A Psychiatrist is a medically-trained practitioner who completes the requirements for a M.D. and who typically uses medicine to target physiological change as a first-line of treatment for behavioral/psychological problems.  Training involves 4-years of medical school followed by 3-4 year residency.  The majority of training involves assessment, diagnosis, and treatment using a biological medical model conceptualization of behavior.  Some psychiatrists also conduct scientific research and/or work primarily in academia.

A Psychologist is an academically-trained practitioner/researcher who completes the requirements for a Ph.D. or Psy.D. and who typically uses psychotherapuetic methods of treatment.  Training involves 5-6 years of graduate school followed by 1-year residency/internship.  The majority of training involves assessment, diagnosis, and treatment using a biopsychosocial conceptualization of behavior.   Licensed psychologists typically do not have prescription privileges, however, limited privileges are available in several states.   Some psychologists conduct scientific research and/or work primarily in academia.