"Consults" occur when the primary care team has questions about a patient's mental health, or how that patient's mental health is affecting his or her care and treatment. The psychiatric team works as a "liaison" between the medical team and the patient. Issues that arise include assessing the capacity of a patient to consent to treatment, attempting to settle conflicts between patients with the primary care team, and the intersection of problems in both physical and mental health, as well as patients who may report physical symptoms as a result of a mental disorder, and assessing patietns for abnormal illness behaviour. Delirium is commonly diagnosed and treated by psychiatrists. Finally, patients who have attempted suicide and subsequently admitted for medical treatment are generally treated by this field.
In some hospitals, the Consultation-liaison psychiatry team also covers psychiatric presentations to the Emergency Department, while in others doctors from the psychiatric unit will cover this area.
Edward Billings first coined the term "liaison psychiatry." The publishing of two texts A Handbook of Elementary Psychobiology and Psychiatry, by Billings, and Psychosomatic Medicine, by Edward Weiss and O Spurgeon English, outlined the theoretical foundations for the developing field. George L. Engel is considered to have been one of the most important figures in the development of liaison psychiatry and coined the term "Biopsychosocial Model" which overcame divisions created by Cartesian Dualism and was to have wider repercussions on psychiatric practice.
In the United Kingdom, the Faculty of Liaison Psychiatry was established within the Royal College of Psychiatrists in 1997. The European Association for Consultation Liaison Psychiatry and Psychosomatics also produced a set of guidelines for training in Liaison Psychiatry. The American Psychiatric Association formally recognized C-L psychiatry as a subspecialty in 2004, with its own sub-specialty board exam. The profession debated about the best term for this specialty, finally settling on "Psychosomatic Medicine".