC (augmentative and alternative communication) has the strongest evidence behind it, covering everything from high-tech speech-generating devices and tablet apps to picture exchange systems and low-tech symbol boards. ASHA's position is that AAC should start early and shouldn't be held back out of worry that it'll reduce a child's motivation to speak: research doesn't support that worry, and plenty of kids who use AAC go on to develop speech anyway. The real goal is functional communication, by whatever method works for that child.

Is early intervention really that important?

Research consistently links earlier access to appropriate support with better outcomes in communication, adaptive behavior, and quality of life. The brain's neuroplasticity peaks in the first few years, which is why intervention in that window tends to have a bigger effect. Under IDEA, children from birth to age 3 can get free early intervention services without needing a formal diagnosis first. Nearly every major professional body gives the same practical advice: don't wait for a diagnosis to start getting support.

Sources

1. CDC, Autism Spectrum Disorder Data and Statistics: 1 in 36 children aged 8 years identified with ASD in 2020 ADDM data; prevalence higher in boys; median age of diagnosis approximately 49 months; 38% of autistic children also have intellectual disability
2. American Psychiatric Association, DSM-5 Diagnostic Criteria for Autism Spectrum Disorder: DSM-5 requires persistent deficits in social communication AND at least two of four restricted/repetitive behavior types; severity levels 1-3 reflect support needs
3. Jones W & Klin A, Nature (2013), Attention to eyes is present but in decline in 2-6-month-old infants later diagnosed with autism: Eye-tracking research shows social attention differences in infants later diagnosed with autism can be detected as early as 2 to 6 months
4. Lord C et al., Nature Reviews Disease Primers (2020), Autism spectrum disorder: Autism diagnosis is behavioral; ADOS-2 and ADI-R are research gold standard tools; accurate diagnosis is reliably possible from age 2 in most children
5. ASHA, Autism Spectrum Disorder Practice Portal: SLPs are essential members of autism assessment and treatment teams; AAC should never be withheld waiting for speech; ASHA opposes facilitated communication
6. U.S. Department of Education, IDEA Individuals with Disabilities Education Act: Under IDEA Part C, children birth to age 3 are entitled to free evaluation and services for developmental delays regardless of diagnosis; Part B covers ages 3 and older through school districts
7. Dawson G et al., Pediatrics (2010), Randomized controlled trial of an intervention for toddlers with autism: the Early Start Denver Model: ESDM studied in children aged 18 to 30 months shows effects on language development and adaptive behavior compared to community treatment
8. American Academy of Pediatrics, Autism Identification, Evaluation, and Management: AAP recommends autism-specific screening at 18 and 24 months using M-CHAT-R/F at well-child visits
9. Lai MC et al., Lancet (2017), Prevalence of autism and the female protective effect: Autistic females are more likely to camouflage social difficulties; true male-to-female ratio may be closer to 2:1 than the 4:1 observed in diagnosed populations
10. Journal of Autism and Developmental Disorders, review of sensory processing in autism: An estimated 70 to 96% of autistic individuals show atypical sensory processing, with estimates varying by measurement method and population
11. CDC, Learn the Signs. Act Early. Developmental Milestones: CDC lists specific early signs of autism by age including not responding to name by 9 months, no pointing by 12 months, and regression in skills as red flags
12. Maenner MJ et al., MMWR Surveillance Summaries (2023), Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years, ADDM Network, 2020: 2023 ADDM report using 2020 data found ASD prevalence of 1 in 36 children aged 8; racial disparities in diagnosis persist; prevalence 3.8 times higher in boys than girls