There are many excellent career options available for people wanting to work in the field of mental health. Here are some links to professional associations that provide information on these careers, the differences in them, and what training they require:
Psychiatry - Requires an undergraduate and medical degree, then 4-5 years of postgraduate training. Information for medical students considering a career in Psychiatry can be found is available from the American Psychiatric Association. Information about preparing for, applying to and attending medical school is available from the University of Kentucky College of Medicine and the Association of American Medical Colleges.
Psychology - Undergraduate degree alone or with graduate and sometimes post-graduate training are required for the various sub-specialties of Psychology. Psychology is a science concerned with human and nonhuman animal behavior and there is a wide spectrum of careers related to psychology. Information about careers and training are available from the American Psychological Association.
Social Work - Undergraduate alone or with graduate and sometimes post-graduate training are required for the various careers in Social Work. Information about careers and training are available from the American Sociological Association and the National Association of Social Workers.
Nursing - There are nurses who specialize in mental health work. To obtain more information about these careers, go to the American Psychiatric Nurses Association.