SAD

Seasonal Affective Disorder. (SAD)
It's when you are affected by the weather, mood-wise.
Its easy to see why... it looks bleak and un-green out of the window, temperatures do not promote outdoor living (unless you are a ski instructor).
Specifically, according to the Villanova University website,

http://www.villanova.edu/studentlife/counselingcenter/infosheets/psych_topics.htm?page=winter_blues.htm

* SAD has been linked to a biochemical imbalance brought on by the shortening of daylight hours and a lack of sunlight in winter
* Your mood is partly influenced by sunlight, melatonin, serotonin, and vitamin D (cholecalciferol)
o Melatonin (sleep hormone) decreases when it is light
o Serotonin (hormone associated with wakefulness and elevated mood) increases when it is light
o Vitamin D helps the body maintain ↑ levels of serotonin during the winter
o Light stimulates the production of cholecalciferol, which the body eventually transforms into vitamin D

So basically, you tend to hibernate against your will.

Let's look at some risk factors,

* Limited light exposure -YES
* Younger people and women -YES
* Distance from the equator -YES

* January and February – the most difficult months - YES
* Feeling let down after the holidays - HUH?