What is the difference between a psychologist and a psychiatrist?

One essential difference is that a psychiatrist can prescribe medication and a psychologist cannot. Clinical psychologists have specialized training in the practical application of psychological knowledge, including psychological testing and evaluation. In essence, this training focused on training in psychotherapy. Psychologists typically spend 4 years in graduate school plus 1 year of a clinical internship and another year of further training prior to becoming licensed. Psychiatrists attend medical school and then complete a 4 year residency in psychiatry. Some complete fellowships after residency to further specialize in their field.