Consultation-liaison (CL) psychiatry refers to the skills and knowledge utilized in evaluating and treating the emotional and behavioral conditions in patients who are referred from medical and surgical settings. Many such patients have comorbid psychiatric and medical conditions, and others have emotional and behavioral problems that result from the medical illness either directly or as a reaction to it and its treatment.

Psychosomatic medicine refers to the study of “mind–body” relationship in medicine. Investigators in psychosomatic medicine have historically been interested in the psychosomatic aspects of medical patients, and were pioneer practitioners of CL psychiatry.

Imhotep, court physician and architect to King Djoser (2630–2611 BCE) of Egypt, built the Step Pyramid in Sakkhara, Egypt, some 4500 years ago, as a medical instrument to keep the king’s body through eons until his soul returned, a truly “psychosomatic” instrument. This pyramid is the oldest pyramid still standing, and Imhotep was deified as god of medicine. Ancient Chinese and Indian medicine was inherently “psychosomatic” in that the psyche and the soma were seen to be intrinsically interconnected. In Chinese medicine, excesses or deficiencies in seven emotions—joy, anger, sadness, grief, worry, fear, and fright—were commonly considered to cause disease (Rainone 2000). In Vedic medicine, certain personality components were considered to reside in particular organs, for example, passion in the chest and ignorance in the abdomen, and powerful emotions may cause peculiar behavior.

Hippocrates (470–370 BCE) was perhaps the first physician to systematize clinically the notion that psychological factors affect health and illness. In a famous, what might now be called “forensic psychiatric” opinion, Hippocrates defended a woman who gave birth to a dark-colored baby on the grounds that her psychological impression on seeing an African was sufficient to change the color of her fetus (Zilboorg 1941). Hippocrates was an excellent clinical observer of psychiatric manifestations of medical disease as shown by his detailed descriptions of postpartum psychosis and delirium associated with tuberculosis and malaria (Zilboorg 1941). Hippocrates condemned the prevailing view of epilepsy as a “sacred” disease, holding that it was a disease like any other. Though his theory of the “wandering uterus” underlying hysteria lacked scientific foundation, Hippocrates’ humoral theory of disease anticipated present-day neurotransmitters. His emphasis on climate, environment, and lifestyle in health and illness, together with his awareness of the role of psychological factors in physical health and his belief in biologic/physiologic explanations of pathogenesis, entitle him to the title of not only the father of medicine but also the father of psychosomatic medicine and the biopsychosocial approach.

With the descent of the Dark Ages, a tyrannical religious monism attributing mental and physical illness to witchcraft, and divine retribution stifled scientific inquiry. A textbook for the diagnosis (torture) and treatment (execution) of witches was the Malleus Maleficarum (The Witch’s Hammer, 1487) written by two Dominican monks, James Sprenger and Henry Kramer, and prefaced with a bull from Pope Innocent VIII.

The Hippocratic tradition in medicine was revived with the Renaissance and nourished by the Enlightenment. The French mathematician and philosopher René Descartes (1596–1650) proposed that the human body was like a machine, subject to objective investigation, while the soul or mind was a separate entity that interacted with the body in the pineal gland and that it was in the domain of theology and religion. This mind–body dualism facilitated the scientific study of the body at the expense of such studies of the mind. A number of competing and complementary theories, briefly described below, have been proposed since then to attempt to explain the nature of mind and body/matter.

Benedictus de Spinoza (1632–1677), a Dutch lens crafter and philosopher, proposed a monism called double aspect theory, that is, the mental and physical are the two different aspects of the same substance, which in his view was God. Gottfried Wilhelm Leibniz (1646–1716) proposed psychophysical parallelism, that is, mind and body exist in parallel harmony predetermined by God from the beginning. Immaterialism, as advocated by George Berkeley (1685–1753), declared that existence is only through perception of the mind, that is, the body is in the mind. On the opposite pole is materialism, which holds that matter is fundamental and that what we call mind is a description of a physical phenomenon. Julien Offroy de la Mettrie (1709–1751) advocated that human souls were completely dependent on the states of the body and that humans were complete automata just like animals as proposed by Descartes.

Epiphenomenalism, proposed by Shadworth Holloway Hodgson (1832–1912), an English philosopher, postulates that the mind is an epiphenomenon of the workings of the nervous system. Mind and emotions, being epiphenomena, cannot affect the physical, just as a shadow cannot affect a person. Thomas Henry Huxley (1825–1895) popularized this view and placed it in an evolutionary context. Double aspect monism, proposed by George Henry Lewes (1817–1878), postulates that the same phenomenon, if seen objectively, is physical, and, if seen subjectively, is mental. William Kingdon Clifford (1845–1879) coined the term mind-stuff theory. In this theory, higher mental functions, such as consciousness, volition, and reasoning, are compounded from smaller “mind-stuff” that does not possess these qualities, and even the most basic material stuff contains some “mind-stuff” so that compounding of the material stuff would produce higher order “mind-stuff.” This theory holds psychical monism—mind is the only real stuff and the material world is only an aspect in which the mind is perceived.

In spite of strong monistic trends, the major trend in medicine and psychiatry through the nineteenth and twentieth century has remained dualistic and interactional, that is, how the mind affects the body and vice versa. Johann Christian Heinroth (1773–1843) coined the term psychosomatic in 1818 in the context of psychogenesis of physical symptoms. Psychosomatic relationship in the form of hypnosis was demonstrated and exploited by Anton Mesmer (1734–1815), though he mistakenly claimed it to be magnetic in nature (“animal magnetism”). Hypnosis was revived as a subject of medical investigation, diagnostics, and treatment by two competing schools, one at the Salpetriere Hospital in Paris headed by the neurologist, Jean-Martin Charcot (1825–1893), and the other at the university in Nancy, France, led by the internist, Hippolyte Bernheim (1840–1919). Charcot believed that hypnotizability was a result of brain degeneration in hysteria, while Bernheim and the Nancy school (including Ambroise-Auguste Liebeault and Pierre Janet) believed that psychological suggestion underlay the hypnotic phenomena.

Sigmund Freud (1856–1939) learned hypnosis to treat hysteria under Charcot. Freud gave up hypnosis in favor of free association, and with this tool systematically investigated and proved the psychogenesis of somatic symptoms by reversing them with successful treatment. Franz Alexander (1891–1964) was a student of Sigmund Freud who emigrated to the USA and founded the Chicago Institute of Psychoanalysis in 1932. Alexander psychoanalyzed patients suffering from a variety of somatic illnesses, and formulated that there were seven diseases that were particularly psychosomatic: essential hypertension, peptic ulcer, thyrotoxicosis, ulcerative colitis, neurodermatitis, rheumatoid arthritis, and bronchial asthma. He postulated that specific psychological conflicts were associated with specific autonomic activation, resulting in psychosomatic disease (e.g., in peptic ulcer, repressed dependency needs stimulate gastric secretion causing ulceration). This is called the specificity theory of psychosomatic medicine. Flanders Dunbar (1902–1959), a contemporary of Alexander, believed that psychosomatic illnesses were associated with certain personality profiles and constellations rather than specific conflicts.

Peter Sifneos and John Nemiah (1971, 1973, 1996) proposed that psychosomatic disorders arose as a result of a difficulty in describing or recognizing one’s own emotions, a limited fantasy life, and general constriction in the affective life, which they called alexithymia. The concrete mode of thinking associated with alexithymia is called operational thinking or pensée opératoire. Alexithymia is postulated to be related to primitive defenses of denial and splitting, and may be associated with a disturbance in cerebral organization.