ASD stands for autism spectrum disorder, a developmental condition that affects how a person communicates, interacts socially, and experiences the world around them. About 1 in 31 children in the United States (3.2%) are identified with ASD by age 8, and it is over three times more common in boys than girls. The word “spectrum” reflects the wide range of ways autism can show up, from people who need round-the-clock support to those whose differences are subtle enough to go unnoticed for decades.
Core Traits of Autism
A diagnosis of ASD rests on two broad categories of traits. The first involves differences in social communication and interaction. This can look like difficulty with the natural back-and-forth of conversation, limited use of eye contact or gestures, or trouble building and maintaining friendships. Some autistic people struggle to read facial expressions or adjust their behavior for different social settings. Others may not initiate social contact at all, while some simply interact in ways that feel out of step with what others expect.
The second category involves restricted or repetitive patterns of behavior. These include repeating certain movements or phrases, needing routines to stay the same, developing intensely focused interests, or reacting unusually to sensory input like sounds, textures, or lights. A child might line up toys in precise rows, insist on eating the same meal every day, or become deeply distressed by small changes in schedule. An adult might have an encyclopedic knowledge of a narrow topic or find the hum of fluorescent lighting unbearable. To receive a diagnosis, a person needs to show traits in both categories, and those traits need to have been present from early development, even if they weren’t recognized at the time.
Sensory Differences
Roughly 90% of autistic people experience the world through atypical sensory processing. This was considered important enough to be added to the official diagnostic criteria in 2013. Sensory differences fall into two main patterns: hyper-reactivity (over-responsiveness) and hypo-reactivity (under-responsiveness), and many people experience both, depending on the sense involved.
Hyper-reactivity means certain sensory input feels overwhelming. A clothing tag might feel like sandpaper, a crowded restaurant might be painfully loud, or certain food textures might trigger a gag reflex. People who are hyper-reactive often avoid the triggering input or become distressed when they can’t escape it. Hypo-reactivity is the opposite: a reduced response to sensation. Someone might not notice pain, seem indifferent to temperature changes, or seek out intense sensory experiences like spinning, pressing against hard surfaces, or smelling objects. Touch is one of the most commonly affected senses, but sensory differences can involve any combination of sight, sound, smell, taste, and body awareness.
Support Levels
Rather than the old categories of “mild” or “severe” autism, clinicians now assign one of three support levels. Each level is rated separately for social communication and for repetitive behaviors, so a person might need more support in one area than the other.
- Level 1 (requiring support): The person can generally function independently but has noticeable difficulty with social interactions, organization, or flexibility. Without support, these challenges interfere with daily life.
- Level 2 (requiring substantial support): Social and behavioral differences are more apparent. The person may speak in simple sentences, have limited interests, and struggle significantly with changes in routine.
- Level 3 (requiring very substantial support): The person has severe difficulties with communication, sometimes speaking very few words or none at all, and experiences extreme distress with flexibility and change.
These levels are not permanent labels. Someone’s support needs can shift over time with development, therapy, and changes in their environment.
What Causes Autism
Autism has a strong genetic component. Researchers have identified both rare gene mutations and common small genetic variations in autistic people, and the condition runs in families. But genetics alone don’t tell the whole story. Several environmental factors, particularly during pregnancy, are associated with higher likelihood of autism. These include advanced parental age at conception, prenatal exposure to air pollution or certain pesticides, maternal obesity or diabetes, extreme prematurity, very low birth weight, and any birth complication that temporarily reduces oxygen to the baby’s brain.
None of these factors individually cause autism. The current understanding is that autism arises from a combination of genetic predisposition and environmental influences during critical windows of brain development. No single gene or exposure accounts for more than a small fraction of cases.
Early Signs and Screening
The American Academy of Pediatrics recommends screening all children for autism at 18 months and again at 24 months. The reason for two screenings is revealing: about 32% of toddlers who are eventually diagnosed with autism appear to develop typically at 18 months and then show regression between 18 and 24 months.
Early signs parents often notice include limited eye contact, not responding to their name, delayed or absent speech, not pointing at things to share interest, repetitive movements like hand-flapping or rocking, and unusual reactions to sounds or textures. Some children hit early milestones on time and then plateau or lose skills. Others show differences from the very beginning. Early identification matters because evidence-based support started in the toddler years is linked to significantly better long-term outcomes in communication and daily living skills.
Autism in Adults and Masking
Many people, particularly women, reach adulthood without a diagnosis. One major reason is camouflaging, a set of behavioral strategies autistic people use, often unconsciously, to hide their differences in social situations. Camouflaging includes mimicking other people’s facial expressions and gestures, rehearsing conversations ahead of time, steering discussions toward familiar topics, and using humor or intelligence to compensate for social difficulty.
Women with autism tend to camouflage more than men. They may develop more conventional-sounding language skills and form friendships that look typical on the surface, making their autism less visible to clinicians. But chronic camouflaging comes at a cost. Autistic adults who mask heavily report higher rates of anxiety, exhaustion, and a fractured sense of identity. For many, a late diagnosis brings relief: it reframes a lifetime of feeling out of step as a difference in wiring rather than a personal failing.
Co-occurring Conditions
Autism rarely travels alone. ADHD is one of the most common companions, with significant overlap in attention, executive function, and sensory processing challenges. Anxiety is also extremely prevalent, particularly among those who camouflage. Epilepsy affects roughly 20% of autistic people, with higher rates among those who also have intellectual disability (about 21.5%) compared to those without (about 8%). Depression, sleep difficulties, and gastrointestinal problems are also more common in autistic people than in the general population.
These co-occurring conditions can sometimes overshadow the autism itself, leading to partial treatment that misses the bigger picture. An adult treated for anxiety alone, for example, may continue to struggle because the underlying autistic traits shaping their experience go unrecognized.
Therapies and Support
There is no single treatment for autism, and the goal of support is not to make someone “less autistic.” Instead, therapies focus on building skills, reducing barriers, and improving quality of life. The most common approaches include applied behavior analysis (ABA), occupational therapy, and speech therapy.
ABA focuses on increasing helpful behaviors and reducing those that interfere with learning or safety. It targets measurable skills like communication, social interaction, and daily living tasks such as dressing or brushing teeth. Occupational therapy helps with fine motor skills, sensory regulation, self-care, and organizational strategies. An occupational therapist might work on handwriting, teach calming techniques for sensory overload, or modify a workspace to reduce distracting input. Speech therapy addresses not just spoken language but also the social use of communication: understanding sarcasm, taking turns in conversation, or reading body language.
For many autistic adults, support looks less like formal therapy and more like workplace accommodations, structured routines, noise-canceling headphones, and social communities where they don’t need to mask.
Language and Identity
You’ll see autism described two ways: “person with autism” (person-first language) and “autistic person” (identity-first language). Research and professional guidelines have traditionally used person-first phrasing, but surveys of autistic adults show that more prefer identity-first language. The reasoning is that autism isn’t something carried separately from the person, like a backpack. It shapes how someone thinks, perceives, and experiences everything. Advocates of identity-first language see it as a point of pride rather than something to be linguistically distanced from. Both forms are used, and preferences vary from person to person.