It's true that low seratonin levels can cause depression. I'm on disablility because of depression, and have been for almost 5 years. I have what is called "major, chronic, treatment resistant clinical depression". Whew, that's a mouthful! I have tried a dozen different drugs and drug combos, and even had electroconvulsive therapy a couple of years ago. It didn't help me, but it did fuck up my memory a lot.
I find that smoking bud actually helps with my depression....with my general mood anyway. I tend to think about my moods and emotions more clearly and actually have some insights that help me out when dealing with daily life.

Have a safe and joyful holiday everyone!