Developmental Milestones
Autism spectrum disorder (ASD) is caused by developmental differences in the brain. In some children, the first indications of ASD may appear before the age of 12 months. In other children, symptoms may not be apparent until 24 months or later. These children may meet developmental milestones, and then they stop gaining new skills at around 18 to 24 months, or they lose the skills they once had.
As the brain develops, individual nerve cells migrate from different starting locations to new destinations where they form connections. The brain's structure is very flexible at this stage in an individual's life, and nerve cells that had formed connections in one area may join a migration to a new area thus severing their old connections. The loss of skills observed in some children with ASD is likely due to this migration of nerve cells. See the Learning section of our "Symptoms and Traits" page for more info.
Diagnosing ASD involves reviewing a child's progress through typical developmental milestones as well as the presence of certain restrictive or repetitive behaviors. However, ASD is a spectrum and not all individuals with ASD display the same combination or severity of symptoms.
As the brain develops, individual nerve cells migrate from different starting locations to new destinations where they form connections. The brain's structure is very flexible at this stage in an individual's life, and nerve cells that had formed connections in one area may join a migration to a new area thus severing their old connections. The loss of skills observed in some children with ASD is likely due to this migration of nerve cells. See the Learning section of our "Symptoms and Traits" page for more info.
Diagnosing ASD involves reviewing a child's progress through typical developmental milestones as well as the presence of certain restrictive or repetitive behaviors. However, ASD is a spectrum and not all individuals with ASD display the same combination or severity of symptoms.
Missed Milestones
The following are milestones that may be missed, delayed, or lost by children with ASD. List adapted from the CDC.
- Responding to name by 9 months of age
- Showing facial expressions like happy, sad, angry, and surprised by 9 months of age
- Playing simple interactive games like pat-a-cake by 12 months of age
- Using multiple gestures (e.g., wave goodbye) by 12 months of age
- Sharing interests with others (e.g., shows you an object that he or she likes) by 15 months of age
- Pointing or looking at what others point to by 18 months of age
- Responding when others are hurt or sad by 24 months of age
- Pretending while playing (e.g., does not pretend to “feed” a doll) by 30 months of age
- Understanding other’s feelings or talking about own feelings at 36 months of age or older
- Playing games with turn taking by 60 months of age
- Progression of speech and listening skills (see this general outline by Yale School of Medicine)
- Showing interest in peers
- Making eye contact
- Playing with others
Restricted or Repetitive Behaviors
Other conditions may also cause the same differences in communication and social interaction as ASD, so diagnosing ASD also involves checking for any of the following restricted or repetitive behaviors.
- Lines up toys or other objects and gets upset when order is changed
- Repeats words or phrases over and over (i.e., echolalia)
- Give unrelated answers to questions
- Plays with toys the same way every time
- Is focused on parts of objects (e.g., wheels)
- Gets upset by minor changes
- Is not receptive to the comfort offered by others during distress
- Has obsessive interests
- Must follow certain routines
- Flaps hands, rocks body, or spins self in circles
- Has unusual reactions to the way things sound, smell, taste, look, or feel
- Avoids or resists physical contact
- Only interacts to achieve a desired goal
- Does not adjust to personal space boundaries
- Has flat or inappropriate facial expressions
- Talks in a flat, robot-like, or sing-song voice
- Does not understand jokes, sarcasm, or friendly teasing
Screening
Early identification of ASD can lead to better outcomes. The CDC's Learn the Signs - Act Early program offers free materials including a Milestone Tracker app. These educational materials and tools are designed to help parents and healthcare providers partner in ongoing conversations about a child's development and identify when more specific screening may be needed for ASD or many other developmental disorders.