A Psychologist (PhD or PsyD) has a doctoral level degree and advanced theoretical and clinical as well as research training. A licensed psychologist may offer psychotherapy and/or psychological testing as well. Research psychologists may solely perform research and not be involved in licensed clinical work. At the time of this writing in 2006, psychologists in California are not licensed to prescribe medications, but in the future this may change.
A Psychiatric Nurse Practitioner (PNP) or Registered Nurse Practitioner (RNP) is a licensed advanced practice registered nurse qualified in medical evaluation as well as psychiatric training who works collaboratively with a medical doctor. A Psychiatric Nurse Practioner can provide psychotherapy, medical evaluation and psychiatric medication management usually through a clinic or associated with a medical practice.
A Psychiatrist (MD) is a licensed, board-certified medical doctor who specializes in psychiatry and is able to prescribe medications as well as provide psychotherapy. Some psychiatrists mainly provide medication management and refer their clients to MFTs or psychologists for therapy. Some offer both medication management and psychotherapy or solely provide psychotherapy or psychoanalysis.