One theory maintains that spring fever is caused not by warm weather but by increased daylight. The light is measured by the eyes and relayed to the brain's pineal gland, which responds by reducing its secretion of melatonin, a hormone that regulates the daily biological clock and controls mood and energy levels. As spring days get longer, the chemical starts to disappear and people become more energized. Sex drive, enthusiasm and confidence all increase. Conversely, as days get shorter in the winter, melatonin builds up.
People feel sluggish and lethargic and start to slow down.
Light, however, is just one factor. The fragrant aroma and soft winds of spring can trigger tremendous emotional responses, including euphoria and sadness, Fisher said. For schools, spring fever is one of the greatest challenges of the year. Not only is the weather a constant distraction, but the end of the school year is in sight. While any change affects behavior, some pediatricians and psychologists say they get more referrals for learning disabilities and attention deficit disorder than any other time of the year.