Autism, or autism spectrum disorder (ASD), can be accurately diagnosed when a child is between 18 and 24 months. Signs of autism often appear much younger, however. Parents might notice signs of autism in babies as young as 6 months old.

Autism is a complex neurological developmental disorder that can range in severity from mild to severe, causing significant disability. For this reason, symptoms can vary greatly.

Developmental delays in babies can sometimes be a sign of ASD. However, babies who are developmentally delayed can also “catch up” to their peers by age 2. While parents can recognize warning signs that point to autism, the disorder is not typically officially diagnosed until a child is at least 18 months. Most often, a diagnosis comes closer to 2 years of age.

Parents are the best advocate for their children. By keeping a close eye on potential ASD warning signs, they can ensure their child is diagnosed earlier and receives more expedient treatment. 

Recognizing Autism in Babies

Research indicates that the earlier autism can be diagnosed, the better the long-term outcome for the child. Early interventions and treatments show greater success.

Parents are in the best position to notice possible early signs of autism since they spent the most time with their child. Daycare providers and preschool teachers also tend to notice these signs early in a child’s life. It is important to realize that there are individual differences in how children develop, so parents should not be focused on just one area of development. Rather, parents should consider more global levels of child development as a sign of autism or other disorders.

Early warning signs for autism can be broken down by age.

6 months old

  • No or little eye contact

  • Lack of smiling

  • Limited facial expression changes

12 months old

  • No babbling

  • Lack of response to name

  • No pointing, waving, or engaging with others in back-and-forth exchanges

18 months old

  • Prefers to play alone

  • Not many words or an inability to string together at least two words

  • Avoiding eye contact

  • Distressed by change and altered routine

  • Repetitive movements like arm flapping

  • Lining up toys

  • Obsession with a particular toy or object

  • Extreme reaction to sensory stimulation, such as sounds, smells, texture, lights, and tastes

  • Repetitive speech patterns

Additional early signs of autism can include regression of language or motor skills that were already learned. Motor skill regression involves losing certain skills that were previously acquired, such as feeding oneself, using the toilet, or putting a shirt on. 

About a quarter of children with autism show a deterioration in language skills. A toddler who had previously been able to use three words for at least a month may no longer speak at all. Babies attempt to communicate with their parents through noises, cries, and gestures. If these communication attempts stop or decline, it could be an early sign of autism.

Social skills can also regress. For example, a toddler may no longer maintain eye contact or engage in play with others. These behaviors ceasing over time could be cause for concern.

What Is the Earliest Age That Autism Signs Can Appear?

Developmental delays and some of the early signs of autism, including lack of eye contact and response to parents, can be noticed as early as 6 months old. All babies and children develop at somewhat different rates, but there are general guidelines for how they progress.

The Centers for Disease Control and Prevention features an online resource of developmental milestones to help parents understand what babies should be doing by what age. While there is always some variability in development timelines, this resource gives an approximate timeline parents can reference. Delays can indicate a possible developmental disorder, including autism.

ASD can present quite a range of signs and symptoms. While some children may only present with slight delays, others may have significant developmental and language delays by 18 months old.

Some older children with autism can cope well enough to mask the symptoms of the disorder until they enter school. At that point, the social pressures often become overwhelming and signs begin to appear. 

What to Do When Autism Is Suspected

If you suspect a developmental delay or autism in your child, talk to your child’s pediatrician.

Doctors will screen for autism between 18 and 24 months, but warning signs can be discussed and recognized sooner than that. Some behavioral signs are often noticeable by parents between 6 and 12 months.

Specific risk factors should also be considered since they can increase the odds for a child to struggle with autism. Risk factors include:

  • Family history of ASD.
  • Certain genetic conditions, such as Down syndrome.
  • Advanced parental age at birth.
  • Extremely low birthweight.

Around 1 out of every 54 children struggles with autism spectrum disorder, the CDC reports. Across the board, early treatment services significantly boost long-term results for children with autism.

Even though autism can be diagnosed prior to age 2, the average age of diagnosis in the United States is still over 3 years old. Because early intervention is so important, parents must advocate for their children when autism is suspected and work with specialists for additional screening to confirm a diagnosis.

Autism Screening Tools

Once a parent brings the possible ASD signs to the attention of a pediatrician, the next step is a more in-depth screening. The M-CHAT -R/F (Modified Checklist for Autism in Toddlers Revised with Follow-Up) is a diagnostic tool that is used to determine the presence of ASD in toddlers as young as 16 months.

After a positive screening for autism spectrum disorder, the child’s pediatrician will generally refer parents to a team of health care professionals that can include a developmental pediatrician, a child psychologist or psychiatrist, speech and language pathologist, and/or a neuropsychologist for a more in-depth evaluation. These steps are generally not performed before the age of 18 months.

Can Autism Symptoms Dissipate With Age?

Since early signs of autism are often behavioral and language delays, it is difficult to make a definite diagnosis much before 18 months or even 2 years of age.

For many children, symptoms do not even present until they are between the ages of 2 and 3. What can appear to be early signs of autism in babies can often fade in the first few years of life.

For example, babies who appear to be behind in language skills and behaviorally can often catch up with their peers by the time they turn 2. Children all develop at somewhat different rates, so they might not fit perfectly into the developmental timeline.

Because of this, some medical professionals hesitate to definitively diagnose autism prior to age 2. Most doctors wait for these symptoms to be considered more stable before making an official diagnosis. Per the CDC, an autism diagnosis can be considered reliable by age 2.

Significant delays and disability related to ASD are less likely to decline in a few years. As a result, doctors consider the severity of the symptoms when making a diagnosis.

All suspected autism symptoms should be monitored closely, even if they seem minor.

The Importance of Early Intervention

The earlier autism is diagnosed, the sooner educational and behavioral interventions can start and the more likely the child is to develop coping and management skills for handling the disorder more successfully.

Without question, early intervention and treatment improve overall quality of life and help children to function better. They can even help to reduce and minimize specific symptoms of autism spectrum disorder, the American Psychological Association (APA) publishes.

While there is no cure for autism, symptoms can be managed effectively with the right treatment. Autism won’t be officially diagnosed in a baby, but if you notice early warning signs, talk to your pediatrician, regardless of your child’s age.

You will continue to monitor these signs as your child grows, and you may get an official diagnosis when your child is closer to 2 years old. Your early observations can mean an early diagnosis, helping your child to get vital treatment services sooner.