A psychiatrist is a physician (M.D. or D.O.) who specializes in the diagnosis, treatment, and prevention of mental illnesses and substance use disorders. It takes many years of education and training to become a psychiatrist: He or she must graduate from college and then medical school, and go on to complete four years of residency training in the field of psychiatry. (Many psychiatrists undergo additional training so that they can further specialize in such areas as child and adolescent psychiatry, geriatric psychiatry, forensic psychiatry, psychopharmacology, and/or psychoanalysis.) This extensive medical training enables the psychiatrist to understand the body's functions and the complex relationship between emotional illness and other medical illnesses. The psychiatrist is thus the mental health professional and physician best qualified to distinguish between physical and psychological causes of both mental and physical distress. Psychiatrists are the only mental health professionals who can prescribe medications and admit to hospitals.
Information from the American Psychiatric Association