Both psychiatrists and psychologists are concerned with mental health and human behavior. But there are some key differences between the two, primarily involving education, training, and the style of interaction with patients. A psychiatrist is a physician who's attended medical school and trained in general medicine, earning an M.D. or D.O. degree. Medical school is followed by a four-year residency in psychiatry, such as working in the psych unit of a hospital. As a medical doctor specializing in the treatment of mental or behavioral disorders, a psychiatrist has the authority to write prescriptions. Instead of attending medical school, psychologists earn a doctorate degree in psychology. Graduate school includes the study of psychological problems, the science of psychological research, psychological testing and the diagnosis of mental and emotional disorders. After graduate school, internships provide experience in treatment methods, analytical testing and behavioral therapy. Typically, one-to-two years of practical work experience is required to become licensed as a clinical psychologist. However, because psychologists are not medical doctors, they need to refer patients requiring medication to a psychiatrist or another M.D. Differences in the way psychiatrists and psychologists practice exist, also. Psychiatrists typically address a variety of clinical issues related to mentally ill patients, while psychologists tend to be most extensively involved in their patients' emotional lives. A psychiatrist sometimes interprets laboratory tests and brain imaging studies, besides monitoring the effectiveness of a patient's medication. So psychiatrists are more likely to treat patients with bipolar disorder, major depression or schizophrenia, which require medication to control symptoms. While psychiatrists treat the medical aspects of these illnesses, psychologists simultaneously address the emotional aspects, therapeutically helping patients gain insight, develop coping skills, reduce stress and resolve interpersonal challenges. Psychologists also conduct evaluations, provide psychotherapy and execute behavioral interventions in order to treat the emotional and mental suffering of their patients. Psychiatrists and psychologists play significant roles in understanding human behavior with the common goal of helping patients feel better.