Most PWP will need to at least TRY an antidepressant as a result of depressed mood for at least more than two weeks. By this I mean that it takes something very major to put one in the "big ditch" of depression.
And it's all "brain chemistry changes that cause depression. Try to get through this.
http://mindboosters.libraryonhealth....4b3f&chapter=6

It's mostly a lot of biochemistry, which may not be what one needs to hear, but basically the human brain, like all organs , is in a delicate balance with it's environment. When levels of the "neurotransmitters" that are "command signals" for our mood, are either present in too little or too much of the "normal" concentrations, things happen that we can help but notice. Depression in PWP usually hits people like a freight train; people who have had stable levels of the various mood controlling neurotransmitters for years, all of a sudden find themselves thinking gloomy "depressive thoughts", and for no reason, find themselves crying over the drop of a pin. And this includes big strong men and big strong women, as well as those who went through their previous life with the will of George Patton, or the daily tension of a seasoned army doctor, who has done the most incredible things and never flinched, being reduced to a crying, blithering, non-functional self.
True depression has to be real as far as imbalances in neurotransmitters are concerned. A normal person can grieve over a close loved one, intensely for weeks, or longer, and then finding themselves all of a sudden "lifted out" of their down mood and "normalize" again. However, the presence of disease which permanently alters the delicate balance of neurotranmitter synthesis and concentrations in the brain is what triggers "major depression". Major depression varies from minor depression in that people often say that they "have never felt this way for so long , over something that is causing their horribly bad feelings, for such a long time. No amount of "talking it out" works well for major depression, because neurotrasmitter levels cannot "equalize themselves", and thus help in making the person feel better. For someone whom has never experienced major depression, quite frankly, they will "never understand it".
Well, one bad day about 3 years into PD; I felt it. 42 years old; beautiful wife and 3 kids; great job; everything to live for. PD had not yet "crippled my emotions. But then the dark cloud of depression hit; I felt like suicide was the only way "out". So I tried all they had, Prozac, Wellbutrin, Amitryptiline, and nothing worked until I found the rather new to the market "Effexor". THis was the right choice , insofar as it took care of the reuptake inhibition of not only Serotonin, but also weakly at dopamine receptors, but most importantly at Norepinephrine uptake sites (Norepinephrine is made in the brain from dopamine, already in short supply, and is a major mood regulator "neurotransmitter").
Now I do recommend Effexor as a relatively quick acting and very efficaceous,( especially in PWP) but it has it's warts too. These include an awful withdrawal syndrome, so you should either take it for life or go through a very slow down titration, if you later want to try going without it. And men, I think you'll have to ask for a script for Levitra, as it absolutely kills your libido.
Just remember, it is better to take a pill than go for a kill. Antidepressants work! The social "stigma" has almost dissappeared, but patient reluctance to continue the regimen when you are feeling better is rampant. Just like taking Dopa in an attempt to normalize your PD symptoms, because you simply do not have the correct biochemical pathways to make enough of your own dopamine anymore. Other biochemical pathways to other neurotransmitters go "errant" too; and their aren't too many ways yet known how to deal with the very difficult problems that this causes to our mood. Methinks 'nuff said.cs