Autism is a neurodevelopmental condition characterized by differences in social communication, social interaction, and the presence of restricted, repetitive patterns of behavior, interests, or activities.
Estimates from 2020 indicate that about 1 in 36 US 8-year-olds had been diagnosed as autistic (Maenner et al., 2023). Most researchers attribute the rise from earlier, much lower estimates mainly to broader diagnostic criteria and greater awareness.
Although autism is often diagnosed in childhood, some people may receive a diagnosis in adulthood.
Autism is present from birth and is lifelong. Autistic individuals may display a range of traits that vary on a spectrum.
Many non-autistic people can relate to some autistic traits. However, a person must meet specific criteria to be officially diagnosed as autistic.
It is essential to recognize that autism is a natural variation in human neurodiversity, and while it may present challenges, it also comes with unique strengths and perspectives.
While the diagnostic criteria uses pathologizing language to describe autism, this article aims to describe the signs in a value-neutral manner, acknowledging that apparent ‘deficits’ are only through the context of the society we live in.
This article uses identity-first language (“autistic person”). A 2026 UK survey of 902 neurodivergent adults found that autistic participants significantly preferred it to person-first phrasing (Pearson et al., 2026). Individual preferences vary, so a person’s own choice comes first.
Below will be a discussion of some of the main signs of autism and examples of how this may look.
Please keep in mind that this is not an exhaustive list and should not be used as a diagnostic tool. Talk to a health professional if you think you may be autistic and want to seek an official diagnosis.
Signs of Autism: Social Communication and Interaction
Autism is identified from behavior, not a biological test. There is no blood test or brain scan for it. The DSM-5 criteria (American Psychiatric Association, 2013) group autistic traits into two domains: social communication and interaction, and restricted, repetitive behaviors.
Older sources describe a “triad of impairments” from Lorna Wing’s work, which listed social interaction, communication, and repetitive behavior separately. DSM-5 merged the first two because they rarely occur apart.
Within the first domain, autistic individuals have differences in 3 areas:
1. Social-emotional reciprocity
Examples:
- Back-and-forth conversation can feel challenging
- Speaking literally and precisely (which can be interpreted as bluntness)
- Dislike for small talk, tendency to overexplain
- Find it hard to share emotions with others
- Struggle with vague language or ‘reading between the lines’
Note: Reciprocity is a two-way street, so a mismatch between autistic and non-autistic communication styles can be misinterpreted (see the double empathy problem). As Milton (2012) explains, it is a "disjuncture in reciprocity between two differently disposed social actors." Both sides struggle to read each other.
2. Nonverbal communication differences
Examples:
- Differences in eye contact (such as avoiding it)
- Differences in facial expressions (either lack of or using expressions not socially typical for the situation)
- Difficulty understanding non-verbal speech
- Misunderstanding social cues
Some nonverbal differences appear very early. Joint attention means sharing focus on an object or event with another person, usually through gesture or eye contact.
Clinicians can screen for these signs at 18 months with the Checklist for Autism in Toddlers (CHAT). Its results suggest that a lack of pretend play and joint attention might be the clearest early indicators of autism (Scott, 2004).
3. Relationship differences
Examples:
- Difficulties making friends or forming relationships
- Difficulty maintaining friendships
- May prefer to be alone
- May want friendships but struggle due to other autistic traits
Note: When non-autistic people are accepting of autistic differences, it can be easier for autistic people to make and maintain friends.
Signs of Autism: Repetitive Behaviors and Sensory Differences
According to the DSM-5, autistic individuals must also experience at least 2 of the 4 types of restricted, repetitive behaviors outlined below:
1. Repetitive movements
Self-stimulating behaviors (also known as stimming) can provide a pleasing sensory experience for autistic individuals. They can also help regulate emotions or cope with an overwhelming situation.
Examples of stimming can include:
- Hand flapping
- Repeating specific words or phrases (echolalia)
- Watching the movement of an object
- Looking at a visually pleasing color or something shiny (e.g., the way someone’s hair shines)
- Listening to a certain sound or song repeatedly
- Smelling (e.g., having a favorite spice to open and smell)
2. Preference for sameness or routines
Examples:
- Preferring a structured day
- Becoming upset if plans change suddenly
- Feeling stressed when things are uncertain and ruminating on distress
- Needing clarity
- Eating the same or similar food every day
- Setting strict rules (e.g., I must study for 2 hours every day, I must go to the gym every 3 days)
Note: Displaying one or more of these behaviors is not indicative of autism on their own.
3. Fixated interests
Examples:
- Having intense special interests (e.g., in history, transportation, books, celebrities, a video game, politics)
- Spend much free time invested in special interests
- Collecting objects or information related to the special interest
- Feeling happy and relaxed when engaging in a special interest
- Feeling sad or frustrated when not engaging in the special interest
- Wanting to speak about special interests to others
4. Sensory differences
Autistic individuals may have hyper or hyposensitivity to sensory input. This can vary from person to person, with some seeking out sensory stimuli while others actively avoiding the same stimuli.
Some examples of sensory differences include:
- Dislike fluorescent lights
- Easily startled by loud noises
- Indifferent to pain
- Disliking hot weather
- Disliking certain food textures
- Disliking tight or scratchy clothes
- Strong aversion to certain smells
Many autistic individuals may have a strong response to certain sensory stimuli and may even report feeling pain or discomfort.
Is masking a sign of autism?
Masking (or camouflaging) is a strategy some individuals use to hide or suppress autistic traits, to fit in with societal norms and avoid stigma.
Masking can be used by any autistic person. It might be caused by societal expectations of what is deemed ‘normal’ or ‘appropriate’ behaviors, or by past bullying or discrimination.
What Masking Looks Like
Masking example: you are meeting a friend for coffee who has just told you she has unfortunately lost her job. While you may genuinely feel bad for her, it does not feel natural to express this.
However, you don't want her to think you don't care. So you adjust your facial expression to one of concern, with a frown and furrowed brows. You tell her you are so sorry this happened.
Other examples of masking autism include:
- Suppressing stimming, especially in public
- Holding back from talking about focused interests
- Pretending to be fine when plans go wrong
- Following a social script to cope with social situations
- Pretending to understand a vague request
The Costs of Masking
Masking is mentally and emotionally exhausting, often leading to burnout and fatigue. Constantly conforming to neurotypical norms and hiding one’s true self can also have detrimental effects on mental health, such as increased anxiety.
In Hull et al.’s (2017) online survey of 92 autistic adults, participants described the toll of masking in their own words.
One wrote, “It’s exhausting! I feel the need to seek solitude so I can ‘be myself’ and not have to think about how I am perceived by others.”
Another described the longer-term cost. “I feel like the weight of a black cloud is hanging on me having to be this fake version of me.”
These are the views of a selected group of participants, not every autistic person.
How Masking Affects Diagnosis
Masking can delay or prevent a diagnosis. Camouflaging is reported more often by autistic women and girls, though it is not limited to them. It can hide difficulties from clinicians using tools developed mainly on male samples.
Loomes et al. (2017) pooled sex ratios from 54 studies. This meta-analysis found an overall male-to-female ratio of 3:1, narrower than the 4:1 often quoted.
It narrowed further in studies that screened whole populations instead of relying on clinic referrals. This suggests many autistic girls are missed rather than absent.
Researchers can now measure masking. The Camouflaging Autistic Traits Questionnaire (CAT-Q) is a self-report scale with subscales for compensation, masking, and assimilation. It was validated in a large sample of autistic and non-autistic adults (Hull et al., 2019).
It is, therefore, important to take into account masking behaviors when addressing the traits of autism, and it should be considered during the diagnostic process.
Autism in adults
There is often a misconception that autism is something that can only impact children. However, autistic children grow up to be autistic adults.
The signs of autism noted above can apply to both children and adults in varying ways.
The challenges associated with autism, such as difficulties in social communication, restricted interests, and sensory sensitivities, continue to impact individuals throughout their lives.
As awareness and understanding of autism have grown, more adults are being diagnosed as autistic, highlighting the importance of recognizing and supporting autistic individuals across the lifespan.
In many cases, autistic adults may have learned compensatory methods to cope with living in a world that is not always neurodiverse-friendly.
Adult diagnosis can be harder.
Many diagnostic tools were developed and validated mainly on male samples (Loomes et al., 2017). Accuracy is also lower for adults and people who mask. Rising demand has created long waiting lists in many health systems.
Likewise, many autistic adults have learned what they do and do not like and have been able to live a life for themselves that is authentic to who they are.
Autism often co-occurs with other conditions, which can complicate assessment.
A UK population-derived study of children found that over 70% of autistic children met criteria for at least one other psychiatric condition (Simonoff et al., 2008). Almost half met criteria for two or more.
The most common were social anxiety, ADHD, oppositional defiant disorder, and specific phobias. Because their traits can resemble and mask one another, anxiety, ADHD, and autism can be hard to tell apart.
Key Takeaways
- Core Signs: Autistic people differ in social communication and interaction, and show restricted, repetitive behaviors, interests, or sensory responses.
- Spectrum: Autistic traits vary widely between people. No single trait on its own indicates autism.
- Early Signs: In toddlers, a lack of pretend play and joint attention might be the clearest early indicators.
- Double Empathy: Misunderstandings between autistic and non-autistic people run both ways, not only from the autistic side.
- Masking: Many autistic people hide their traits to fit in. This is exhausting and can delay diagnosis, especially in women and girls.
- Diagnosis: This list is not a diagnostic tool. A health professional can assess whether the criteria are met.
References
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