Is there really much of a difference anymore?
I mean I know a psychiatrist is an MD (or a DO) but my dictionary says they treat mental illness whereas a psychologist studies mental illness.
But it seems like now a days the fields overlap and the basic difference is one can prescribe medicine and one can’t.
Well, from what little direct example I have seen, many psychiatrists do very little in the way of psychological therapy. Most of the psychiatrists I have seen in action are primarily managing the psychiatric medications that their patients take. On the other hand, a clinical psychologist is primarily a therapist. I recall one psychiatrist actually referring a patient to see a psychologist in addition, because she felt the patient needed therapy.
Part of that may simply come from the fact that a psychiatrist’s time is a lot more expensive than a psychologist’s, thus patients really want their psychiatrists to do what no others are qualified to do-- prescribe the pills.
Lessee…a psychiatrist is an M.D. who specializes in treating mental illness (in the broadest sense). He/she can do anything any other M.D. can do, but usually focuses on psychotherapy. At one time, all psychiatrists were Freudians (Siggy having founded the specialty) but that I believe is no longer true.
A psychologist is a professional in the field of psychology. (Tautological, but the only valid definition.) A clinical psychologist is the one that takes you through sessions of therapy. There are also ones that do psychological research, ones that serve as consultants to companies, etc.
Other mental health professionals include the psychiatric social worker and the licensed psychotherapist. Non-professionals include the psychic and the psychotic. 
At a practical level – a psychiatrist is an MD, and so can prescribe medications, and so can combine medication and talk therapy. A psychologist is not an MD, and so cannot prescribe medications, but can only engage in talk (and similar) therapy.
I think Undead Dude is right, that with the advent of so many medications in the last decade (roughly) that are useful in many mental illness, some psychiatrists primarily engage in medication-therapy nowadays. The state of managed health care in the U.S. also tends to push people towards medication which is far cheaper than talk-therapy.
IMHO, there are many stresses where talk-therapy is the most satisfactory resolution. There are diseases where medication (combined with talk-therapy) is the best treatment. Rarely would medication alone be satisfactory, I think: diagnosis of the ailment usually comes late in the process, so that defense mechanisms have been built up that are best re-directed by talk therapy.
Example: my wife is bipolar (manic depressive), but that wasn’t diagnosed until she was over 30 years old. Medication has saved her life (and my sanity), and she has been well-balanced for over a decade now. But she had built up a number of defense mechanisms during those first 30-plus years, that the medication doesn’t deal with – that needs talk-therapy.
As Polycarp and Dex both pointed out, a psychiatrist has an MD (my husband is a psychiatrist, so I know more about the subject than I need to). This means that they have studied brain anatomy and brain chemistry and things like that, and they understand how the brain works (on a biochemical level). Psychologists generally don’t have this kind of knowledge; it’s not part of the curriculum.
My husband agrees with Dex that talk therapy is an important part of the process. For starters, it’s critical in correctly diagnosing the problem (always important when you’re messing around with psychoactive drugs!)
The Cat In The Hat
My personal experience (with depression) was that the therapy helped me to understand and overcome the problem, but the medication gave me enough of a lift to make me want to try.
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
I should add that I talked mostly with psychologists but I saw a psychiatrist for the initial prescription for medication. Now my regular M.D. renews the medication, adjusts dosage, etc.
“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham
Thanks guys but just so my Osteopathic friends don’t yell again a Psychiatrist isn’t always an MD he can be a DO as well. 
A psychiatrist, in order to get a license, has to see another psychiatrist extensively first. Yep.
When I was about to go to college, I went to a friend of my parents’ who was a mental health professional (don’t remember which flavor) to find out the different types and determine which I wanted to be. That year in freshman psych, I got the exact same info:
Psychiatrist & psychologist are legal terms - note this may have changed some, but I haven’t heard of any changes.
In order to call yourself a psychiatrist, you must have a degree in medicine and do an internship with another psychiatrist.
In order to call yourself a (clinical) psychologist you must have a Phd in Psychology and pass a state sponsored exam. This is Texas, it may be different in other places. (And you may only need a Masters, but I doubt it)
In order to call yourself a counselor or a therapist, you have to rent an office and put a sign up.
Note that none of the above criteria guarantee that a mental health professional will be good, or even up to speed on current research. The best therapist I’ve had is neither a psychiatrist nor a psychologist, although he does have a Doctorate of Education.
Being a member of a mental health professional association is a much better recommendation.
I personally would never go to a psychiatrist for two reasons:
one thing to remember… the majority of psychologists are not involved in either treating patients or even illness. Psychopathology and abnormal psychology (which deal with mental illness) are only 2 of the many fields of psychology. Psychology is primarily a research field, and like any other part of academia (history, chemistry, english lit, comparitive religion) there are LOTS of sub-divisions where people study. Psychology is no different than say chemistry with the range of applications and sub-subject matter.
Psychiatry, as has been mentioned, is a medical degree, focusing on the treatment of illness. Psychiatrists use medicine or therapy to accompish their goals, btu they are concerned more with treatment than research.
Jason R Remy
“No amount of legislation can solve America’s problems.”
– Jimmy Carter (1980)
Whatever, they are both more nuts than their patients…I wonder why that is?
Also, having seen many many of both of these types [it takes a long time when you can’t hear them and they have to write out stuff][plus, in my family you are treated as if you need them, even if you don’t] & when they start talking about themselves [unless you ask them a question about themselves], that is a sign to get a new shrink.