depression
"I switched from Prozac (which if anything made me feel more depressed) to Zoloft about a month ago and it has been FANTASTIC. 75mg a day, kicked in about 2 weeks, little to no side effects, more energy and generally just a massive relief. 

In my case, it's also caused a bit of weight loss (around 5 pounds) which is likely due to the medicine causing a loss of appetite and some diarrhea which is far from pleasant."