For parents & clinicians
Early Signs of Autism in Toddlers: What the Research Says
The short answerEarly signs of autism in toddlers can include differences in responding to their name, using gestures, sharing attention, and interacting with others, alongside repetitive movements, strong preferences for sameness, or sensory differences. No single behavior establishes a diagnosis. What matters is the overall developmental pattern—and a professional evaluation when concerns arise. [1] [2] [3] [4]
Key takeaways
- Look for patterns, not a single “tell.” Autism involves both social-communication differences and restricted or repetitive patterns of behavior or interests. [2] [4]
- Notice what your child shares, not only what they say. Gestures, back-and-forth interaction, and pointing to share interest matter alongside words. [1]
- Ask about concerns now. The American Academy of Pediatrics recommends autism screening at 18 and 24 months; concerns at other ages also deserve attention. [2] [3]
- Report lost skills promptly. Losing words, gestures, or social skills warrants medical assessment, whether or not autism is the explanation. [2]
- Support does not have to wait for an autism diagnosis. In the United States, families can contact early intervention directly to request an eligibility evaluation. [12]
A toddler can have a room full of toys and still find the spinning wheel of one truck most interesting. Another may have few words but bring you every discovery. A third may speak in phrases yet rarely point something out just to share the moment.
These differences can leave parents wondering: Is this part of my child's personality, a developmental delay, or something worth asking about?
You do not have to decide whether your child is autistic before asking for help. You only need a concern worth discussing.
Both views include the full guide. Clinician view adds screening and referral details.
What clinicians mean by “signs of autism”
Autism is a neurodevelopmental condition: it affects how a person develops, communicates, interacts, and experiences their environment. Children differ substantially in their strengths and support needs. [2] [5]
Clinicians consider two broad areas:
Social communication and interaction. This includes sharing enjoyment, responding to another person, coordinating gestures with words or gaze, and participating in relationships and play. A toddler might reach for a snack but rarely point across the room to show a parent something interesting. That distinction—requesting something versus sharing an experience—can be useful to describe. [1] [4]
Restricted or repetitive behaviors, interests, and sensory experiences. Examples include repetitive movements or speech, repeatedly focusing on parts of toys, considerable distress when routines change, unusually intense interests, or strong reactions to sounds and textures. [1] [4]
The DSM-5-TR framework is not a checklist parents can score at home. Diagnosis considers developmental history, behavior across situations, functional impact, and other possible explanations. A child does not have to display every example in this article, and examples alone do not establish the diagnosis. [4] [5]
Early signs by age: what is worth discussing?
Use this guide to organize observations, not to diagnose your child. The age-specific examples below draw on CDC guidance. Some belong to an earlier milestone age and remain relevant later. Repetitive and sensory behaviors are not assigned a precise onset age here. [1]
By 12 months: gestures and back-and-forth connection
Bring up concerns such as:
- Few or no gestures, such as waving goodbye.
- Little participation in simple interactive games, such as pat-a-cake.
- Not responding to their name consistently; CDC lists lack of response by 9 months as a possible sign.
- Limited sharing of facial expressions or social engagement. [1]
Observe your child across familiar routines rather than repeatedly testing them. Describe what happens during play, meals, and getting dressed. If name response or language is a concern, ask about hearing as well as development; the AAP recommends hearing evaluation for children with language delay or inattention to language. [2]
By 18 months: pointing to share interest
Concerns to discuss include:
- Not pointing to show you something interesting.
- Rarely bringing or showing objects simply to share interest; CDC lists sharing interests by 15 months.
- Continuing to use very few gestures or having difficulty with back-and-forth interaction.
- Repetitive play or strong sensory reactions occurring alongside social-communication concerns. [1]
A helpful example is not “Does my child ever point?” but “Do they point out an airplane because they want me to notice it too?” Joint attention means sharing attention with someone toward an object or event. It can involve gestures, gaze, or sounds; it is more than making eye contact on command. [2]
By 24 months: look beyond the word count
Discuss:
- Ongoing differences in gestures, shared attention, or reciprocal interaction.
- Not noticing when others are hurt or upset, an example CDC lists at this age.
- Repetitive words, movements, or play, especially with a broader pattern of communication differences.
- Considerable difficulty with changes or sensory experiences that interfere with daily activities. [1]
A vocabulary list cannot answer the autism question by itself. Clinicians consider how children use communication to connect, what they understand, and how their language fits their overall development. [2] [4]
Speech delay vs. autism: understanding the differences
Between 2 and 3 years: social play and everyday flexibility
As social expectations grow, differences may become easier to notice. By 3 years, CDC lists not noticing other children and joining them in play as a possible sign. Persistent differences in sharing enjoyment, interacting, routines, repetitive behavior, or sensory responses also remain relevant. [1] [4]
This does not mean every 2-year-old should already play cooperatively or every child who enjoys playing alone is autistic. Note the age, context, and pattern, and ask a clinician to interpret it. [1] [2] [3] [4]
2-year-old milestones: a practical guide for parents
What does not necessarily mean autism?
Many behaviors on an autism signs list also occur in children who are not autistic. CDC explicitly cautions against interpreting an example in isolation. [1]
Late talking alone. Language delay deserves assessment, but it does not establish autism. Clinicians also examine understanding, gestures, social interaction, hearing, and the broader developmental picture. [2] [4]
Lining up toys alone. Arranging objects is not diagnostic. Describe whether play is varied, whether changes cause distress, and whether there are other developmental concerns. [1] [4]
Eye contact—or its absence. Eye contact is one part of nonverbal communication, not a stand-alone test. Making eye contact does not rule autism out, and reduced eye contact alone does not establish it. [4]
A single difficult day. A diagnostic evaluation considers persistent patterns and developmental history, not one unfamiliar appointment or one frustrating afternoon. [4]
The reverse also matters: a reassuring skill does not cancel out a genuine concern. You can tell your pediatrician both what your child does well and what feels difficult.
Can early signs look different in girls?
Yes—but there is no separate, validated “girls' toddler checklist” offered here. The same developmental concerns deserve attention regardless of sex or gender. [2] [6]
A systematic review and meta-analysis by Loomes and colleagues found evidence that girls meeting autism criteria were disproportionately likely to go undiagnosed. Studies using active population screening found a lower male-to-female ratio than studies relying on existing diagnoses. That supports concern about underrecognition; it does not tell us how any individual girl will present. [6]
The AAP report also discusses how less overt symptoms and fewer externalizing behaviors may contribute to underdiagnosis in girls. Avoid dismissing concerns simply because a child does not match a familiar stereotype. [2]
At an appointment, concrete observations are more useful than trying to prove a “female autism profile”: describe communication, shared attention, play, repetitive behavior, sensory needs, and changes over time.
What if my child loses skills?
Contact your child's healthcare provider promptly if they lose words, gestures, social engagement, or other skills they previously used. Regression needs evaluation; do not assume autism is the explanation. [2]
Development does not always change in a dramatic, overnight way. In a prospective study by Ozonoff and colleagues, researchers repeatedly observed infants who were later diagnosed with autism. They documented declining social-communication behaviors that parents did not always describe as regression. [7]
That finding helps explain why “Did anything change suddenly?” may not capture every developmental concern. It does not mean parents should continuously monitor every smile or blame themselves for missing a subtle change.
Write down what changed, when you noticed it, and which skills were previously consistent. Share that history with the clinician. The aim is to understand the change and identify appropriate care—not to assign fault.
What the research says about early detection
Strongdevelopmental concerns merit assessment
Professional guidance supports ongoing developmental monitoring, standardized screening, and evaluation when concerns arise. CDC states that autism can sometimes be detected at 18 months or younger, and that a diagnosis by an experienced professional can be considered reliable by age 2. Some children will be identified later. [2] [3]
There is still a gap between possible and actual identification. In CDC's 2022 surveillance data, published in 2025, about 1 in 31 children aged 8 years were identified with autism across 16 ADDM Network sites. Among children with a documented autism diagnostic statement in the record-abstraction sites, the median earliest documented diagnosis was 47 months. [13]
Those are community surveillance findings—not a nationally representative toddler sample, not a personal probability, and not proof that every child could have been diagnosed earlier. They do show why responding to developmental concerns matters. [13]
Moderateearly differences can emerge gradually
Ozonoff's prospective study compared infants later diagnosed with autism with a typically developing comparison group. Social gaze, shared smiles, and vocalizations were similar at 6 months, but group differences emerged by 12 months on most measures. [7]
This was a small research sample, not a home screening rule. Its useful lesson is that development unfolds over time: one apparently reassuring early visit cannot answer every later question.
Emerginginfant eye-tracking findings are not a home test
Jones and Klin's landmark Nature study found declining attention to eyes between 2 and 6 months in infants later diagnosed with autism. Researchers measured gaze using specialized eye-tracking methods over time. [8]
This does not mean parents can diagnose autism in a young infant by checking eye contact. Research-level group patterns and an individual diagnostic test are different things. The practical action remains discussing concerns with a healthcare professional.
Why early support matters—and what the evidence cannot promise
Moderatesome early interventions improve specific skills
In Dawson and colleagues' randomized trial, 48 autistic toddlers aged 18–30 months received either the Early Start Denver Model, a developmental-behavioral intervention, or community intervention. After two years, the ESDM group showed greater gains on cognitive and adaptive-behavior measures. [9]
That is evidence of benefit in a specific trial—not evidence that every child needs that program or will have the same outcome. It also does not establish one ideal age or therapy intensity for every family.
A larger, updated systematic review, Project AIM, found benefits for some intervention approaches and outcomes, but also important limitations involving study quality, outcome measurement, and inadequate reporting of potential harms. [10]
The goal is useful, individualized support: communication, participation, everyday skills, comfort, and family priorities—not making a child appear less autistic. Ask providers how goals are chosen, how progress and distress are monitored, and how they adapt to your child's needs. AAP guidance emphasizes shared decision-making with families. [2]
Earlier access can create opportunities to address current needs. It is not a countdown after which improvement becomes impossible, and it is not a reason to blame families navigating waiting lists.
About the evidence labels: These are editorial summaries, not formal GRADE ratings or clinical review. “Strong” indicates established professional guidance for the stated action; “Moderate” indicates supportive research with meaningful limitations; “Emerging” indicates exploratory findings not sufficient for the proposed practical use. They do not rate a child's likelihood of autism.
Screening: what happens at 18 and 24 months?
The AAP recommends autism-specific screening for all children at their 18- and 24-month well visits, alongside ongoing developmental surveillance. A concern at another age should not wait for the next scheduled screen. [2] [3]
One commonly used tool is the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F). It uses caregiver responses and, when indicated, a structured follow-up interview. A positive result means further assessment is warranted—not that the child has been diagnosed. [11]
In its original validation study, 47.5% of children meeting the study's two-stage positive-screen criteria were diagnosed with autism, while 94.6% had a developmental delay or concern. Those findings explain why follow-up matters even when autism is not the eventual diagnosis. They are study-specific results, not a personalized prediction. [11]
A negative screen does not override ongoing concerns. Screening helps guide care; it does not replace developmental history, observation, or clinical judgment. [2] [3] [11]
What to do next: a practical plan
1. Bring specific observations to your pediatrician
You might say: “I'm concerned about how my child shares attention. They reach for what they want but rarely point to show me something. Can we discuss screening and a developmental evaluation?”
Bring brief notes and, if useful, a short video of an ordinary interaction. Include strengths and concerns. Ask whether hearing assessment or speech-language evaluation is appropriate. [2]
2. Contact early intervention in parallel
In the United States, if your child is under 3, contact your state or territory's early intervention program, commonly called IDEA Part C, and request an eligibility evaluation. You can contact the program yourself; CDC states that a doctor's referral is not necessary. Eligibility is based on evaluation and local program rules, not on first obtaining an autism diagnosis. [12]
A cost clarification: Do not assume every therapy is free everywhere. CDC describes these publicly funded programs as providing services free or at reduced cost to eligible children. Ask your local program about eligibility, fees, insurance use, and available financial protections. [12]
For a child 3 or older, contact the local public school system about a preschool special education evaluation—even if your child is not enrolled. Outside the United States, ask your healthcare provider about local developmental services. [12]
How to get early intervention for your child
3. Ask for a developmental or autism evaluation
Ask who can assess your child locally and how to join the referral pathway. A comprehensive assessment may involve a clinician or team with expertise in child development and autism. It considers developmental history, direct observation, strengths, and support needs; no single instrument should determine the diagnosis alone. [3] [4]
4. Leave with a follow-up plan
Ask what support can begin while waiting, when your pediatrician will review progress, and whom to contact if skills change. Request written referral details. You do not need certainty about the diagnosis to keep asking for your child's developmental needs to be addressed. [2] [12]
Clinician view: screening, interpretation, and referral
Additional detail for clinicians; the parent-facing action plan remains relevant in either view.
- Combine surveillance and screening. AAP recommends autism-specific screening at 18 and 24 months. Obtain caregiver concerns and developmental history rather than relying on the screening score alone. [2]
- Use the validated process. In the Robins validation study, the two-stage M-CHAT-R/F criteria were an initial score of at least 3 and follow-up score of at least 2. Follow the instrument's current administration and referral instructions; do not improvise cutoffs or omit indicated follow-up. [11]
- Explain the metrics. The study estimated sensitivity of 85.4% and autism positive predictive value of 47.5% for that two-stage threshold. Sensitivity describes detection among cases identified by the study; PPV describes the proportion of positive screens associated with autism. Neither is a universal guarantee. Not all screen-negative children received diagnostic evaluation, limiting certainty about missed cases. [11]
- Refer on clinical concern. Persistent concerns merit evaluation even after a negative screen. Consider hearing and language assessment, early intervention eligibility, and diagnostic referral in parallel. [2] [11] [12]
- Close the loop. Discuss how families will access referrals and revisit concerns. A screening result without an accessible next step is not the end of the clinical process. [2]
Questions to ask your provider
Frequently asked questions
What are the earliest signs of autism in toddlers?
Possible signs include differences in response to name, gestures, pointing to share interest, and back-and-forth interaction, together with repetitive behavior, strong preferences for sameness, or sensory differences. No single sign establishes autism; concerns deserve professional assessment. [1] [2] [3] [4]
Does speech delay always mean autism?
Can an autistic toddler make eye contact and be affectionate?
At what age can autism be diagnosed?
CDC states that autism can sometimes be detected at 18 months or younger and that a diagnosis by an experienced professional can be considered reliable by age 2. Some children are identified later. [3]
Does a positive M-CHAT-R/F mean my child is autistic?
No. It indicates a need for further assessment. Some children who screen positive have autism, while others have different developmental delays or concerns. Complete any indicated follow-up with your healthcare provider. [11]
Do we need an autism diagnosis before requesting early intervention?
No. In the United States, families of children under 3 can contact their state or territory's early intervention program directly to request an eligibility evaluation. Eligibility and costs depend on the program and the child's evaluated needs. [12]
Should I wait if my toddler loses words or gestures?
Contact your child's healthcare provider promptly. Loss of previously used skills warrants evaluation, whether or not autism is the explanation. [2]
The bottom line
You do not need to turn everyday life into a test. Notice how your child communicates, shares experiences, plays, and responds to their surroundings. If something concerns you, bring it up—and ask for a concrete next step.
An evaluation is not a verdict on your child's future. It is a way to understand their development and find support that fits.
Sources
- Centers for Disease Control and Prevention. Signs and Symptoms of Autism Spectrum Disorder. CDC. ↩
- Hyman SL, Levy SE, Myers SM; Council on Children With Disabilities, Section on Developmental and Behavioral Pediatrics. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics. 2020;145(1):e20193447. DOI: 10.1542/peds.2019-3447 · PubMed · Full text, University of Washington copy. ↩
- Centers for Disease Control and Prevention. Screening for Autism Spectrum Disorder. CDC. ↩
- Centers for Disease Control and Prevention. Clinical Testing and Diagnosis for Autism Spectrum Disorder. CDC. Includes DSM-5 diagnostic criteria; used with the APA's DSM-5-TR-based overview below, not as a claim that the full DSM-5-TR manual was reviewed. ↩
- American Psychiatric Association. What Is Autism Spectrum Disorder? January 2024. APA. Clinical overview citing DSM-5-TR (2022); not the full diagnostic manual. ↩
- Loomes R, Hull L, Mandy WPL. What Is the Male-to-Female Ratio in Autism Spectrum Disorder? A Systematic Review and Meta-Analysis. Journal of the American Academy of Child & Adolescent Psychiatry. 2017;56(6):466–474. DOI: 10.1016/j.jaac.2017.03.013 · PubMed · Accepted manuscript, UCL. ↩
- Ozonoff S, Iosif AM, Baguio F, et al. A Prospective Study of the Emergence of Early Behavioral Signs of Autism. Journal of the American Academy of Child & Adolescent Psychiatry. 2010;49(3):256–266.e1–2. PubMed · Full text. ↩
- Jones W, Klin A. Attention to eyes is present but in decline in 2–6-month-old infants later diagnosed with autism. Nature. 2013;504:427–431. DOI: 10.1038/nature12715 · Publisher · PubMed. ↩
- Dawson G, Rogers S, Munson J, et al. Randomized, controlled trial of an intervention for toddlers with autism: the Early Start Denver Model. Pediatrics. 2010;125(1):e17–e23. DOI: 10.1542/peds.2009-0958 · PubMed · Full text. ↩
- Sandbank M, Bottema-Beutel K, Crowley LaPoint S, et al. Autism intervention meta-analysis of early childhood studies (Project AIM): updated systematic review and secondary analysis. BMJ. 2023;383:e076733. DOI: 10.1136/bmj-2023-076733 · Full text. ↩
- Robins DL, Casagrande K, Barton M, Chen CMA, Dumont-Mathieu T, Fein D. Validation of the modified checklist for Autism in toddlers, revised with follow-up (M-CHAT-R/F). Pediatrics. 2014;133(1):37–45. DOI: 10.1542/peds.2013-1813 · PubMed · Full text. ↩
- Centers for Disease Control and Prevention. Early Intervention. Learn the Signs. Act Early. CDC. ↩
- Shaw KA, Williams S, Patrick ME, et al. Prevalence and Early Identification of Autism Spectrum Disorder Among Children Aged 4 and 8 Years—Autism and Developmental Disabilities Monitoring Network, 16 Sites, United States, 2022. MMWR Surveillance Summaries. 2025;74(2):1–22. DOI: 10.15585/mmwr.ss7402a1 · Full report. ↩
Medical and editorial disclaimer
This article is educational information, not medical advice, a screening instrument, or a diagnosis. Discuss developmental concerns and changes in skills with your child's healthcare provider. Pediatric Research Review summarizes published research and authoritative guidance; we do not conduct the studies described here. This article was prepared by the Pediatric Research Review Editorial Team and has not been clinically or medically reviewed. Sources checked November 5, 2026.
