Autism Signs Appearing After 18 Months
The short answer
While some children show signs of autism from early infancy, others develop typically until 12 to 24 months before differences emerge. This can involve regression (losing skills) or plateau (skills stop progressing while peers advance). Late-appearing signs are valid and important to recognize. If you notice changes in your child's development after 18 months, request evaluation.
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By Age
What to expect by age
Development may appear completely typical. The child makes eye contact, babbles, and engages socially. Some subtle differences may only be recognized in retrospect after a later diagnosis.
Some children begin to show differences in this period. Language development may slow, social engagement may decrease, or the child may not add expected milestones like pointing and showing.
This is the most common window for autism signs to become apparent to parents. Changes may include fewer words or lost words, decreased eye contact, less interest in others, new repetitive behaviors, or failure to develop pretend play.
Differences become more obvious as social demands increase. The gap between the child and typically developing peers widens. Evaluation is recommended even if the child had a period of typical development.
Some higher-functioning children are not identified until school demands increase. Late identification does not mean milder autism; it may mean the signs were more subtle or were attributed to other factors.
What Should You Do?
When to take action
- Your child is developing new skills steadily even if at a slightly slower pace
- Your child temporarily regresses during illness or stress but bounces back
- Your child has a brief plateau in one area but is progressing in others
- Your child has stopped adding new words or skills for several months
- Your child seems less socially engaged than they were a few months ago
- You notice new repetitive behaviors appearing alongside slowed development
- Your child has clearly lost previously acquired skills like words, social smiling, or gestures
- Your child's development has regressed significantly in multiple areas
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
Worrying about your baby means you care. That is a good thing.
Related Behavior Concerns
Autistic Regression - Losing Skills
Approximately 25 to 30% of children later diagnosed with autism experience a regression, losing previously acquired skills between 15 and 24 months. This most commonly affects language and social skills. Any loss of skills at any age requires prompt medical evaluation. While regression can occur in autism, it can also indicate other medical conditions that need to be ruled out.
Worried About Autism - When and How to Screen
The AAP recommends autism screening at 18 and 24 months for all children, using the M-CHAT-R/F questionnaire. If you have concerns before these ages, you can request screening earlier. Early signs of autism may include limited eye contact, no pointing by 12 months, no words by 16 months, no pretend play by 18 months, or loss of any previously acquired skills. Trust your instincts as a parent and raise concerns with your pediatrician.
My Baby Is Losing Words or Skills
If your child was consistently using words and has truly stopped, this is something to act on promptly. Regression - the genuine loss of skills a child previously had - is different from a normal plateau or a toddler being too busy to talk, and it always warrants a conversation with your pediatrician sooner rather than later.
Aggressive Play vs Normal Play
Rough-and-tumble play — wrestling, chasing, play-fighting, and superhero battles — is a normal and important part of child development, particularly for toddlers and preschoolers. It helps children develop physical coordination, social skills, self-regulation, and an understanding of boundaries. The key distinction between normal rough play and concerning aggression is whether both children are having fun, there is turn-taking in roles, and no one is intentionally trying to hurt the other.
My Toddler Is Aggressive Toward Pets
Toddlers being rough with pets is extremely common and almost never reflects true aggression or cruelty. Young children lack the motor control to be consistently gentle and do not yet understand that animals feel pain the way they do. With patient, consistent teaching about gentle touch and close supervision, most toddlers learn to interact safely with pets by age 3-4.
My Baby Doesn't Seem Attached to Anyone
By 7-9 months, most babies show clear preferences for their primary caregivers and some wariness of unfamiliar people. If your baby seems equally comfortable with everyone and shows no distress when separated from caregivers, it may simply reflect an easy-going temperament. However, if combined with other social differences, it can occasionally warrant further discussion with your pediatrician.