Autism, also known as autism spectrum disorder (ASD), is a condition characterized by differences or difficulties in social communication and interaction, a need or strong preference for predictability and routine, sensory processing differences, focused interests, and repetitive behaviors. Characteristics of autism are present from early childhood and the condition typically persists throughout life. Autism is classified as a neurodevelopmental disorder, and a formal diagnosis requires professional assessment that these characteristics cause significant challenges in daily life beyond what would be expected given a person's age and social environment. Because autism is a spectrum disorder, presentations vary and support needs range from minimal to the person being non-speaking or needing 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, and conditions such as anxiety, depression, attention deficit hyperactivity disorder (ADHD), epilepsy, and intellectual disability are more common among autistic people.
