Autism Spectrum Disorder, or autism, affects one in every 100 children, according to the World Health Organization. A developmental condition caused by differences in the brain, it can affect how a person absorbs, processes and responds to information. It is usually categorised along a spectrum, from mild to severe. In the Diagnostic and Statistical Manual of Mental Disorders (DSM 5), published by the American Psychiatric Association, this spectrum is divided into levels 1, 2 and 3, where those with level 3 autism require "very substantial support". Within those categories, there is a huge diversity of needs and experiences, as well as some common traits.