Clinical depression can also be cyclical and triggered by events. Clinical depression can also be defused short term by events but in the long run always comes back.
I know this for a fact. Even lifestyle changes do not necessarily affect Clinical Depression. It seems to be a chemical imbalance. It took several tries with different drugs but I am doing quite well now.
Before Zoloft, even if everything in my life was really OK I was quite unhappy and depressed. I do believe that Zoloft has saved my life and I have experienced no side effects from it at all. I plan to take it every day for the rest of my natural life.
I (heart)my Zoloft and PremPro too. Keeps me sane.