Short answers, pulled from the story.
Psychiatry is the medical specialty devoted to the diagnosis, treatment, and prevention of mental disorders, including conditions affecting cognition, perception, mood, emotion, and behavior. It treats disorders conventionally divided into mental illnesses, severe learning disabilities, and personality disorders.
The German physician Johann Christian Reil coined the term psychiatry in 1808. It literally means the medical treatment of the soul, combining the Greek word for soul with the word for medical healing.
Psychiatrists are physicians who complete a residency in psychiatry, usually four to five years, with medical training identical to that of all other physicians. This means psychiatrists can prescribe medication, order laboratory tests, order neuroimaging, and conduct physical examinations, unlike psychologists.
In 2013, Thomas Insel, then director of the National Institute of Mental Health, stated that the DSM lacks validity because diagnoses are based on consensus rather than objective laboratory measures or biomarkers. The serotonin chemical imbalance theory once used to market antidepressants is also no longer considered substantiated.
Three main diagnostic manuals are in use today. The ICD-11 is published by the World Health Organization and used worldwide, the Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and is the main tool in the United States, and the Chinese Society of Psychiatry produced the Chinese Classification of Mental Disorders.
In the past, psychiatric patients were often hospitalized for six months or more, but average stays have decreased sharply since the 1960s in a trend known as deinstitutionalization. Today the average hospital stay is around one to two weeks, though in Japan psychiatric hospitals continue to keep patients for long periods.