of Social Work (M.S.W.) . Psychiatrist: Physicians ( M.D. , DO ,) who treat mental illness. Subspecialties include: Addiction , child and adolescent psychiatry , emergency , forensic , neurodevelopmental disabilities , and neuropsychiatry. Psychiatric Nurse : Licensed Practical Nurse (L.P.N.), Registered Nurse (R.N.), or Advanced Practice Registered Nurse (A.P.R.N., requires