A lot of people don't believe in this, but I have known enough people who suffer from it to know it's real. SAD, or Seasonal Affective Disorder is a type of depression related to changes in season. In Northern Michigan we lack sun in the winter and it can definitely affect a person's mind and attitude.
If you're feeling a little "dumpy" this time of the year, don't have as much energy, or your outlook is just not as bright as it normally is, you may be suffering from SAD. I definitely feel it and I think my mom does too. To combat it I bought us each a Salt Lamp, which is supposed to be a type of light therapy for SAD.
SAD can also be worse for someone who suffers from depression, or has a family history of depression or bipolar disorder. If you're struggling this time of the year and aren't sure why, check out this article
and get the facts on SAD.