About 1 in 31 children in the United States are identified with autism spectrum disorder, so if you’re noticing something different about your child’s development, you’re far from alone in asking this question. Autism shows up as a pattern of differences in social communication and behavior, and the signs can appear as early as the first year of life. No single behavior means your child is autistic, but a cluster of specific signs, especially ones that persist over time, is worth paying attention to.
Early Signs in Babies and Toddlers
Many parents first sense something is off during the first two years, often around everyday interactions that don’t unfold the way they expected. The CDC identifies several age-specific red flags worth watching for:
- By 9 months: Not responding to their name. Not showing facial expressions like happiness, sadness, or surprise.
- By 12 months: Not playing simple interactive games like pat-a-cake. Using few or no gestures, such as waving goodbye.
- By 15 months: Not sharing interests with you, like holding up a toy to show you something they like.
- By 18 months: Not pointing at things to direct your attention to something interesting.
- By 24 months: Not noticing when others are hurt or upset.
A child who avoids eye contact or doesn’t keep it during interactions is another consistent early indicator, and it can show up at any point in these early years. Keep in mind that missing one milestone doesn’t automatically point to autism. What matters is the overall pattern, particularly when several of these signs appear together.
When a Child Loses Skills They Already Had
Some children develop typically at first and then lose ground. This is called regression, and it most often happens between ages 1 and 2. Parents describe their toddler losing words they were already using and pulling back from social engagement, showing less interest in the world around them. Research tracking infants over time found that at 6 months, babies who were later diagnosed with autism looked similar to their peers in gazing at faces, smiling, making eye contact, and vocalizing. By 12 months, those skills had started to decline and continued dropping over the following months.
Regression can be gradual rather than sudden. One child’s parents described how around 18 months, he slowly began losing both social and speech skills. If your child was babbling, saying a few words, or making good eye contact and then stops, that shift is significant regardless of whether it happens overnight or over weeks.
Social Communication Differences
The core of autism involves differences in how a child connects and communicates with other people. This goes beyond speech delays. A child on the spectrum may not engage in the natural back-and-forth of social interaction: they might not respond when you try to start a conversation or a game, or they may talk at length about a topic without picking up on your reactions. They might struggle to read body language and facial expressions, or use very few gestures themselves.
As children get older, these differences show up in friendships. A school-age child might have difficulty adjusting their behavior to different social settings, like being too formal with peers or too casual with adults. They may struggle with imaginative play that involves cooperating with other kids, or they may show little interest in other children altogether. Some children want friends badly but can’t figure out the unwritten rules of social interaction, leading to frustration on both sides.
Repetitive Behaviors and Rigid Routines
The second hallmark of autism is a pattern of repetitive behaviors or unusually intense interests. This can look very different from one child to the next. Some common examples include lining up toys in a specific order, repeating phrases they’ve heard (sometimes from TV shows or conversations), or flipping and spinning objects. Some children develop strict routines and become extremely distressed when those routines change, even in small ways. They may insist on taking the same route to school, eating the same food every day, or greeting people with the same scripted words.
Intense, focused interests are another piece of this pattern. All kids have favorite topics, but in autistic children, these interests are often unusually narrow and consuming. A child might memorize every detail about trains, specific animals, or a particular video game to a degree that feels different from a typical hobby. They may also develop strong attachments to unusual objects.
Sensory Reactions That Stand Out
Many children on the spectrum experience the world through a sensory filter that’s turned up too high, too low, or both. A child who is over-responsive to sensory input may gag on certain food textures, cover their ears at sounds other kids ignore, refuse to wear specific fabrics, or become overwhelmed by bright lights or crowded spaces. On the other end, a child who is under-responsive may seem not to notice pain or temperature changes, or may seek out intense sensory experiences like spinning, crashing into furniture, or excessively touching and smelling objects.
Some children have a mix of both. They might be fascinated by lights and movement (seeking that input) while being deeply bothered by certain sounds (avoiding that input). Sensory differences alone don’t mean autism, but when they appear alongside social communication challenges and repetitive behaviors, they’re an important piece of the picture.
Why Girls Are Often Missed
Autism is frequently underdiagnosed or diagnosed later in girls because it often looks different than it does in boys. Girls tend to be more socially motivated, so they work harder to fit in. They learn to mimic socially acceptable behavior by watching the people around them, copying facial expressions, and studying social cues from TV shows and movies. This “masking” can be effective enough that adults don’t notice anything unusual, but it comes at a real cost: mental exhaustion, stress, and anxiety.
A girl on the spectrum might manage to maintain a friendship or two, participate in conversations, and even force herself to make eye contact despite finding it uncomfortable. Her struggles might look like shyness, which is considered a socially acceptable trait for girls and doesn’t raise the same alarms. If your daughter seems to be working unusually hard at social situations, comes home drained after school, or seems like a different person at home than she is in public, those are patterns worth exploring.
A Screening Tool You Can Use at Home
The M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up) is a free screening questionnaire designed for children between 16 and 30 months. It’s a set of 20 yes-or-no questions that you can complete yourself. The scoring breaks down into three ranges:
- Score of 0 to 2: Low likelihood of autism. The screen is negative.
- Score of 3 to 7: Moderate likelihood. A follow-up on the specific flagged questions is recommended, and if two or more items still come back elevated, a professional evaluation is the next step.
- Score of 8 to 20: High likelihood. The recommendation is to go directly to a professional evaluation without the follow-up step.
This tool is a screening, not a diagnosis. A positive result means your child should be evaluated further, and a negative result doesn’t guarantee autism isn’t present, especially in older children or girls who mask well. Pediatricians typically administer this at the 18- and 24-month well-child visits, but you can also access it online at mchatscreen.com.
What a Professional Evaluation Looks Like
A formal autism diagnosis requires a comprehensive evaluation by a specialist, typically a developmental pediatrician, child psychologist, or child psychiatrist. There’s no blood test or brain scan for autism. The evaluation involves observing your child, reviewing their developmental history, and assessing their behavior against established criteria.
For a diagnosis, a child needs to show persistent difficulties in all three areas of social communication: back-and-forth social interaction, nonverbal communication like gestures and eye contact, and building and maintaining relationships. They also need to show at least two types of repetitive or restricted behavior, whether that’s repetitive movements, rigid routines, intense fixated interests, or unusual sensory responses. These patterns need to be present across different settings, not just at home or just at school.
Wait times for evaluations can be long, sometimes six months or more depending on where you live. If you’re concerned, request a referral now rather than waiting to see if your child “grows out of it.”
Why Acting Early Matters
Early intervention, ideally before preschool age, takes advantage of a period when a young child’s brain is still rapidly forming and more responsive to targeted support. Children who receive help at ages 2 or 3 have a better chance of developing communication, social, and adaptive skills that carry forward. Current guidelines recommend starting intervention as soon as autism is diagnosed or even seriously suspected, rather than waiting for a confirmed diagnosis.
Some children who receive early, intensive support make enough progress that they no longer meet the criteria for an autism diagnosis as they get older. Those children tend to share certain traits: they were diagnosed and treated young, had stronger-than-average language and motor skills for an autistic child, and had higher cognitive ability. But even for children who remain on the spectrum throughout their lives, earlier support consistently leads to better long-term outcomes in communication and daily functioning. The most important thing you can do right now, if you’re seeing the signs described here, is start the process of getting your child evaluated.