Signs of autism can appear as early as six months of age and vary widely from child to child. Parents and caregivers should watch for missed developmental milestones — like limited eye contact, little babbling, and no response to their name — as well as behaviors such as repetitive movements, echolalia, sensory sensitivities, and resistance to routine changes. Not every autistic child will show every sign, which is why professional screening matters. The American Academy of Pediatrics recommends autism screening at 18 and 24 months. Early diagnosis and intervention can lead to meaningful improvements in communication, learning, and social skills.
Noticing something different about your child’s development can bring up a lot of emotions — concern, confusion, and sometimes uncertainty about what to do next. The good news is that learning about the early signs of autism spectrum disorder (ASD) puts you in the best possible position to help your child thrive.
Autism looks different for every person. Not every autistic child will show every sign, and some children may show only a few. That’s exactly why professional evaluation matters so much. This article walks you through the key signs by age, behaviors that may appear at any stage, and the practical steps you can take if you have concerns.
Signs of Autism in Babies
The earliest signs of autism can appear within the first several months of life. These signs are often subtle, and they show up in the way babies interact — or don’t interact — with the people around them.
By 6 Months
Most babies light up when they see a familiar face. They smile back when you smile at them and show wide-eyed curiosity about the world. If your baby shows few or no big smiles or other warm, joyful expressions by 6 months, that’s worth paying attention to. Limited or no eye contact at this stage is also a potential early sign.
These aren’t automatic cause for alarm on their own. But if they persist or combine with other signs, they may point to a need for further screening.
By 9 Months
Back-and-forth interaction is a cornerstone of early development. By 9 months, most babies are engaged in little “conversations” — sharing sounds, smiling in response, and mirroring facial expressions. Little or no back-and-forth sharing of sounds, smiles, or facial expressions by 9 months can be an early indicator worth discussing with your pediatrician.
Signs of Autism in Toddlers
As children grow, new developmental milestones emerge around language, communication, and social engagement. Missing several of these markers — particularly across multiple categories — is when professionals take a closer look.
By 12 Months
By their first birthday, most toddlers are babbling, pointing at things they find interesting, and turning their head when someone calls their name. Signs that may indicate ASD at this stage include:
- Little or no babbling
- Little or no back-and-forth gestures such as pointing, showing, reaching, or waving
- Little or no response to their name being called
These are some of the most consistent early markers clinicians look for. Missing all three, or even two of them, is a strong signal to seek a developmental evaluation.
By 16 Months
Language development moves quickly in the second year of life. By 16 months, most children have started saying their first words — simple ones like “mama,” “dada,” “ball,” or “more.” If your toddler has very few or no words at this stage, it may be time to talk to your doctor.
Keep in mind that bilingual children or children with other developmental differences sometimes develop language on a slightly different timeline. But if words are absent or nearly absent at 16 months, a professional opinion is always the right next step.
By 24 Months
By age 2, most children are beginning to put two words together — things like “more milk,” “daddy go,” or “big dog.” These aren’t just imitations; they reflect the child combining words to communicate meaning. Very few or no meaningful two-word phrases (not counting imitation or repetition) by 24 months is a key developmental red flag.
Signs of Autism That Can Appear at Any Age
Some signs of autism aren’t tied to a specific age window. They can show up at any stage of childhood — and in some cases, they may become more visible as a child gets older and social expectations increase.
Loss of Previously Developed Skills
One pattern that sometimes appears in autism is regression — when a child loses skills they had already developed. A toddler who was babbling and then stops, or a child who had a few words and then goes quiet, should be evaluated promptly. This kind of skill loss, especially around 18 to 24 months, is taken seriously by developmental specialists.
Social and Communication Challenges
Autistic children often experience the world differently when it comes to connecting with other people. Common signs include:
- Avoiding eye contact, even with familiar people
- Persistent preference for being alone rather than engaging with others
- Difficulty understanding other people’s feelings or expressions
- Delayed language development that doesn’t improve over time
These aren’t signs that a child doesn’t want to connect — many autistic children genuinely want relationships. They may simply communicate and engage in ways that look different from what’s typically expected.
Echolalia and Repetitive Language
Echolalia — the persistent repetition of words or phrases — is something many autistic children do. A child might repeat lines from a favorite cartoon, echo back exactly what someone says to them, or repeat a phrase over and over without using it to communicate. This isn’t misbehavior. It’s often the child’s way of processing language, and it can be a useful starting point for speech therapy.
Repetitive Behaviors and Movements
Repetitive physical behaviors are one of the hallmarks of autism. You might see your child:
- Flapping their hands when excited or overwhelmed
- Rocking back and forth
- Spinning objects or themselves
- Lining up toys or arranging objects in very specific ways
These movements — sometimes called “stimming” — often serve a self-regulating function for autistic children. They help manage sensory input, emotions, or stress. Rather than being random, they often have clear patterns and purposes.
Restricted Interests
Many autistic children develop very focused, intense interests in specific topics — dinosaurs, trains, a particular cartoon character, or weather patterns. While plenty of children have favorite subjects, autistic children may be intensely absorbed in one or two topics to the exclusion of most other things. This depth of interest can be a real strength, though it can also limit flexibility in play and conversation.
Resistance to Routine Changes
Predictability matters deeply to many autistic individuals. Small changes — a different route to school, a new brand of cereal, or a rearranged piece of furniture — can cause significant distress. If your child shows intense, persistent resistance to minor changes in routine or surroundings, this is worth noting.
Sensory Sensitivities
Autistic children often experience sensory input more intensely than others — or sometimes less intensely. You might notice:
- Covering ears at sounds that don’t seem loud to others
- Strong aversion to certain textures in food or clothing
- Unusual sensitivity to lights, smells, or tastes
- Seeking out intense sensory input, like crashing into things or touching everything
These unusual and intense reactions to sensory experiences are not stubbornness or misbehavior — they reflect how the nervous system is processing the world.
When Is Autism Diagnosed?
Autism isn’t always identified at the same time for every child. Some children show clear signs within their first year. Others don’t show noticeable differences until 24 months or later. Some children develop normally up to 18–24 months, and then stop gaining new skills — or start losing the ones they had.
Research shows that by age 2, a reliable autism diagnosis can be made by an experienced professional. Early diagnosis matters because early support makes a real difference in outcomes.
The American Academy of Pediatrics (AAP) recommends that all children be screened for autism at 18 and 24 months, on top of general developmental screenings at 9, 18, and 30 months. If you’re not sure whether your child has been screened, it’s completely appropriate to ask your pediatrician directly.
Practical Next Steps for Caregivers
If anything in this article resonated with what you’ve been observing in your child, here’s what you can do right now.
1. Track Developmental Milestones
The CDC’s Act Early program offers free, easy-to-use milestone checklists for children starting at 2 months of age — available in English and Spanish. Their Milestone Tracker App lets you log observations and share them directly with your child’s doctor. Keeping a record is useful, because it helps clinicians see patterns over time rather than relying on a single appointment.
2. Complete a Screening Questionnaire
The M-CHAT-R™ (Modified Checklist for Autism in Toddlers, Revised) is a short, research-backed questionnaire designed for parents. It takes only a few minutes to complete and helps determine whether a professional evaluation is warranted. If results suggest a higher probability for autism, your next step is a conversation with your pediatrician.
3. Talk to Your Child’s Pediatrician
Don’t wait for your next scheduled visit if you’re concerned. Bring up your observations at your earliest opportunity. Be specific — describe what you’ve seen and when. Pediatricians can refer you to developmental specialists, speech therapists, or early intervention programs. Many parents feel better once the conversation has started, even if there are no clear answers yet.
4. Seek a Professional Evaluation
A pediatrician’s initial screening is just the beginning. A formal developmental evaluation — typically conducted by a developmental pediatrician, child psychologist, or multidisciplinary team — provides a comprehensive picture. This is where an actual diagnosis can be made.
If you’re unsure where to start, the Autism Speaks Resource Guide can help you locate providers and services in your area.
The Value of Acting Early
Early intervention doesn’t mean something is wrong with your child. It means you’re giving them access to support, tools, and therapies at the age when they can make the most difference. Studies consistently show that early behavioral, communication, and developmental interventions lead to meaningful improvements — sometimes dramatically so.
You know your child better than anyone. If something feels off, trust that instinct and take the next step. Getting answers — even if the process takes time — is always better than waiting and wondering.
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