Autism, also known as autism spectrum disorder (ASD), is a condition characterized by impairment in social communication and interaction, as well as a need or strong preference for predictability and routine, sensory processing differences, focused interests, or repetitive behaviors. Features of autism are present from early childhood and the condition typically persists throughout life. Autism is classified as a neurodevelopmental disorder, and a diagnosis requires professional assessment that these characteristics cause significant challenges in daily life beyond what is expected given a person's age and social environment. Because autism is a spectrum disorder, presentations vary and support needs range from minimal assistance to full-time, 24-hour care.
Autism diagnoses have risen since the 1990s, largely because of broader diagnostic criteria, greater awareness, and wider access to assessment. Changing social demands may also play a role. The World Health Organization estimates that about 1 in 100 children were diagnosed between 2012 and 2021, noting an increasing trend. Surveillance studies suggest a similar share of the adult population would meet diagnostic criteria if formally assessed. Autism is highly heritable and involves many genes, while environmental factors appear to play a smaller, mainly prenatal role. Boys are diagnosed several times more often than girls, with girls being better at hiding autistic traits. Conditions such as anxiety, depression, attention deficit hyperactivity disorder (ADHD), epilepsy, as well as intellectual disability, are more common among autistic people. Autistic people are also more likely to be a part of the LGBTQ community. Certain savant abilities are also more common in autistic people than in other groups.
There is no cure for autism. Several autism therapies aim to improve self-care, social, and language skills. Reducing environmental and social barriers helps autistic people participate more fully in education, employment, and other aspects of life. No medication addresses the core features of autism, but some are used to help manage commonly co-occurring conditions, such as anxiety, depression, irritability, ADHD, and epilepsy.
The idea of autism as a disorder has been challenged by the neurodiversity framework, which frames autistic traits as a healthy variation of the human condition.Kapp, Steven K. Autistic community and the neurodiversity movement: Stories from the frontline. Springer Nature, 2020. This perspective, promoted by the autism rights movement, has attracted increasing research attention, but is debated and remains controversial among autistic people, advocacy groups, healthcare providers, and charities.
In recent years, the autism spectrum has controversially been criticized as overly inclusionary by some researchers and caretakers of autistic people, who accordingly propose that autistic people able to live an independent life should be clinically distinguished from those who require continuous assistance.
Signs and characteristics Autism is primarily characterized by differences and difficulties in social interaction and communication, alongside restricted or repetitive patterns of interests, activities, or behaviors (stimming), and, in many cases, distinctive reactions to sensory input. The specific presentation varies widely. Clinicians often consider assessment for autism when these characteristics are present, especially if they are associated with difficulty obtaining or sustaining employment or education, difficulty initiating or maintaining social relationships, involvement with mental health or learning disability services, or a history of neurodevelopmental conditions (including learning disabilities and ADHD) or mental health conditions. In most cases, signs of autism are first observable in infancy or early childhood and remain throughout life. Autistic people may be significantly disabled in some respects, but average—or, in some cases, superior—in others.
Social and communication skills Autistic people may have differences and difficulties in social communication and interaction, which can lead to challenges in environments structured around non-autistic norms. Diagnostic criteria for autism require difficulties across three social domains: social–emotional reciprocity, nonverbal communication, and developing and maintaining relationships.
Social–emotional reciprocity
Common early signs of autism include little or no babbling in infancy. Difficulties may also be apparent in traditional forms of reciprocal social interaction, such as games like peek-a-boo or pat-a-cake, as well as in shared attention to objects of interest; this may distinguish autistic from non-autistic infants.
Historically, autistic children were said to be delayed in developing a theory of mind, and the empathizing–systemizing theory proposed that while autistic people may have compassion (affective empathy) for others with similar autistic traits, they often have limited, though not necessarily absent, cognitive empathy. This may present as social naïvety, lower-than-average intuitive perception of the meaning or utility of body language, social reciprocity, or social expectations, including the habitus, social cues, and certain aspects of sarcasm, which to some degree may be influenced by alexithymia. A 2019 meta-analysis found that alexithymia commonly co-occurs in autism (49.93%) and infrequently in neurotypicals (4.89%); the random effects risk ratio (6.50) was statistically significant (p<0.001).
Recent research has increasingly questioned these earlier interpretations, as the double empathy problem theory (2012) proposes that misunderstandings arise mutually between autistic and non-autistic people, rather than solely from autistic deficits in empathy or social cognition. This perspective has contributed to a growing recognition that autistic behavior and communication may reflect different, rather than deficient, social behavior and communication styles. Autistic interests and conversational styles are often characterized by a strong focus on specific topics, a phenomenon known as monotropism.
Spoken communication Differences in verbal communication often become noticeable in early childhood, as many autistic children develop language skills at an uneven pace. Speech may emerge later than is typical or not at all (non-speaking autism), while reading ability may be present before school age (hyperlexia). Infants may show delayed onset of babbling, atypical gestures, lower responsiveness, or vocal patterns that are less synchronized with caregivers. During the second and third years, autistic children may produce less frequent and less varied babbling, consonants, words, and word combinations, and may integrate gestures with speech less often. They are less likely to make requests or share experiences, and more likely to repeat others' words or phrases (echolalia). About 25–35% of autistic school-age children are non-speaking or minimally speaking. The age at which speech develops and the complexity of early language development are significant predictors of verbal communication abilities in later life.
Nonverbal communication
Autistic people often display atypical behaviors or differences in nonverbal communication. Some may make infrequent eye contact, even when called by name, or avoid it altogether because they find it uncomfortable, distracting, or overstimulating. Some autistic people say maintaining eye contact feels invasive or causes sensory overload. They may recognize fewer emotions or interpret facial expressions differently, and may not respond with expressions expected by their non-autistic peers. They can also have difficulty inferring social context or subtext in conversation or text, resulting in different interpretations of meaning. Speech characteristics such as volume, rhythm, and intonation (prosody) can vary, and atypical prosody is estimated to occur in at least half of autistic children.
Developing and sustaining relationships Signs of autism in childhood include less apparent interest in other children or caregivers, possibly with more interest in objects. Behaviors that may appear as indifference to non-autistic people often reflect autistic differences in recognizing others' personalities, perspectives, and interests. Most research has focused on interpersonal relationship difficulties between autistic and non-autistic people and on teaching social skills to address these gaps, but newer studies indicate that autistic people often form satisfying relationships with other autistic people, which can enhance quality of life.
Children on the autism spectrum are more likely than their non-autistic peers to be involved in bullying, most often as victims. Among autistic people who seek friendships, reduced friendship quality and quantity are often associated with increased loneliness. Autistic people also face greater challenges in developing romantic relationships than non-autistic people.
Over time, many autistic people learn to observe and form models of social patterns, and develop coping strategies, such as "masking". Masking is associated with poorer mental health outcomes as well as delayed diagnosis, which can limit access to appropriate supports.
Restricted and repetitive behaviors
The second core feature of autism is a pattern of restricted and repetitive behaviors, activities, and interests. To be diagnosed with autism under the DSM-5-TR, a person must exhibit at least two of the following behaviors: repetitive behaviors, resistance to change, focused interests, and sensory reactivity.
It is increasingly argued that these characteristics should be accepted, which is supported by their recognized functions, such as self-regulation. Focused interests can also provide personal fulfillment and contribute to the development of specialized knowledge. A distinction should be made between these features and those of obsessive–compulsive disorder, which can co-occur with autism and involve compulsions or obsessions aimed at preventing feared outcomes.
Repetitive behaviors Repetitive behaviors found in autism include rocking, hand flapping, finger flicking, head banging, and repeating phrases or sounds (including echolalia). These behaviors may occur consistently or primarily when the person is stressed, anxious, or upset. They are also known as stimming. Other examples include playing with toys in ways others might consider limited or unusual (e.g., arranging toys in a row).
In adults with autism, stimming is also used as a coping mechanism. Many adults learn to suppress (or "mask") these behaviors, which can increase their stress and anxiety.
Resistance to change Autistic people may have a strong preference for routine, such as performing daily tasks in a specific order or showing distress in response to changes others may consider minor. They may become distressed if their routine changes or is disrupted.
Focused interests
Autistic people may have an intense interest in a particular activity, topic, or hobby, often accompanied by sustained attention and deep knowledge; for example, a strong attachment to certain objects or frequent discussion of a certain topic.
Sensory reactivity Atypical responses may arise in autistic people in response to certain sensory input, such as aversion to specific sounds or textures, fascination with lights or movement, or apparent indifference to pain or temperature. This is experienced by 90% of autistic people. They can be hyperactive or hypoactive in response to sensory input. Some underreact to pain and temperature while others have a stronger reaction to it.
Self-injury