The first day of real spring in the cities of the north, after months of frozen slush and darkness, has an unofficial name among the less respectable. In Gothenburg when I lived there it was known as Tit Day: the morning when the public transport system was transformed as all the girls went to work in T-shirts.
This was perhaps rather vulgar but it was also a vivid expression of real deliverance from the draughty dark cellar of winter. SAD (Seasonal Affective Disorder) is now a recognised disease, striking almost everyone to a greater or lesser degree in winter; and the long grey winter we have just been through in this country has been one of the worst for it on record.
This January was apparently the most light-starved since records began, preceded by the tenth coldest December this century and the chilliest February for two decades. All of which has a demoralising impact on the human psyche. The weather produced record levels of winter depression.
"There might be a physiological explanation for it," says Cary Cooper, Professor of Occupational Psychology at the University of Manchester Institute of Science and Technology. "But I think it is probably more psychological in most cases, though some people do get it very badly."
Arctic countries have long had terms for the cafard of winter: "Cabin fever" and "Lapp sickness" both describe a sort of madness of distilled boredom which comes over people after months in semi-darkness with nothing to do outside. They also, have a special term for the grey season of transition between winter and spring, when the snow has receded in patches, leaving gashes of raw, frozen mud all over the lifeless earth and the icicles drip inexhaustibly without ever melting. That season of transition is when the suicide rate really perks up.
In more temperate regions, like southern England, there are likely to be less dramatic explanations for madness than the weather. Work, for instance. "The high-risk sad period, from October to March, is probably the time of year when people's workload is highest," according to Professor Cooper. "People are working longer and longer hours, getting up in the dark, going to work in the dark; and there are all sorts of reasons why it might make people feel depressed." And now that two-thirds of all couples are both working, the impact is heightened .
It has been a vintage year for SAD on the other side of the Atlantic. On the east coast, around New York, even if everyone there is always ready to seize on the latest neurosis, they have also had a particularly long and unremitting season of transition this year.
The insight from America, however, is that this can often be cured by moving northwards rather than south. There may be a physiological explanation for part of this, says Professor Cooper. Most of Canada is bright with snow at the moment, and the physiological theory of SAD claims that it is the lack of light which depresses susceptible people. Hence it can be treated by putting sufferers in special treatment cabinets and blasting them with artificial light made up to the frequencies of a delicious summer.
However simpler and more mundane cures may work, too. "There are other ways than going to Canada," says Professor Cooper. "Perhaps the simplest solution is to ensure that you go somewhere that there is a lot of sun." Those people with serious physiological SAD might need several two week- long breaks during the danger period.
Any expert who prescribes winter breaks in the sun must know what he is talking about. But Professor Cooper's advice can be even more helpful than that: "I think it's about changing your lifestyle," he says. For those SAD sufferers whose condition is less acute, "it might be enough to get away for a long weekend to a nice hotel." Change is all most of us need to escape from a dull, humdrum, overloaded world, full of black skies.
If none of these methods work, then Professor Cooper, originally from Los Angeles, has an ultimate solution: send people from here to experience the changeless all-year-round summer smog of his hometown. Then they will be thankful for an English winter. It is either that or wait for the T- shirts.
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