Seasonal Affective Disorder (SAD) 
The Fall and Winter are characterized by ever-decreasing amounts of sunlight in the more northerly latitudes. Overcast days in Fall and Winter have a larger than usual impact on our loss of total sunlight.
Some people are especially affected by the lack of natural sunlight that occurs this time of year. Like annual rhythms in other animals, humans can be influenced by the duration and intensity of sunshine. As exposure to sunlight, fresh air and exercise dwindle to very little, some people become more irritable or lethargic, others lose the vitality needed to study and socialize or to do anything fun or interesting.
We have coined the term "Seasonal Affective Disorder," SAD, to describe someone who becomes significantly depressed at this time of year due to lack of sunlight.
For anyone affected, these actions might help:
- get outside as much as possible and soak up the sun!
- exercise (walking, running, skating, skiing..) and fresh air are almost always beneficial
- spend time in full spectrum lighting (which comes close to replacing sunlight)
For info on Health Service's light therapy services, click here:
http://www.unh.edu/health-services/ohep/sad-lighttherapy_light.html