Autism Spectrum Disorder (ASD) Symptoms

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On June 6, 2025

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

The signs and symptoms may vary in young children, older children, and adults, but some tend to 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
Having intense focus or intensity related to a specific activity or interest
Having perseverative symptoms (persistent repetition of thoughts, speech patterns, or behaviors beyond what’s considered socially appropriate)
Making the same movements or gestures over and over again, 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)

ASD Symptoms in Babies and Young Children

Symptoms 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.

Children with ASD might display very specific, sometimes intense, interests in subjects that others might not, says Jeremy Veenstra-VanderWeele, MD, director of the division of child and adolescent psychiatry at NewYork-Presbyterian Hospital in New York City. In a conversation, a child with autism might return intently to one topic over and over. That was the case for one child whom Dr. Veenstra-VanderWeele worked with who had a very strong interest in sharks and did not talk about any other topic, for example.

Repetitive behaviors or following the same patterns over and over can also be indicative of ASD 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 have autism include the following:

Delayed skills with language
Doesn’t make eye contact with others
Doesn’t respond to their name by 9 months old
Not showing 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 children with ASD 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 on 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.

According to the most recent version of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), this specific pattern of regression is considered part of the autism spectrum.

ASD Symptoms in Older Children and Adults

Although ASD is a developmental condition that 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 ASD 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 doctor may assess an adult differently than a child. For instance, they may ask about symptoms they have now, what they experienced as a child, and whether they have other health conditions.

Potential symptoms of ASD in older children and adults may include the following:

Finding it hard to understand what others are thinking or feeling
Taking things very literally and struggling to understand sarcasm, idioms, or figures of speech
Difficulty reading nonverbal cues like body language, facial expressions, or tone of voice
Finding it hard to express their own emotions or understand social rules intuitively
Avoiding eye contact or finding it uncomfortable
Having highly focused and intense interests in specific subjects or hobbies
Repeating certain movements, sounds, or phrases
Being more or less sensitive to sensory experiences, such as bright lights, loud noises, and certain textures or smells