Most autism signs appear before age 2. Here's what to look for at the 18-month and 2-year mark — and what to do next.
Most children with autism show signs before their second birthday. Knowing what to look for — and when — gives families the best chance to act early. Research shows that children who start therapy in the toddler years make greater gains in communication and social skills than those who start later.
This guide covers the most important red flags at 18 months and 2 years, signs that are easy to overlook, and exactly what to do if something feels off.
How Common Is Autism in Young Children?
According to the most recent data from the CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network, 1 in 31 children in the United States is identified with autism spectrum disorder (ASD) — based on 2022 data from 16 monitoring sites published in April 2025. That's up from 1 in 36 just two years earlier. Boys are diagnosed at roughly four times the rate of girls: about 1 in 20 boys compared to 1 in 70 girls. (Source: CDC ADDM Network, MMWR Surveillance Summary, April 2025.)
Despite how common autism is, the average age of diagnosis is still nearly 4 years old — even though most parents notice something is different around their child's second birthday. A 2023 study in Frontiers in Psychiatry found that parents first raised concerns at an average age of 24.8 months, but diagnosis didn't happen until an average of 37.3 months — a gap of more than 10 months when children could have been receiving support. (Source: Frontiers in Psychiatry, "Autistic Clinical Profiles, Age at First Concern, and Diagnosis," 2023.)
Red Flags at 18 Months
By 18 months, most toddlers are pointing at things they want to share, responding to their name, and saying a handful of words. Signs that may indicate a need for evaluation at this age include:
No pointing to share interest. Pointing to show you something — a dog outside, a favorite toy — is a key social milestone. A toddler who doesn't point by 12 to 14 months may need further evaluation.
No single words. Most children say at least one word by 16 months. If your child isn't using any words by 18 months, bring it up with your pediatrician.
Not responding to their name. By 12 months, most children turn or look when you call their name. Inconsistent responses — especially when the child can hear other sounds — are worth noting.
No back-and-forth communication. This includes babbling, smiling back, and making eye contact during play. A toddler who rarely exchanges glances or expressions may be showing an early sign.
No waving, reaching, or other gestures. By 12 months, most children communicate through gesture — waving bye-bye, reaching to be picked up, shaking their head.
Loss of skills. If your child was saying words or babbling and then stopped, this needs immediate attention. Regression — losing skills a child had already developed — is one of the most important red flags, regardless of age. It typically appears between 15 and 24 months.
The American Academy of Pediatrics (AAP) recommends autism-specific screening at every child's 18-month and 24-month well-child visits — for all children, not just those with visible delays. (Source: AAP Surveillance and Screening Policy, aap.org.)
Red Flags at 2 Years
By age 2, children are typically putting two words together, playing alongside other children, and beginning to pretend. Signs to flag at this age include:
No two-word phrases. "More juice," "daddy go," "big dog" — if your child isn't combining two meaningful words by 24 months, this is a key milestone to discuss with your doctor. Repeating words you say doesn't count.
Not noticing when others are upset. A 2-year-old who doesn't react when a caregiver is hurt or crying may be showing a social awareness difference.
No pretend play. Most 2-year-olds begin simple pretend — feeding a stuffed animal, talking on a toy phone. Limited or absent pretend play is a milestone worth discussing.
Repetitive movements or strong need for routines. Hand flapping, spinning objects, lining toys up in a specific way, or significant distress when a routine changes are all patterns that can accompany autism at this age.
Very focused on one specific interest. A child who is intensely focused on one topic or object — to the point where it's hard to engage them with anything else — may be showing an early marker.
No two-step directions. By 24 months, most children can follow a simple two-step direction, like "get your shoes and bring them here."
Signs That Are Easy to Miss
Some autism signs don't look the way most people expect. A child can have autism and still make eye contact, smile, and say a few words. These subtler signs are often not caught until a child is older:
Unusual reactions to sound, touch, or texture. Covering ears at everyday sounds, avoiding certain foods because of texture, or not reacting to pain the way you'd expect can all be sensory differences that often accompany autism.
Playing alone by preference — consistently. All toddlers play independently sometimes, but a child who consistently avoids interacting with other children or familiar adults may need an evaluation.
Echolalia. Repeating what you say or echoing phrases from TV rather than responding naturally is a communication pattern common in young children with autism.
A very rigid need for sameness. Needing the same route, the same seat, the same bedtime sequence — and becoming very upset when anything changes — is a pattern worth noting.
Late-emerging signs. Around 20% to 40% of children later diagnosed with autism appear to develop typically into their second year and then show regression or a slowdown. This is why follow-up screening at 24 months matters even if the 18-month screen was clear. (Source: CDC "Learn the Signs. Act Early." clinical guidance.)
What to Do If You Notice These Signs
Talk to your pediatrician now — don't wait for the next scheduled appointment. Share your specific concerns with examples. Ask for the M-CHAT-R/F, the standard autism screening tool used at 18 and 24 months. It's a 20-question parent questionnaire that takes about five minutes. (Source: M-CHAT-R/F validation, Robins et al., Pediatrics, 2014; Zheng et al., JADD/Sage, 2024.)
Ask for a developmental evaluation if the screen is positive. A screening is not a diagnosis. If results are concerning, ask for a referral to a developmental pediatrician, child psychologist, or autism specialist.
Request early intervention services. Under the Individuals with Disabilities Education Act (IDEA) Part C, all children from birth through age 2 who have a developmental delay or a diagnosed condition are entitled to free early intervention services. You don't need a diagnosis to ask for an evaluation — a concern is enough. Contact your state's Part C program, or ask your pediatrician for a referral. (Source: U.S. Department of Education, IDEA Part C.)
Ask about a diagnostic evaluation. The gold-standard assessment for autism is the ADOS-2 (Autism Diagnostic Observation Schedule). It's a structured play-based session administered by a trained clinician that looks at how a child communicates and interacts. Intercare offers ADOS-2 evaluations for families who are seeking a diagnosis or a second opinion.
Don't wait to see if they grow out of it. A 2022 clinical trial published in JAMA Pediatrics found that starting social communication therapy between 9 and 12 months reduced the rate of autism diagnosis at age 3 from 20.5% to just 6.7%. The earlier support begins, the more of the developmental window families can use. (Source: JAMA Pediatrics, "Effect of Preemptive Intervention on Developmental Outcomes Among Infants Showing Early Signs of Autism," 2022.)
If your child has already received a diagnosis, our guide on what to do after an autism diagnosis walks through next steps for families — from finding a provider to understanding your insurance coverage.
Frequently Asked Questions
What are the first signs of autism in a 1-year-old?
The earliest signs often appear around 12 months: not responding to their name, not babbling, not pointing, and limited eye contact. A child who was reaching these milestones and then stopped is also a red flag. Talk to your pediatrician right away if you have any concerns — early evaluation is always worth pursuing.
Can a toddler show signs of autism and not have it?
Yes. Some signs — like delayed speech or sensory sensitivity — can have other causes. Only a formal evaluation by a qualified professional can determine whether a child has autism. If you're concerned, the right step is to get evaluated, not to wait.
At what age is autism usually diagnosed?
Most children are diagnosed between ages 3 and 5, even though signs are often present before age 2. The AAP recommends autism-specific screening at 18 and 24 months. Children with more subtle signs are often identified later.
What is the M-CHAT-R/F?
The M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up) is a 20-question parent questionnaire used to screen for autism in children 16 to 30 months old. Pediatricians use it at the 18- and 24-month well-child visits. A positive result doesn't mean your child has autism — it means a follow-up evaluation is recommended.
What's the difference between a screening and a diagnosis?
A screening identifies children who may need further evaluation. It does not diagnose autism. A diagnosis requires a comprehensive assessment by a trained specialist, which typically includes the ADOS-2, parent interviews, and a detailed developmental history.
Does my child need a diagnosis to start ABA therapy?
In most cases, yes — insurance typically requires an ASD diagnosis to approve ABA therapy. However, children under age 3 can receive early intervention services under IDEA Part C before a diagnosis, and the evaluation process can move quickly once you start. Contact Intercare to ask about next steps for your family.
