I always get depressed this time of year and my running suffers. Once spring comes and we get some nice days I feel normal and happy again. Unfortunately I live in place with long cold winters, so it can be pretty rough. Does anyone else experience this? Any ways to treat it?
Get your Vitamin D and Vitamin B levels checked. You are surely low in Vitamin D, maybe Vitamin B. The doc will tell you how much to supplement with based on where you're at. Low Vit D levels cause symptoms similar to depression -- depressed mood, low energy, lack of motivation, hypersomnia, amongst other things. Google it.
You can also get a special ultraviolet light and spend 15 min a day in front of it. But make sure it is designed for SAD, that the type of light is correct.
Good luck.
This oughta help: