Sleeping in Rooms With Even a Little Light Can Increase Risk of Depression, Study Finds

The reason behind this link is unclear, but the researchers believe it might be to do with the human circadian rhythm, the 24-hour cycle that tells us when to sleepand wake up, among other things, that is “programmed” by environmental factors. In the case of humans and many other creatures, light influences how much of the sleep-inducing hormone melatonin is pumped into our bodies, meaning we feel awake when the Sun rises and get sleepy when the Sun sets.

Source: iflscience.com