Many of people have noticed (at least on the northern east coast) that at 4 pm the sun is already setting and it is dark outside, and by 5 p.m. it is nearly pitch black. With this time of the year brings sadness, and also brings Seasonal Affective Disorder (SAD). Many people are stricken with this during the months where the sun is not present.
USA Today reports that over 14 million people have SAD. The darkness of the day increases melatonin, which is a hormone produced in the brain that tells the body when to sleep and wake up:
“Doctors aren’t sure of the exact cause but believe it’s triggered by dwindling daylight as winter approaches. Darkness may disrupt the body’s internal “clock” by increasing melatonin, a hormone produced in the brain that tells the body when to sleep and wake up. Lack of sunlight may also lower levels of serotonin , a brain chemical that controls mood, experts said.”
Some ways to combat this can include special lamps and light boxes that give off brightness that is thought to be soothing and act like the sun. There’s also depression medication and psychotherapy that can be done, because SAD really is a form of depression and can be treated as such.
Zennie Abraham 
Bill Carroll