There is a hormone linked to mood and wellbeing called serotonin. Sunlight encourages the body to produce it and its levels drop when time spent in the sun is reduced.
9. You feel blue
In recent studies, results showed that people with a little amount of vitamin D were more likely to be depressed than those who had ample doses. Studies also connect low vitamin D levels in the blood with other mood disorders aside from depression. It is also link to premenstrual syndrome and seasonal affective disorder.