Maybe the best way to cure depression would be to take pills that make you feel really, really bad, then stop taking them...
(Note that I haven't advised taking antidepressants and then suddenly stopping them, but rather the opposite of that - suddenly stopping antidepressants is known to be dangerous.)
Somewhat similar methods have been used on Anxiety, a closely allied disorder, and there are other reasons to suppose such an approach might work. And I can offer one personal experience that might provide anecdotal evidence for this treatment for depression.
Years ago, suffering from chronic pain, I experienced depression from time to time. The last time that it was acute, a few years ago, I was given a rather new combination anti-depressant to try. Ultimately, the prescription worked well, although in a perverse way. Rather than having little initial effect and then raising my mood, after only a day or two my mood began to plummet. In a few weeks I was remarkably more depressed than I had been when I started - so black, and increasing, that when I was certain I had been taking the pills long enough to get the full result, and was still plummetting, I quit. Wham. As the pills wore off, my mood shot up, quickly to where it was when I began taking the drug, and then on up to normal. Maybe, in seraching for cures for depression, we should be looking for drugs that have strong mood-lowering effects.
Now to chronicle some of the evidence and experiments that have already been done on the closely allied symptom of Anxiety, including General Anxiety Disorder:
We know that treating GAD (General Anxiety Disorder) with, say, valium or other benzodiazepam class drugs actually makes the illness worse in the long run. You become more anxious because you've become used to pills that make you less anxious - this is at least part of the explanation as to why benzodiazepam medications are so extraordinarily addictive. This might suggest that deliberately increasing ones levels of anxieties might, conversely, increase one's tolerance, and decrease anxiety over time.
We also know that the anxiety associated with phobias can be very effectively treated by increasing, graduated exposure to whatever the patient is phobic of - even exposure to heights or spiders in a virtual environment can help treat such phobias. This form of treatment is now very well established.
All of which might help explain why David H. Barlow of the Center for Anxiety and Related Disorders at Boston University is using "The Cruelest Cure", increasing patients anxieties in order to treat them. This work is described in New York Times Magazine article, "The Cruelest Cure" By Lauren Slater, November 2, 2003: http://www.nytimes.com/2003/11/02/magazine/02FEAR.html?pagewanted=1
Perhaps the next step is to look at depression in the same way, and find out whether mood dampeners work better in the long run when treating depression. (They might get faster and stronger results, too.) Of course, this has to be done with some supervision - suicide is a risk that has to be taken seriously, although often patients will kill themselves as their mood, energy, and decisiveness improves, so it may turn out that this is a smaller risk than one would suppose. Or, such therapy might turn out to be useful only with patients so seriously ill that they are already closely supervised.
There is a "do it yourself" version of this therapy for depression which I have tried and with considerable long-term success, although I would warn that it may not be risk-free, either. When you are depressed, try to experience as fully as possible, the dark feelings, and to draw them out. Pay attention to subtile body feelings to do this. At the same time, do experiments to convince yourself that these feelings, however intense, are nonetheless free-floating - a key sign that your feelings are not only "reactive" or firmly based in reality, but simply irrational brain-weather. If you experience anxiety, self-denigration or guilt, for example, find a memory of a past action or experience of yours that is a very small or ridiculous fault. Deluged by guilt feelings, I used a silly example of littering - when I was sixteen, I had wanted to get rid of a candy wrapper but didn't want to litter, exactly - so I stuffed the wrapper inside some litter that was already in the street. If, as you think about this memory - even a made-up or false memory if you have a good imagination (borrow my example) - and repeatedly return your attention to it, the intense feelings shift so that they now seem to be "about" this triviality, you'll know that the feelings shouldn't be taken too very seriously. When I kept thinking about my having stuffed one piece of litter into another, sure enough the intense guilt I was feeling about more serious matters transferred easily enough onto this obviously less than catastrophic event in my life. After that, the going was much easier. Suicide is often a consequence of extremely intense guilt feelings which are taken at face value by the sufferer; when a quick thought experiment as described can convince the depressed patient that their thoughts and feelings shouldn't and can't be taken literally, and therefore require no action, much less ending their life. That those feelings are really about those feelings, and nothing else.
Now, I said that this do it yourself method wasn't risk free, and I should repeat that this method may well very sharply increase the bad feelings. There are other symptoms to worry about as well, such as, most frequently, dizziness - and some recent studies have tied suddenly ceasing anti-depressants, particularly accidentally, to an increased risk of suicide. For a good summary of the risks, see The New York Times article "How to Stop Depression Medications: Very Slowly" by Mary Duenwald, May 25, 2004, at http://nytimes.com/2004/05/25/health/psychology/25cons.html
While these risks are a good argument for caution and supervision, it is nonetheless worth remembering that feelings of anxiety, guilt or sadness won't kill you themselves, and by willingly experiencing them you may gain the reassurance that your feelings are very much exaggerated at times, rather than made necessary by any facts out there in the world, as it were. You may also notice that you start doing more, if depression has been restricting your activities due to a fear (concious or unconcious) on your part that lousy feelings may be triggered that you won't be able to deal with - one rather negative way some people deal with depression.
Arguably, meditation offers a similar but better solution, in that it allows one to gradually expand one's awareness of one's body-feelings and emotional feelings (if those can be distinguished) but very gradually, one small bite at a time, and therefore, more safely, over years.
Against this proposal, research seems to suggest that drugs such as Prozac change the brain in ways that increase its sensitivity to Serotonin (good for mood, since Prozac is a serotonin reuptake inhibitor that increases the amount of Serotonin in the brain by slowing or inhibiting its removal). Which suggests that these drugs may be working themselves out of a job, and that mood lowering drugs should be carefully examined to make sure they aren't lowering sensitivity to Serotonin. Doubtless, the true picture of depression is complex.