Psychiatry is a branch of medicine dealing with the diagnosis, treatment, and prevention of mental and emotional disorders. Psychology is the science of mind and behavior. A psychiatrist is a medical doctor. Psychologists may work with patients in a variety of therapeutic contexts, but they generally can’t prescribe medication (at least in the U.S.).
Examples
The board suspended the doctor from practicing psychiatry and ordered him to take a medical ethics class. [WCTV.tv]
In one remarkable passage, Hillenbrand delves into the psychology of revenge. [Guardian]
The psychiatrist recommended that Solanki, who knew little about SAD at the time of his diagnosis, begin using an antidepressant drug. [Reading Eagle]
But one university psychologist has warned this is wreaking havoc with our self-image and undermining our sense of self-worth. [Daily Mail]