Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by persistent challenges in social communication and interaction, alongside restricted, repetitive patterns of behavior, interests, or activities
. It affects how individuals perceive and interact with the world, causing difficulties in social situations, communication, and behavior regulation
. ASD is called a "spectrum" because it manifests in a wide range of symptoms and severity. Some individuals may be nonverbal, while others have proficient spoken language; some require significant support in daily life, while others live independently
. The condition typically appears in early childhood, often before age 3, though signs can sometimes be noticed in the first year of life or become apparent when a child starts school
. The causes of autism are not fully understood but are believed to involve a combination of genetic and environmental factors, with autism being highly heritable and polygenic
. It is more commonly diagnosed in boys than girls
. ASD is lifelong, but early diagnosis and intervention can significantly improve outcomes, helping individuals develop skills and supports tailored to their needs
. The condition includes what were previously separate diagnoses such as Asperger's syndrome, now all considered part of the autism spectrum
. In summary, autism spectrum disorder is a lifelong developmental condition affecting social communication and behavior, with wide variability in how it presents and the level of support needed by each individual
