I think Seasonal Affective Disorder (SAD) should win the prize for most appropriate acronym, since folks suffering from the disorder feel well...more than a little sad. About 1 in 5 Americans suffer from this well known but rarely treated disorder, that leaves people feeling a decrease in energy and cheerfulness, as well as a decline in productivity and creativity.
The lack of light that accompanies the winter months disrupts natural sleep / wake cycles creating effects similar to an extreme case of jet lag. Instead of recovering in a few days, it can take upwards of 5 months.
SAD is not treated with antidepressants, since those suffering from it are not emotionally depressed. It is more like they are worn down like an over used battery so light therapy is generally prescribed to recharge them. Patients sit in front of a really bright light (10,000 lux) every morning for 45 minutes to 2 hours. These lights are available to the public through the Center for Environmental Therapeutics , for about $200.
Another option is to plan a vacation to a very bright, very warm destination. Hello Tahiti!!!