Since the switch to wintertime, the night falls earlier and the sun is scarce. Some people feel they never see the light of day. The lack of natural light prevents the body from synthesizing vitamin D, which influences the mood. As a result, some people suffers from seasonal depression in autumn and winter. The symptoms resemble those of a “classic” depression, namely a lack of energy and motivation despite long nights of sleep, decreased libido, increased appetite and social isolation.