Psychiatrist vs. Psychologist

The difference between the two mental health professional is in nature of treatment. Psychologist primarily aids the depressed patient by counseling and psychotherapy. A psychiatrist may also perform psychotherapy; but, in addition, can prescribe medications and perform ECT (electroconvulsive therapy).

Because psychiatrists are trained medical doctors, they can prescribe medications, and they spend much of their time with patients on medication management as a course of treatment. A psychiatrist is a Medical Doctor (M. D.). Psychologists are mental health professionals who hold a doctorate (Ph.D. or Psy.D.) and be called "doctor"; but, are not medical doctors (M. D.). 

Psychologist's training and education includes graduate study for at least six years in human behavior, therapeutic treatment of emotional problems,  theories of  personality, psychological test construction and administration, experimental research,  statistical analysis of data, as well as a clinical internship. Psychologists focus extensively on psychotherapy and treating emotional and mental suffering in patients with behavioral intervention. Psychologists are also qualified to conduct psychological testing, which is critical in assessing a person's mental state and determining the most effective course of treatment.