Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social interaction, communication, and repetitive behaviors or interests. It is called a "spectrum" disorder because the symptoms and severity can vary widely from person to person. In adults, the symptoms of ASD may manifest differently than in children and may not be as immediately apparent. Adults with ASD may have difficulty with social interactions and may struggle to understand nonverbal cues, such as tone of voice and facial expressions. They may also have a tendency towards repetitive behaviors and rigid routines, and may have difficulty with abstract concepts. Some adults with ASD may also have additional conditions such as anxiety or depression.

The diagnosis of ASD in adult is made by expert clinician, who will consider the individual's behavior, history and developmental milestones.