Autism is a neurodevelopmental disorder that affects how people communicate and interact with the world around them.
It can involve language and communication challenges, issues with social interaction, repetitive behaviors, and difficulty coping with change and altered routines. Autism looks different for everyone, varies by the level of support needed, and often appears in early childhood, though some people aren’t diagnosed until adolescence or adulthood.
Signs and Symptoms of Autism
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.
Types and Severity of Autism
Because autism is a spectrum, signs don’t look the same or cause the same degree of challenges for everyone. Doctors describe the severity of a person’s autism based on how much support they need. This is broken down into three levels: level 1 (requiring support), level 2 (requiring substantial support), and level 3 (requiring very substantial support).
Level 1 (Requiring Support)
People diagnosed with level 1 autism require some support in their day-to-day functioning. While noticeable, their challenges with social communication and flexibility might not be immediately obvious to everyone.
Level 1 autism was previously referred to as high-functioning autism or Asperger’s syndrome; these terms are now part of the singular ASD diagnosis in DSM-5 and DSM-5-TR.
People with level 1 autism often have average or above-average intelligence and don’t have language delays, but they still experience difficulties with social interaction, understanding social cues or expectations, and coping with change. Symptoms of level 1 autism may include the following:
Difficulty starting conversations or making the first move socially
Responding to others’ attempts to connect in ways that seem unusual or don’t lead to a typical back-and-forth
Appearing to have less interest in social activities or engagement with others
Having certain repetitive actions or routines that can get in the way of daily tasks or make it hard to adapt to new things
May have difficulty shifting their attention away from a very strong interest or specific topic they’re focused on
Level 2 (Requiring Substantial Support)
People diagnosed with level 2 autism require substantial support because they have more significant challenges with social and communication skills and behaviors, and these challenges are apparent even when they have support in place. Symptoms of level 2 autism can include the following:
Difficulty with both spoken language and understanding or using nonverbal cues like gestures, facial expressions, or body language
Showing little interest in starting social interactions or finding it very hard to do so
Struggling to build friendships or connect with others, even when support is available
Having very specific, intense interests or engaging in repetitive actions that are obvious to most people and often get in the way of daily activities
Becoming very upset or frustrated if their strong interests, routines, or repetitive behaviors are disrupted
Level 3 (Requiring Very Substantial Support)
People diagnosed with level 3 autism require very substantial support due to severe challenges with social, learning, and communication skills and behaviors that significantly interfere with functioning in all areas of life. Both verbal and nonverbal social communication are severely limited. Symptoms of level 3 autism can include the following:
Making few, if any, attempts to start social interactions with others
Showing minimal, if any, reaction when other people try to engage with them socially
Having extremely limited use of spoken language, perhaps only a few words or no words at all
Being intensely focused on specific topics or objects, following rigid routines, or engaging in repetitive actions that disrupt most areas of life
Finding it incredibly difficult to cope with any changes in their routine or surroundings
Potential Complications of Autism Spectrum Disorder
Autistic people often experience other medical and psychiatric conditions. Commonly associated conditions and challenges include the following:
Intellectual disabilities and differences in language development
Problems in school, including difficulties with learning and academic achievement
Challenges with employment and maintaining a job
Social isolation and challenges in forming and maintaining relationships with peers
Experience of victimization or being bullied in school or elsewhere
When to See a Doctor
If you notice certain signs or have concerns about yourself or your child, it’s important to talk to a doctor for a potential diagnosis. Let your or your child’s doctor know if you or your child has any of the symptoms described here.
The Takeaway
Autism is a complex neurodevelopmental disorder with a broad spectrum, with signs that vary from person to person and can change over time.
Characteristics can show up differently depending on a person’s age and required level of support, and may sometimes present differently in men and boys than in women and girls.
Autism is often associated with other medical, psychiatric, or behavioral health conditions and can lead to challenges in areas like learning, social interaction, and daily living.
If you have concerns about developmental differences or potential signs of autism, talking to a healthcare professional is the best way to get an accurate evaluation and find appropriate support.
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Autism Spectrum Disorder. Mayo Clinic. May 22, 2025.
ICD-10, International Statistical Classification of Diseases and Related Health Statistical Classification of Diseases and Related Health Problems. Tabular List, 2022. Centers for Disease Control and Prevention. March 17, 2022.
How to Pursue an Autism Diagnosis as an Adult. Cleveland Clinic. November 20, 2024.
Shaw KA et al. Prevalence and Early Identification of Autism Spectrum Disorder Among Children Aged 4 and 8 Years — Autism and Developmental Disabilities Monitoring Network, 16 Sites, United States, 2022. Centers for Disease Control and Prevention. April 17, 2025.
Horwitz E et al. Sex Differences in the Course of Autistic and Co-Occurring Psychopathological Symptoms in Adolescents With and Without Autism Spectrum Disorder. Autism. January 21, 2023.
Napolitano A et al. Sex Differences in Autism Spectrum Disorder: Diagnostic, Neurobiological, and Behavioral Features. Frontiers in Psychiatry. May 13, 2022.
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He earned his medical degree from the Wake Forest University School of Medicine and completed his general residency and child and adolescent fellowship with the Palmetto Health Alliance/University of South Carolina School of Medicine.
He has worked in an academic setting, an acute adolescent inpatient unit, an autism clinic, in juvenile justice, with college students, and as a traveling psychiatrist prior to his current positions.
Brian is a New York City–based science and health journalist. Whether interviewing newsmakers — from Buzz Aldrin, Katie Couric, and Dr. Anthony Fauci to Wendy Williams and the cast of Queer Eye — and tech experts about the latest innovations, or leading medical researchers, he's comfortable chatting with just about anyone.
Brian’s work has been published by The Atlantic, The Paris Review, The New York Times For Kids, CBS News, The Today Show, Barron's PENTA, Engadget, Healthline, and more. He's also hosted podcasts: On Topic, Off Script with Brian Mastroianni as well as Re:solve Talks, from Re:solve Global Health.
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