Yeah, admittedly I'm normally one to say "sheesh, do we need another 'name' for people's depression? It's winter blues, we all deal with it", but there is a difference between general blah and feeling helpless. And, I also notice that some seasons have a higher risk of depression than others. Mine's actually worst as spring starts to break, I think it's actually winter finally piling up.
Also, I believe depression tends to be higher after the first of the year. With November/December, the season is there, but we're buoyed up or just kept busy by the holidays. When we slow down, it can all come down on us.