Autism (called autism spectrum disorder, or ASD, in medical texts) is a complex neurodevelopmental condition that affects how people communicate, interact, learn, and behave. People with autism often have challenges with social communication and interaction. They may also have highly focused interests, show inflexible behaviors, respond differently to sensory information, and have different ways of moving or focusing their attention. These features can range from mild to extreme. Some individuals need significant support in daily life, while others live and work independently.

Autism is a lifelong condition that affects people of all backgrounds. In the United States, around 3% of children aged 8 years have autism, according to the U.S. Centers for Disease Control and Prevention (CDC). The condition is more than three times as common in boys as in girls. Features of autism usually appear before age 3, but they may be recognized earlier or later depending on the individual.

Early diagnosis and personalized supports or therapies can make a significant difference in a child’s development and later independence and quality of life. Even when diagnosed in adulthood, appropriate support and therapies can help autistic people develop new skills, reduce challenges, and improve daily functioning.

Autism is a developmental condition that affects the growth and function of the brain and nervous system, resulting in differences in how people communicate, interact with others, and process information. Changes in brain development and structure can alter these networks. This can lead to differences in the number and organization of neurons, especially in regions of the brain involved in emotions, social behavior, and language. These differences can make it more difficult to understand social cues, communicate, and adapt to change.

The core diagnostic features of autism include difficulties with social skills, communication, repetitive behaviors, highly focused or unusual interests, and over- or under-responsiveness to sensory information. These characteristics can affect a person’s ability to participate in conversations, form relationships with other people, and manage changes in their surroundings.

Autism is described as a “spectrum” because autistic people can have a wide range of abilities and challenges, and each person’s experience is unique. Some autistic individuals have intellectual disabilities, while others have average or above-average intelligence. Some have language delays and differences that affect learning but have strong abilities in other areas, including music, math, or memory.

Autism is usually identified in early childhood, often before age 3, but it can be recognized at any age. For a diagnosis of autism, it is important that features are evident during early childhood. The condition usually lasts throughout a person’s life, and the level of support needed can vary greatly from one individual to another.

Scientists don’t fully understand what causes autism. It results from a combination of genetic and environmental factors that influence early brain development.

Genetic factors play a major role in autism, and scientists have recognized for decades that autism runs in families. Changes in many different genes can increase the likelihood of developing autism. Most of the genes linked to autism affect brain development, including the growth and organization of neurons and the connections between them. In around 10% to 20% of people with autism, specific gene mutations or chromosomal abnormalities directly cause autism, typically as part of a syndrome that causes other health issues. However, in most cases of autism, the specific genetic cause is not currently identifiable.

Environmental factors may also contribute to autism, especially in people who are already genetically susceptible. These can include advanced parental age, certain complications during pregnancy and birth, very low birth weight, and other factors researchers are still studying.

It is important to note that vaccines or their ingredients do not cause autism, and extensive research has found no link between vaccination and autism. Likewise, there is no evidence of a causal link between acetaminophen and autism.

Factors associated with autism include:

• Having a first-degree relative with autism
• Having certain genetic or chromosomal conditions, such as fragile X syndrome, tuberous sclerosis, or Down syndrome
• Having older parents
• Certain complications during pregnancy and birth
• Very low birth weight
• Premature birth
• Short or long intervals between pregnancies
• Being male

Diagnostic features of autism include:

• Difficulty with social communication and interaction
• Limited or inconsistent eye contact
• Not responding to one’s name
• Delayed or atypical development of language
• Trouble understanding or using facial expressions, gestures, or body language
• Difficulty developing and maintaining relationships
• Difficulty or disinterest in pretend play or imaginative activities
• Repetitive behaviors, such as hand-flapping, rocking, or repeating words or phrases
• Insistence on sameness or routines and distress with changes or transitions
• Strong attachment to or focus on certain objects, routines, or interests
• Unusual reactions to sensory input, such as sounds, lights, textures, or smells

There are other characteristics that, though not part of diagnostic criteria, are often observed in autistic people:

• Delayed motor skills
• Hyperactive, impulsive, or inattentive behavior
• Unusual eating or sleeping habits
• Mood changes, anxiety, or excessive worry
• Lack of fear or more fear than expected
• Seizures or epilepsy
• Gastrointestinal issues, such as constipation

Developmental screening is often the starting point for a diagnosis. Health care providers may use developmental screening tools, which are questionnaires or checklists, such as the Modified Checklist for Autism in Toddlers (M-CHAT), that assess communication, social skills, and behaviors. These tools help identify children who should receive a more comprehensive evaluation.

Diagnosis can take place in many different health care settings, from a pediatrician’s office to a specialized clinic. The most thorough diagnostic assessment entails a comprehensive evaluation, which is often conducted by a team of specialists that may include pediatricians, psychologists, speech-language pathologists, and neurologists.

A clinician will review a patient’s family and medical history, often by speaking with a caregiver. This can help in identifying factors that could increase the likelihood of developing autism or help explain reasons why the symptoms may not indicate autism. The clinician may also ask about the patient’s developmental history and milestones, communication skills, social interaction abilities, and behavior. For example, they may ask about how a child plays, speaks, or interacts with others, and when symptoms were first observed or if there was a plateau or regression in development. This type of information may not be acquired when the person being evaluated is an adult.

During the assessment, the clinician will observe behavior, communication, and social interactions, and may look for signs such as limited eye contact, delayed language, or repetitive movements.

This in-depth evaluation also involves standardized diagnostic tools along with cognitive and language assessments to evaluate intellectual abilities and the ability to use and understand language.

Additional tests may be recommended to help make a diagnosis, to guide support or therapies, or to rule out other conditions, including:

• Genetic testing: This type of testing can be used to identify genetic conditions associated with autism, such as fragile X syndrome or other chromosomal abnormalities.
• Neurological evaluation: A referral to a neurologist may be recommended, especially if there are concerns about seizures, which can co-occur in autistic people.
• Hearing tests: These tests can rule out hearing loss as a cause of language or communication difficulties and are often done before or during the evaluation process.

These assessments help clinicians measure the specific features, behaviors, and developmental patterns that can establish a diagnosis of autism. At present, there are no medical or biological tests, such as blood tests or brain scans, to diagnose autism.

Early and individualized interventions can help reduce challenges, build skills, and improve quality of life. Intervention plans are tailored to each person’s unique strengths and challenges and often involve a team of professionals working together with individuals and families. The goal of supports for autistic people is to maximize quality of life by enhancing independence and self-sufficiency.

Common supports for autism include:

• Behavioral interventions: These therapies, such as applied behavior analysis (ABA), focus on teaching new skills through systematic application of positive incentives. They are often highly structured and individualized to help children develop communication, social, and daily living skills.
  
  Common ABA-based approaches include:
• Discrete trial teaching, DTT: step-by-step teaching with positive reinforcement
• Early intensive behavioral intervention, EIBI: intensive, individualized instruction for young children
• Positive behavior support, PBS: identifies why behaviors happen and changes environments and teaches skills to encourage appropriate behavior
• Pivotal response therapy, PRT: targets pivotal skills such as motivation and starting communication to support broader learning
• Early Start Denver Model, ESDM: combines behavioral and developmental principles to promote social communication, play, and adaptive skills in different situations
• Speech-language therapy: This therapy targets multiple aspects of communication, including receptive language (understanding words and instructions), expressive language through spoken or alternative communication methods, and pragmatic language skills for social interaction.
• Occupational therapy: Occupational therapists help people develop skills for daily living, such as dressing, eating, and managing sensory sensitivities.
• Social skills development: These programs help children, adolescents, and adults develop skills in interacting with others, understanding social cues, and building relationships.
• Cognitive behavioral therapy (CBT): CBT can help people with autism manage anxiety, depression, and other emotional challenges by teaching coping and problem-solving skills.
• Educational and school-based therapies: Individualized education programs (IEPs) and specialized teaching strategies support learning and participation in school.
• Parent-mediated therapy: Parents are taught to use therapeutic techniques at home to support their child’s development and manage behaviors.
• Medication: While no medication treats the core social-communicative characteristics of autism, certain medications may help manage associated symptoms such as hyperactivity, irritability, aggression, anxiety, or sleep problems. These may include stimulants, antipsychotics, antianxiety medications, or melatonin, depending on the person’s needs.
• Physical therapy: Physical therapy can improve motor skills, coordination, and physical fitness.

A combination of these approaches can often help autistic people and improve their ability to learn, function, and participate more fully in daily life.

Autistic people may be at increased likelihood for certain complications, including:

• Anxiety and depression: Autistic people have higher rates of mood and anxiety disorders compared to people without autism.
• Attention-deficit/hyperactivity disorder (ADHD): Some people may have difficulty with attention, hyperactivity, or impulsivity.
• Intellectual disability: Some individuals may have below-average or delayed intellectual and adaptive functioning.
• Epilepsy or seizure disorders: Autistic people, especially those with intellectual disability, may have an increased risk of seizures.
• Sleep problems or unusual sleeping habits: Some autistic people have difficulty falling or staying asleep or awake at unusual hours.
• Unusual eating habits: Some autistic people engage in eating patterns that may affect nutrition and overall health.
• Gastrointestinal issues: Autistic people may have problems such as constipation or abdominal discomfort, especially if they have restricted eating habits.
• Obsessive-compulsive disorder and other psychiatric conditions: Autistic people have a higher risk of certain mental disorders.
• Self-injurious behaviors: Some individuals engage in behaviors such as head-banging or self-hitting.
• Aggression: Some autistic people have episodes of aggressive behavior toward others.
• Difficulty with motor coordination: Some people experience challenges with movement, balance, or posture that can make it difficult to play sports or stay active.
• Social isolation: Autistic people may have trouble forming and maintaining relationships, which can lead to loneliness.
• Increased risk of suicide: Autistic people have higher rates of suicide attempts and death by suicide compared to the general population.
• Reduced independence in adulthood: Some adults may need ongoing support with daily living, employment, or housing.

While autism is diagnosed based on distinctive social-communicative challenges and restricted and repetitive behaviors, strengths are also common, such as heightened perception, reasoning, memory, and focused exploration.

• Pattern Recognition: Autistic people may excel at identifying and analyzing patterns across visual, auditory, and numerical domains.
• Attention to Detail: Strong perceptual focus on fine-grain or detailed information over global patterns.
• Focused Interests and Expertise: Deep, sustained interests may lead to advanced knowledge and skills in specific topics. These strengths may translate to academic or vocational achievement.
• Semantic (Fact-Based) Memory: Autistic individuals may display strong semantic memory, or an ability to recall facts, details, and specific information.

Outcomes for autistic people can vary widely depending on factors such as the nature of challenges experienced, intellectual abilities, language skills, and the presence of other health conditions. Many autistic people flourish independently, pursue higher education, and maintain employment. Some people may need significant support throughout their lives. Early diagnosis and individualized interventions can help many autistic people develop important skills and improve their ability to function independently.

As autistic people grow older, they may continue to face challenges with social relationships, communication, and adapting to new situations. Some may experience ongoing difficulties with anxiety, depression, or other mental health conditions, and a portion of adults may require ongoing support with daily living, employment, or housing.

In recent years, scientists and clinicians have made important advances in supporting autistic people, and increasing numbers of autistic people lead independent lives, build relationships, and participate in their communities.

“Yale has been a leading clinical center for autism for more than 40 years,” says James McPartland, PhD, a Yale Medicine clinical psychologist who specializes in assessing and supporting children, adolescents, and adults with autism spectrum disorder and other developmental abilities. “Our clinical approach focuses on bringing together specialists with complementary expertise and a shared focus on autism. Teams of psychologists, physicians, speech and language pathologists, social workers, and others work directly with autistic people and, when appropriate, caregivers, over multiple days. In this way, we develop a deep and nuanced understanding of a person’s strengths and vulnerabilities that is applied to recommend specific supports and therapeutic approaches designed to meet the priorities of the individual. A key part of Yale’s approach is the collaboration of clinical providers and scientists. Our objective is to develop new insights and strategies through research so that our clinicians can deliver their benefits directly to families.”