Attention deficit hyperactivity disorder (ADHD)
Attention deficit hyperactivity disorder (ADHD, also known as ADD) is characterised by symptoms including inattention, hyperactivity and impulsive behaviour.
People with this syndrome make involuntary repetitive sounds and movements. Most don't need treatment, and relaxation exercises may reduce symptoms.
Williams syndrome can cause development, learning and medical problems, although children with it often have well-developed language and music skills.
Trichotillomania is a psychiatric disorder that compels people to pull out their hair. Lasting for several months or many years, it can fluctuate in severity.