This condition, know as Seasonal Affective Disorder (S.A.D.) is especially common among those who dwell in northern climates, where winters (and the attendant darkness) come sooner and last longer.

"It's tempting to say that it's symbolic. That is, that the end of the year, with its connotations of finality and death, stirs in people a sense of despair and impending doom," writes Dr. Belter in the New England Journal of Mental Derangement. "In fact, the condition-- like many emotional disturbances--is of a chemical nature. Darkness discourages the body's natural manufacture of serotonin, an enzyme in the brain that stimulates feelings of wellbeing. Whereas light--natural or artificial--spurs the creation and circulation of serotonin within the brain."

"Thus, you see, the negative effects of S.A.D. can be actively countered by regular exposure to a light source. Even on overcast, sunless days, a half hour or so of exposure to a properly bright lamp can change a person's whole mood."

Belter further explains that S.A.D. is not a condition to be treated lightly, as it can--and has--led many of its sufferers to suicide due to deep depression.