Psychiatry is a branch of medicine that studies and treats mental and emotional disorders. While any physician may prescribe the medications used to treat various forms of mental illness, psychiatrists are more extensively trained in differential diagnosis of mental illness and keep up to date on the newest treatment modalities for mental illness. The term alienist is an old term for a psychiatrist, and the term shrink (from head shrinker) is a (sometimes offensive) slang term for a psychotherapist.
Note that psychiatry is practiced by psychiatrists, psychology by psychologists. Psychiatrists are medical doctors and may prescribe drugs. Psychology is the broader study of behaviour and thought processes not just in the context of mental health. Clinical psychologists specialize in mental health and have extensive training in therapy and psychological testing. They do not usually prescribe drugs.
Mind versus brain
Psychiatric illnesses were for some time characterised as disorders of function of the mind rather than the brain, although the distinction is not always obvious. In the current state of knowledge this distinction does not always hold true, as many psychiatric conditions have physical etiologies.
For a long period of history, neurology and psychiatry were a single discipline, and following their division the steady advance in understanding of the basic functioning of neurons and the brain is bringing areas of the two disciplines back together.
Psychiatry was at first a pragmatic discipline that was part of general medicine, combining medicine and practical psychology. The work of Emil Kraepelin laid the foundations of scientific psychiatry, but was derailed by the psychoanalytic theories of Sigmund Freud. For many years, Freudian theories dominated psychiatric thinking.
The discovery of lithium carbonate as a treatment for bipolar disorder, followed by the development of fields such as molecular biology and tools such as brain imaging has led to psychiatry re-discovering its origins in physical and observational medicine without losing sight of its humane dimension.
Unlike most other areas of medicine, there is a politicised anti-psychiatry movement that opposes the practices of, and in some cases the existence of, psychiatry. Some opponents of psychiatry state that selective financing by large multinational drug companies of both high ranking professional psychiatrists, research and educational material has led the practice of psychiatry to be subversively, and in some cases inhumanely, misled.
Some common criticisms of the field include the notion that no cause of mental illness has ever been found. There are a number of people trained in the field who have stated that physical tests can't distinquish between a normal person and a mentally ill person.
There are also criticisms based on what is perceived as political motivations on the part of psychiatrists as opposed to objective scientific criteria. An example often cited is the removal of homosexuality from the list of mental illnesses in the DSM. Thus some critics say that a mental illness label such as schizophrenia has no etiology and is only a matter of opinion. If the addition or removal of mental illnesses from the DSM is politically based, then the DSM can not be held by all as an objective standard.
Also some people criticize the psychiatric profession for treatments that get in and out of usage. An example is ECT which the psychiatric professioned considered a barbaric practice during the 1970s and 1980s only to be revised recently as a treatment for depression.
A few prominent critics of psychology and mental illness in general include Thomas Szasz, who is the author of "The Myth of Mental Illness", and Peter Breggin, who is the author of Prozac Backlash, as well as other books criticizing the use of psychiatric drugs.
Practice of psychiatry
In the United States, psychiatrists are board certified as specialists in their field. Physicians wishing to become board certified psychiatrists will practice as residents for four years, learning the specialty before taking the psychiatry boards. In other countries, similar rules usually apply.