Berlin: It starts when the days get shorter in late autumn and often does not disappear until March: winter depression.
It not only causes sufferers long periods of feeling down, but also is accompanied by other aggravations such as restless sleep, loss of drive and a state of anxiety. Experts say one of the best ways of alleviating the problem is light therapy.
The problem occurs because when the days get shorter and there is less daylight, the body produces more melatonin, a hormone that causes drowsiness.
"A slightly depressed mood during the dark months of the year is nothing unusual," said Jürgen Zulley, a sleep therapist at the University of Regensburg in southeastern Germany.
As opposed to a normal feeling of melancholy, winter depression is characterised by an added need to sleep, ongoing lack of energy and strength, trouble concentrating and overall diminished vitality.
Malek Bajbouj, psychiatrist at Berlin's Charité university hospital, said a person is said to be suffering winter depression when the depressive state occurs every day, lasts two weeks or longer and when the episodes occur in at least two consecutive years.
Light therapy is the most practical solution, an expert says.
A special lamp is used to provide the sensation of bright sunlight. The therapy can take place at a doctor's office or at home. The lamp's white rays of light shine into the retina, stimulating areas of the brain, which in turn produce the hormone serotonin. A filter blocks out harmful UV rays.
The length of time spent looking at the lamp depends on its strength. Stronger light require just 30 minutes daily, while those with less strength require as much as two hours.
"The best time to use the light is in the morning so that the body recognises that the day has begun," said Bajbouj. Properly used, the lamp's bright light helps the inner clock regain its timing. The result is clearer thinking, better sleep and the ability to enjoy life to the fullest again.
Thomas Schluepfer, deputy director of the Clinic for Psychiatry and Psychology at the University Hospital in Bonn, recommends that people who suffer winter depression buy their own lamp.
"The whiter the light, the more effective it is," said Bajbouj, adding that taking a "light shower" in a solarium can improve someone's mood, but it does not have the hormonal effect of a prescribed light therapy. "Aside from that the UV rays in solarium light can damage the skin."
Basically, any natural light source can improve mood. Zulley also recommends moderate exercise in fresh air, preferably for an hour during midday when the sunlight is strongest. Even when it is cloudy, the sunlight is strong enough to make a difference, he added.