More recently, our sunlight dependency has been studied and identified as a condition called Seasonal Affective Disorder, also known as SAD. SAD is type of depression, fluctuating with the seasons. Of course, not everyone is affected by this condition but SAD emphasizes just how very common lack of energy and loss of motivation is during the winter months.
Lethargy during the colder seasons appears to be linked to the amount of daylight we are exposed to. Indeed, in winter, the days shorten and many of us go to class or to work when the sun is not yet up and leave when it is already dark outside.
I know your first instinct when Spring arrived was to complain about the precious hour of sleep you lost as the clocks changed - but stop grumbling: the lost hour will be put to good use with one major positive perk: more sunlight! As the author, Hemingway, wrote in 1964, "When spring came, even the false spring, there were no problems except where to be happiest."
Sun has always been depicted as a source of joy and positivity. As it happens, this representation was rather accurate. American researchers at the National Institute for Mental Health (NIMH), recently found that natural light affects brain areas that regulate mood. Sunlight thus has a strong impact on both well-being and mental health. Levels of serotonin, a hormone associated the regulation of emotions and with happiness, increase when we are exposed to sunlight.