Obsessive-compulsive disorders are very damaging illnesses; they can already appear in childhood and adolescence and become extremely chronic. With an average prevalence from 1-3%, they are among the most common psychiatric disorders in children and adolescents. 40% of diagnosed children and young adults display persistent and increasingly chronic symptoms and O-C disorders are highly complex syndromes with broadly varying manifestations. They arise from obsessive thoughts (ideas/thoughts or impulses, often senseless or tortured, that impose themselves or intrude) and obsessive behavior (ritualized patterns that must be frequently repeated).