The weather is getting warmer and the days longer, the first buds are sprouting and birds are back to chirping in the morning. Not everyone enjoys spring, though. Some people suffer from spring fever, whose symptoms include circulatory problems, lethargy and tiredness. For them, the switch to summertime is especially upsetting.

But there are two pieces of good news for those who lack a spring in their step when winter wanes. First, there are ways for people to recharge their batteries. Second, spring fever symptoms disappear by the end of April.

"By May, a balance has been reestablished," says Thomas Weiss, a general practitioner and psychotherapist in the German city of Mannheim.

Spring fever is a sign that the body is acclimating to the new conditions, namely more ultraviolet (UV) radiation and warmth. Ill and elderly people have the greatest problems in adapting. And more women are affected than men, Weiss says.

The increased sunlight upsets the body's hormonal balance. "More serotonin is produced because of the UV rays," explains Michael Schellberg, a psychologist in Hamburg.

Serotonin is known as the "happiness hormone". But it takes a while until serotonin has gained the upper hand over the hormone melatonin, which causes drowsiness. The body produces melatonin in greater amounts in the dark months of winter. The "struggle" between serotonin and melatonin exhausts the body.

Blood vessels also adjust to the warm season by expanding. Blood pressure drops and people become tired.

"A lot of bacteria become active in spring temperatures," remarks Schellberg, noting another possible cause of fatigue. People often do not notice that they have an infection. Their bodies defend themselves without clear signs of illness, but they feel run-down.

The time switch in late March makes springtime even more difficult for sensitive people. Losing an hour can knock them off their stride for days or even weeks because every healthy person has a biological clock.

"It's situated on the lower floor of the brain - in the hypothalamus, to be precise," says Horst-Werner Korf, director of the Senckenberg Chronomedical Institute in Frankfurt. The hypothalamus is the seat of the autonomic nervous system -also known as the vegetative nervous system - and is responsible for such things as maintaining blood pressure, controlling body weight and appetite, and regulating sleep and arousal.

People are not at the mercy of the body's adaptive inadequacies, however. To fight spring fatigue, Weiss recommends exercise, contrast showers, sauna sessions and stepping outside briefly without a jacket now and then during the cool months, for example to go to the mailbox.

"This boosts the body's adaptability," he says, adding that no one would catch a cold from such a short outing into the cold. As regards saunas, he says it does not matter how hot they are. "What's important is that cold comes afterwards," he says. Taking a lukewarm shower after a sauna session has no beneficial effect.

The mind also plays an important role in spring fever, so having the right attitude helps.

"Some people don't really feel up to spring with all its activities," Schellberg says. They have made themselves comfortable during the winter months, perhaps with food high in calories. In spring, life becomes lively again. Though it is time to get off the sofa, some people prefer to prolong their winter hibernation and find an excuse for it in spring fever.

There is no problem with that. After all, experts say, by May at the latest everyone has overcome the seasonal lethargy.

"Then, like it or not, people start feeling frisky," Schellberg remarks. But until then, he says, outdoor exercise and light meals can ease the transition.

German Press Agency