Science: The story of the blues

The inhabitants of Helsinki were still depressed but relieved that the snow had come at last. Their winter has short dark days, and the rain had increased the gloom. It is the arrival of snow that lightens everything up bringing some cheer. Later on it will even be possible to ski to work. The newspapers reported that winter depression was widespread and that one third of teachers and scientists were showing signs of SAD: Seasonal Affective Disorder, the winter blues that are the result of the lack of sunlight. My host had installed sun- like lamps in her laboratories and the results were encouraging - people were talking more. The fashionable Cafe Engel in the centre of town had also installed sun lamps next to tables by the windows.

One might have thought that SAD would occur much more in Finland than elsewhere in Europe, but this is not the case. Local psychiatrists assured me that the incidence of SAD was more or less the same throughout Europe, running at about one to two per cent of the population, and this included countries like Spain and Italy. However, there was a difference in the severity of the disorder. Women are found in most studies to be much more vulnerable to SAD than men, the incidence sometimes being five to 10 times higher.

Seasonal depression was recognised as long ago as 400BC by Hippocrates and there is evidence that Greek and Roman physicians treated this sort of melancholy by directing sunlight at the eyes. In more recent times a doctor accompanying an Arctic expedition at the end of the last century noted the profound influence of the absence of light on both the Eskimos they visited as well as the members of the expedition. He described the syndrome as involving fatigue, lack of sexual desire and a generally depressed mood. He used bright artificial light to combat their sadness.

Some of the features that distinguish SAD from more classical depression are an increase in sleep and an increase in both appetite and weight. There is a craving for carbohydrate-rich foods. And unlike depression, the episodes are typically resolve by springtime, though for some individuals it continues into the summer. The condition can also occur in children who show irritability and can have problems at school.

Surprisingly, there was little systematic investigation of the condition until the 1980s, though a German psychiatrist had described an engineer whose annual seasonal depression responded well to treatment with a sunlamp. And this treatment has been shown to work in a number of clinical trials. However, it has not been easy to control for the placebo effect. Morning seems to be the most effective time for treatment and a 30 minute session works well. The eyes mediate the effect of the light, but in one case a blind sufferer responded positively. Unlike drugs there are no reports of side effects on normal subjects exposed to the light regime.

There is also what is known as summer SAD, but it is not as common nor well researched as its winter companion. Changes in environment have not been established as a satisfactory treatment, but patients do respond to anti-depressant drugs. What causes the winter blues? One hypothesis links the condition to melatonin which, as jet-setters know all too well, is high at night and can control our daily rhythms. The idea is that light reduces the amount of melatonin the brain produces, and high melatonin is associated with depression. There is also the suggestion that there is a reduction in serotonin levels. Serotonin is a chemical that acts as a signal between nerves and low levels are implicated in depression - Prozac is supposed to work by raising serotonin levels.

So as winter progresses we hypochondriacs can plead SAD as the cause of our inability to rise in the morning as well as our irritability. Those who live with us should be suspicious but not dismiss it out of hand.