The two main types of professionals who treat psychological problems are psychiatrists and psychotherapists. Psychiatrists are medical doctors (they have the letters M.D. after their names) who specialize in treating mental illness and who can prescribe psychiatric medication. Psychotherapists are professionals who provide psychotherapy (or ‘talk therapy’). Psychotherapists may be psychologists, social workers, counselors, nurses, family and marital therapists, or some other profession.