Fact or Fiction?; April 2008; Scientific American Magazine; by Christie Nicholson; 1 Page(s)

When the dark chill of winter gives way to the sunny warmth of spring, many people find themselves in the throes of spring fever: restless, energetic, romantic. Other symptoms, says Michael Terman--an expert on biorhythms at New York-Presbyterian Hospital--include increased heart rate, appetite loss and mood swings. Clearly, the condition is real, even if it is not, as Terman notes, "a definitive diagnostic category."

Researchers may lack an explanation of its biological underpinnings, but they do have a number of clues. Some evidence that the changing seasons affect human mood and behavior comes from Matthew Keller of the University of Colorado at Boulder. In a study of 500 individuals in the U.S. and Canada, he found that the more time people spend outside on a sunny spring day, the better their mood. Such good moods decrease during the hotter summer months, and there is an optimal temperature for them: 72 degrees Fahrenheit, otherwise known as room temperature.