Anxiety disorders of which Obsessive Compulsive Disorder is one, are formed and controlled by the Amygdala, a small organ in the subconscious part of the brain which is responsible for the anxiety response. Normally, this anxiety 'switch' is in the anxiety OFF position until required for appropriate anxious reactions BUT when this 'switch' becomes stuck ON after stress or bereavement for example, the 'normal' anxiety level is raised and anxiety disorders such as Obsessive Compulsive Disorder become evident.
