Autism

The National Autistic Society defines Autism as:

A lifelong developmental disability that affects how people perceive the world and interact with others. Autistic people see, hear and feel the world differently to other people. If you are autistic, you are autistic for life; autism is not an illness or disease and cannot be 'cured'. Often people feel being autistic is a fundamental aspect of their identity.
Autism is more common than people realise with around 700,000 people living with the condition, affecting 2.8 million family members in one way or another.
While people can show signs of learning disabilities, mental health issues or other conditions, Autism is considered a hidden disability and does not affect every person in the same way. This is due to the fact that Autism is classed as a spectrum that includes other conditions such as Asperger’s syndrome and Pathological Demand Avoidance (PDA).
Source: autism.org.uk