SAD light (I got mine from Lumie) and Vitamin D from Autumn to Spring. I find I'm better if I "go with the flow" - i.e. go to bed earlier and get up later (during mid winter I often sleep for 9-10 hours) and see it as a time of semi-hibernation, rather than fighting to maintain the same level of activity as in Spring and Summer. Make sure you get some daylight every day (as others have said). In the middle of winter, I often walk down to the postbox (if I've nothing-else on) to give myself some daylight, and when it's icy I've been known to just potter in my garden in the middle of winter swaddled in coat, gloves, scarf, hat, etc !