Time changes all concepts. "Obsessive-compulsive disorder" is no exception. In the seventeenth century, obsessions and compulsions were often described as symptoms of religious melancholy. The Oxford Don, Robert Burton, reported a case in his compendium, the Anatomy of Melancholy (1621): "If he be in a silent auditory, as at a sermon, he is afraid he shall speak aloud and unaware, something indecent, unfit to be said." In 1660, Jeremy Taylor, Bishop of Down and Connor, Ireland, was referring to obsessional doubting when he wrote of "scruples": [A scruple] is trouble where the trouble is over, a doubt when doubts are resolved." In his 1691 sermon on religious melancholy, John Moore, Bishop of Norwich, England, referred to individuals obsessed by "naughty, and sometimes Blasphemous Thoughts [which] start in their Minds, while they are exercised in the Worship of God [despite] all their endeavours to stifle and suppress them ... the more they struggle with them, the more they encrease."

Modern concepts of OCD began to evolve in the nineteenth century, when Faculty Psychology, phrenology and Mesmerism were popular theories and when "neurosis" implied a neuropathological condition. Like ourselves, psychiatrists then struggling to understand the mentally ill were influenced by intellectual currents coursing through philosophy, physiology, physics, chemistry and political thought. Obsessions, in which insight was preserved, were gradually distinguished from delusions, in which it was not. Compulsions were distinguished from "impulsions," which included various forms of paroxysmal, stereotyped and irresistible behavior. Influential psychiatrists disagreed about whether the source of OCD lay in disorders of the will, the emotions or the intellect.

In his 1838 psychiatric textbook, Esquirol (1772-1840) described OCD as a form of monomania, or partial insanity. He fluctuated between attributing OCD to disordered intellect and disordered will. After French psychiatrists abandoned the concept of monomania in the 1850s, they attempted to understand obsessions and compulsions within various broad nosological categories. These often included the conditions we now identify as phobias, panic disorder, and agoraphobia and hypochondriasis; certain classification schemes also included sexual perversions, manic behavior and even some forms of epilepsy. Dagonet (1823-1902), for example, considered compulsions to be a kind of impulsion and OCD a form of folie impulsive (impulsive insanity). In this illness, impulsions violentes , irresistibles overcame the will and became manifest in obsessions or compulsions. Morel (1809-1873) placed OCD within the category, "delire emotif " (diseases of the emotions), which he believed originated from pathology affecting the autonomic nervous system. He felt that attempts to explain obsessions and compulsions as arising from a disorder of intellect did not account for the accompanying anxiety. Magnan (1835-1916) considered OCD a "folie des degeneres" (psychosis of degeneration), indicating cerebral pathology due to defective heredity.

While the emotive and volitional views held sway in France, German psychiatry regarded OCD, along with paranoia, as a disorder of intellect. In 1868, Griesenger published three cases of OCD, which he termed "Grubelnsucht ," a ruminatory or questioning illness (from the Old German, Grubelen, racking one's brains). In 1877, Westpahal ascribed obsessions to disordered intellectual function. Westphal's use of the term Zwangsvorstellung (compelled presentation or idea) gave rise to our current terminology, since the concept of "presentation" encompassed both mental experiences and actions. In Great Britain Zwangsvorstellung was translated as "obsession," while in the United States it become "compulsion." The term "obsessive-compulsive disorder" emerged as a compromise.

In the last quarter of the nineteenth century, the diagnostic category, neurasthenia (inadequate "tonus" of the nervous system), engulfed OCD along with numerous other disorders. As the twentieth century opened, both Pierre Janet (1859-1947) and Sigmund Freud (1856-1939) isolated OCD from neurasthenia. In his highly regarded work, Les Obsessions et la Psychasthenie (Obsessions and Psychasthenia ), Janet proposed that obsessions and compulsions arise in the third (deepest) stage of psychasthenic illness. Because the individual lacks sufficient psychological tension (a form of nervous energy) to complete higher level mental activities (those of will and directed attention), nervous energy is diverted into and activates more primitive psychological operations that include obsessions and compulsions.

Freud gradually evolved a conceptualization of OCD that influenced and then drew upon his ideas of mental structure, mental energies, and defense mechanisms. In Freud's view, the patient's mind responded maladaptively to conflicts between unacceptable, unconscious sexual or aggressive id impulses and the demands of conscience and reality. It regressed to concerns with control and to modes of thinking characteristic of the anal-sadistic stage of psychosexual development: ambivalence, which produced doubting, and magical thinking, which produced superstitious compulsive acts. The ego marshalled certain defenses: intellectualization and isolation (warding off the affects associated with the unacceptable ideas and impulses), undoing (carrying out compulsions to neutralize the offending ideas and impulses) and reaction formation (adopting character traits exactly opposite of the feared impulses). The imperfect success of these defenses gave rise to OCD symptoms: anxiety; preoccupation with dirt or germs or moral questions; and, fears of acting on unacceptable impulses.

As the twenty-first century begins, advances in pharmacology, neuroanatomy, neurophysiology and learning theory have allowed us to reach a more therapeutically useful conceptualization of OCD. Although the causes of the disorder still elude us, the recent identification of children with OCD caused by an autoimmune response to group A beta-hemolytic streptococcal infection promises to bring increased understanding of the disorder's pathogenesis.