Early Signs of Autism, Types, and Complications

The specific challenges vary depending on the individual and the severity of the disorder. Autism can appear at different ages for some compared with others, but in most people, early signs of autism start to show up by age 5.

These signs may vary in young children, older children, and adults, but can occur at any age.

Avoiding eye contact or preferring to be alone
Struggling to understand others’ feelings or when others are upset
Not speaking or having trouble developing language skills
Repeating words or phrases without knowing how to use them
Getting upset by minor changes in one’s routine or surroundings
Focusing intently on a specific activity or interest
Persistent repetition of thoughts, speech patterns, or behaviors
Making the same movements or gestures repetitively, such as hand flapping or spinning (also known as stimming)
Having unusual or intense reactions to sounds, smells, tastes, textures, lights, or colors (sensory processing issues)

Autism in Babies and Young Children

Signs of autism in babies and toddlers often involve differences or delays in learning, language, communication skills, or behavior. Common early signs include a child making little eye contact or not responding to their name.

Autistic children might display very specific, sometimes intense, interests in subjects that others might not, says Jeremy Veenstra-VanderWeele, MD, the director of child and adolescent psychiatry at the Columbia University Department of Psychiatry in New York City. In a conversation, an autistic child might return intently to a single topic repeatedly. For example, one child Dr. Veenstra-VanderWeele worked with had a very strong interest in sharks and didn’t talk about any other topic.

Repetitive behaviors or following the same patterns over and over can also be indicative of autism when they happen in combination with other symptoms.

“A lot of these kids display ritualistic behaviors. Certain things have to happen the same way each time,” Veenstra-VanderWeele says. “They might only feel comfortable in your car going the same way to school every day, for instance.”

Other signs that could indicate a baby or toddler may be autistic include the following:

Delayed skills with language

Doesn’t make eye contact with others

Doesn’t respond to their name by 9 months old

Doesn’t show facial expressions reflecting happiness or sadness by 9 months old

Doesn’t wave goodbye or make other gestures by age 1

Doesn’t share interests with others, such as showing you an object they like, by 15 months

Doesn’t point to things that interest them by 18 months

Can’t tell when others are upset or hurt by age 2

Doesn’t notice or join other kids in play by age 3

Doesn’t play pretend (such as with superheroes) by age 4

Doesn’t sing, dance, or act by age 5

Not all autistic children exhibit all of these behaviors, and some signs show up at different ages or in different ways. For instance, a rare pattern of regression called childhood disintegrative disorder (CDD), also known as Heller’s syndrome, is sometimes seen and considered a part of the autism spectrum.

Children with CDD have a period of typical development, usually until age 2 to 4, then experience a significant loss of motor, language, social, and other learned skills.

Autism in Older Children and Adults

Potential signs of autism in older children and adults may include the following:

They have trouble understanding what others are thinking or feeling.

They take things very literally and struggle to understand sarcasm, idioms, or figures of speech.

They have difficulty reading nonverbal cues like body language, facial expressions, or tone of voice.

They find it hard to express their own emotions or understand social rules intuitively.

They avoid eye contact or find it uncomfortable.

They are highly focused and have intense interests in specific subjects or hobbies.

They repeat certain movements, sounds, or phrases.

They are more or less sensitive than others to sensory experiences, such as bright lights, loud noises, and certain textures or smells.

Although autism begins in childhood, it’s sometimes misdiagnosed or not diagnosed until adulthood. Many adults grew up during a time when autism was less understood and studied, meaning early signs might have been overlooked. For these individuals, getting an accurate autism diagnosis as an adult can be helpful for understanding and finding appropriate support.

Diagnosing autism in previously undiagnosed adults can be challenging because the condition is so variable and can affect people differently over time, especially as people develop ways to manage or mask (or camouflage) their difficulties, says Veenstra-VanderWeele.

While the core diagnostic criteria for adults are the same as for children, a psychiatrist may assess an adult differently from a child. For instance, they may ask about current behaviors, what they experienced as a child, and whether they have other health conditions.

How Autism Can Differ by Sex

Signs and prevalence of autism may differ between men and boys and women and girls. ASD was 3.4 times as prevalent among 8-year-old boys as girls in 2022.

Differences in how signs appear can contribute to this disparity. For example, research suggests that autistic women and girls may be more likely to mask their symptoms.

Additionally, some studies suggest that when autistic girls and women experience difficulties, like social challenges or sensory processing issues, they are more likely to turn their distress inward. This might mean they’re more likely to develop anxiety, become depressed, or quietly withdraw.

These internalized responses can be harder to spot, since signs of autism are often compared with externalized behaviors, like having a very visible meltdown or becoming disruptive, which can often lead to quicker recognition of autism.