Prozac was approved by the FDA
based on carefully manipulated data from a number of clinical trials.
Eli Lilly, the company that developed and marketed Prozac, recombined results, dropped participants due to adverse reactions, removed placebo users because they improved on the placebo, and basically twisted the scientific method into a pretzel to get the drug approved. In the end, only 17 studies using three protocols (or 1,730 patients) were deemed scientifically adequate by the FDA, and only 286 out of those 1,730 patients were given Prozac. The rest were given a placebo or an older, proven antidepressant.
Of those 286 patients, only 63 were on Prozac for a period of more than two years. At least one of these 286 was accidentally given both Prozac and the older antidepressant, Tofranil.
In the end, the drug was approved despite being repeatedly shown (in the unsubmitted data) to be inferior to the previous antidepressant, and in many studies, inferior to a placebo!
So, if you want to take a drug to improve your mood, I suggest sugar pills. Proven (in 70% of cases) to improve your mood.
Source for data: Talking back to Prozac, Peter R. Breggin, MD, (c) 1994; his data came from FDA reports. I strongly recommend this book for anyone who is taking, might soon be taking, or has ever taken Prozac.