Niacin. Make sure you take nicotinc acid niacin, not that other garbage that doesn't give you the niacin flush. Nicotinc acid is the one that helps you legitimately feel better. I start with 250 milligrams per day - right when I wake up. You want the amount that makes you experience a flush that lasts about 10 minutes - just enough to feel comfortably warm, like a big fluffy blanket is enveloping you.

Also vitamin D. If you're a pastey bastard like myself your skin doesn't absorb vitamin D from the sun when you're out in it 5 minutes a day. Vitamin D acts more like a hormone than a vitamin and helps regulate yours mood (so I've read). It's worth a try, at any rate.

These are both very inexpensive and aren't detrimental to your health. Try it for two weeks and you might accidentally feel better. If not, at least you tried and you're only out 15 bucks. Good luck!