The simplest way to describe the difference between a psychologist and a psychiatrist when it comes to treating depression is that one is a medical doctor, while the other is not.
A psychologist primarily aids the depressed patient through counseling and psychotherapy. He may hold a doctoral degree (Ph.D.) and be called "doctor," but is not a medical doctor (M.D.).
A psychiatrist, on the other hand, is a medical doctor, and while he may also perform psychotherapy, he can additionally prescribe medications and perform medical procedures such as electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS).
There is an exception to the above, however. Two states -- Louisiana and New Mexico -- do allow appropriately trained clinical psychologists to prescribe medication with certain limitations.
Related articles:
- What Do All Those Initials After My Doctor's Name Mean? (Degrees, Licenses and Certifications)
- What Is the Best Kind of Doctor for Treating Depression?
- Frequently Asked Questions About Psychotherapy
- What's the Difference Between Counseling and Psychotherapy?
Source:
Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, 2010-11 Edition, Psychologists. Accessed April 18, 2011.

