The term “spring fever” may conjure images of children bursting to get outside and play in the newly-pleasant weather, or even romantic couples swooning over each other. But the real spring fever is almost the exact opposite of those things, characterized by lack of energy and depressed mood. It’s not contagious, however. While there is medical debate about the causes of spring fever, the problem arises from how your body is adjusting to the change of season, rather than a virus. One possible cause, for example, is that, during the dark days of winter, your body has used up its reserves of serotonin, a hormone that promotes positive moods. As the days get longer and you get more exposure to sunlight, your body kicks into hormone production mode again, but that initial boom in production actually uses a lot of energy, leaving your body feeling temporarily sapped. Another theory is that rising temperatures case your blood vessels to expand, resulting in a drop in blood pressure. But whatever the cause, there is one certain cure: summer.