Functional disorders

In clinical psychology and psychiatry functional disorders are disorders that are thought to be caused by psychological factors and are not organic in nature, that is there is no identified physiological or anatomical cause. The term 'functional' can have two implications:
 * that it is a disorder in which the functioning of an organ or organ system is abnormal.
 * and/or that this serves a psychological function in some way.

Status
Whether a given medical condition is termed a functional disorder depends in part on the state of knowledge. Some diseases, including epilepsy, schizophrenia, and migraine headaches were once considered functional disorders, but are no longer generally classified that way.