Last week of February is the harshest of winter. As other anons mentioned get D3 through supplement or get some sunlight in your eyeballs. I've tried anti-depressant on and off for a few years (off them now) but notice that St. John's Wort has the same effect but the holistic alternative. Feels like I'm on low-dose acid after a week (vibrant colors). Worst part of depression is the loss of perception of color, literally everything gets dull.
We've been relying on dried herbs through Winter for a while I'd imagine. It has just been driven out of tradition because of petro-pharma.