Chicago Poets and painters have long been considered the experts on spring fever, the seasonal malady that can empty schools, boost restless energy and cause an unexpected rash of friendliness. But scientists say spring fever is more than just an emotion romanticized in song and verse: It's physiologically real.
Generally spotted in listless, lazing souls on warm, sunny days, spring fever is caused in part by daylight and the subsequent chemical changes that take place in the body, according to chronobiologists, who study the relationship involving a person's body clock, mood and behavior. Increasingly, scientists are finding that many biological and behavioral processes follow daily, monthly and yearly cycles.
"Like other animals, we have strong seasonal rhythms which are more pronounced in some people than others," said Charmane Eastman, director of the Biological Rhythms Research Laboratory at Rush-Presbyterian-St. Luke's Medical Center. "Some people get winter-depressive and hypomanic in spring and summer."
Marketers love spring because consumers are more likely to buy diet and fitness products, beauty treatments, car maintenance and home improvement items, according to a recent survey by American Demographics Magazine.
But there is a dark side to the season known for volatile weather swings. Spring is when insomnia, vehicle accidents and criminal activity increase.
And April is one of the months that has the greatest number of suicides, perhaps because people who have seasonal affective disorders have more energy.
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 pea-size 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.
The body clock which is generally not on a 24-hour schedule has a strong role in spring fever, according to Michael Smolensky, author of "The Body Clock Guide to Better Health."
"Light is mood-elevating. A lack of light has the opposite effect," he said. "Those who have seasonal affective disorder exhibit altered circadian rhythms in the body. When we see light, it helps to reorganize biological clocks that became misaligned during short, overcast time periods of winter months."