When spring is in the air and there is more natural light, people (and animals) go out more, are more happy and more active. But the opposite also applies.
A deprivation of light causes a change in mood, as can be witnessed when the long dark winter nights arrive. People get more irritated or depressed, they have less resistance and thus have a bigger chance of becoming sick. Even so sick, that there is a statistical higher suicide-rate in the Scandinavian countries when at wintertime, when at daytime, there is no light at all!

This association between light deprivation and depression is well established. A study in the Proceedings of the National Academy of Sciences now has scientific results to prove that light deprivation causes in the brain.

Neuroscientists kept rats in the dark for six weeks. In this time, the animals not only exhibited depressive behavior but also suffered damage in brain regions known to be underactive in humans during depression. The researchers observed neurons dying that produce norepi­nephrine, dopamine and serotonin — common neurotransmitters involved in emotion, pleasure and cognition. This neuronal death, which was sometimes also accompanied in some areas by compromised synaptic connections, may be the mechanism underlying the darkness-related disorder.