This is the VOA SpecialEnglish SCIENCE REPORT.

Some people feel sad or depressed during the winter months innorthern areas of the world. They may have trouble eating orsleeping. They suffer from a condition known as Seasonal AffectiveDisorder, or S-A-D.

Victims of S-A-D suffer its effects during the short, dark daysof winter. The problems are most severe in the months when there arefewer hours of daylight. When spring arrives, these signs disappearand S-A-D victims feel well again.

The National Mental Health Association reports that S-A-D canaffect anyone. The group says young people and women are at thehighest risk for the disorder. It says that an estimated twenty-fivepercent of the American population suffers from some form of S-A-D.About five percent suffer from a severe form of the disorder. Manypeople in other parts of the world also have the condition.

For example, some scientists who work in Antarctica suffer fromSeasonal Affective Disorder. During the long, dark winter monthsthere, workers have difficulty finding enough energy to do theirjobs.

The idea of health problems linked to a lack of light is not new.Scientists have discussed the issue since the beginning of medicine.More than two-thousand years ago, the Greek doctor Hippocrates notedthat the seasons affect human emotions.

Today, experts do not fully understand S-A-D. Yet they agree thatit is a very real disorder. Many doctors think that a change inbrain chemistry causes people to develop S-A-D. They say people withthe condition have too much of the hormone melatonin in theirbodies.

The pineal gland in the brain produces melatonin while we sleep.This hormone is believed to cause signs of depression. Melatonin isproduced at increased levels in the dark. So, its productionincreases when the days are shorter and darker.

To treat the disorder, victims of S-A-D do not need to wait untilspring. Experts know that placing affected individuals in brightlight each day eases the condition. There are other things peoplecan do to ease the problem. They can increase the sunlight in theirhomes and workplaces. They can spend more time outdoors in the freshair during the day.

One study found that walking for an hour in winter sunlight wasas effective as spending two-and-one-half hours under bright lightindoors.

This VOA Special English SCIENCE REPORT was written by GeorgeGrow.