Autism spectrum disorder (ASD) is a neurological disorder (a "brain" disease) characterized by the presence of persistent (ongoing) communication and social issues. It is a developmental disorder, which begins in early childhood and continues throughout life. Autism spectrum disorder affects most every aspect of life along the way. Cognitive (thinking and language) and social skills are typically developmentally delayed compared to their peers without the disorder. However, their motor (movement) skills develop in a more typical way.Specific social interaction, communication and behavioral problems must be present before the diagnosis can be made. Though all people with autism show the same overall pattern of impairments, the severity of these issues will vary from case to case. Some people show mild impairments and others have more severe issues.From a very early age, children with autism spectrum disorder demonstrate difficulties in interacting with other people. They also have trouble with processing social and non-verbal forms of communication, such as eye contact and facial expression. For instance, a typical infant is generally responsive to adult caregiver facial expressions and will imitate those expressions. If a parent smiles at the infant, that infant is likely to smile back. This is not the case with infants on the autism spectrum as they often lack the ability to recognize facial expressions or socially expressed feelings. Children with autism spectrum disorder are also often delayed (sometimes severely so) in their development of spoken language and conversational skills.People on the autism spectrum also tend to demonstrate odd or socially inappropriate behaviors. They frequently show little interest in others and remain isolated from their surroundings. Many obsess or fixate on certain objects or on specific topics that they find personally interesting. They may insist on talking about a topic they find fascinating even when others around them are not interested. They may act out odd stereotyped movements and gestures. They may have an intense need for order and sameness in their environment and react with temper tantrums when their preferred order is changed. In general, they lack social awareness, which makes it difficult or impossible for them to successfully deal with everyday situations.Symptoms of autism spectrum disorder are not present from birth. Most children with autism spectrum disorder appear to develop normally during the first year of life. The communication symptoms of autism spectrum disorder usually become apparent between eighteen and twenty-four months of age. They can become noticeable during the first twelve months if developmental symptoms are severe. The behavioral symptoms usually first appear in early childhood. No race or social class tends to be on the spectrum more frequently than another. However, it is far more likely (as much as four to five times more likely) to be diagnosed in males than it is in females.Once established, autism spectrum disorder symptoms continue into adulthood. The symptoms range in severity (across people) from relatively mild to severe and crippling. In all but mild cases, autism interferes with normal development and makes it difficult or impossible for affected adults to live and work independently. Though intervention cannot reverse the course of autism, it can result in symptom improvement and a greater ability for independence.