It CAN be caused by an unbalance, it can also be caused by a number of other things like lack of exercise and unhealthy food. Treat your body like you do your car, you don't put grease and oil in your gas tank, why put that shit in your mouth. Your body needs the correct fuel to run right just like your vehicle.
I was diagnosed with depression several years ago; mom died, divorce, home foreclosure, self esteem issues. I took Zoloft for a while and it really helped a lot. Getting outside, exercising, and eating right made me feel just as good.
I know it sounds lame, but the only reason I'm probably still alive after the downward spiral I had is my son. As a single father, he's the thing that keeps me going every single day regardless if I feel good or not.