By Linda Geddes|BBCNEWS
The inhabitants of Rjukan in southern Norway have a complex relationship with the Sun. “More than other places I’ve lived, they like to talk about the Sun: when it’s coming back, if it’s a long time since they’ve seen the Sun,” says artist Martin Andersen. “They’re a little obsessed with it.” Possibly, he speculates, it’s because for approximately half the year, you can see the sunlight shining high up on the north wall of the valley: “It is very close, but you can’t touch it,” he says. As autumn wears on, the light moves higher up the wall each day, like a calendar marking off the dates to the winter solstice. And then as January, February and March progress, the sunlight slowly starts to inch its way back down again.
Rjukan was built between 1905 and 1916, after an entrepreneur called Sam Eyde bought the local waterfall (known as the smoking waterfall) and constructed a hydroelectric power plant there. Factories producing artificial fertiliser followed. But the managers of these factories worried that their staff weren’t getting enough Sun – and eventually they constructed a cable car in order to give them access to it.
When Martin moved to Rjukan in August 2002, he was simply looking for a temporary place to settle with his young family that was close to his parents’ house and where he could earn some money. He was drawn to the three-dimensionality of the place: a town of 3,000, in the cleft between two towering mountains – the first seriously high ground you reach as you travel west of Oslo.
I felt it very physically; I didn’t want to be in the shade – Martin Andersen
But the departing Sun left Martin feeling gloomy and lethargic. It still rose and set each day, and provided some daylight – unlike in the far north of Norway, where it is dark for months at a time – but the Sun never climbed high enough for the people of Rjukan to actually see it or feel its warming rays directly on their skin.
As summer turned to autumn, Martin found himself pushing his two-year-old daughter’s buggy further and further down the valley each day, chasing the vanishing sunlight. “I felt it very physically; I didn’t want to be in the shade,” says Martin, who runs a vintage shop in Rjukan town centre. If only someone could find a way of reflecting some sunlight down into the town, he thought. Most people living at temperate latitudes will be familiar with Martin’s sense of dismay at autumn’s dwindling light. Few would have been driven to build giant mirrors above their town to fix it.
What is it about the flat, gloomy greyness of winter that seems to penetrate our skin and dampen our spirits, at least at higher latitudes? The idea that our physical and mental health varies with the seasons and sunlight goes back a long way. The Yellow Emperor’s Classic of Medicine, a treatise on health and disease that’s estimated to have been written in around 300 BCE, describes how the seasons affect all living things. It suggests that during winter – a time of conservation and storage – one should “retire early and get up with the sunrise… Desires and mental activity should be kept quiet and subdued, as if keeping a happy secret.” And in his Treatise on Insanity, published in 1806, the French physician Philippe Pinel noted a mental deterioration in some of his psychiatric patients “when the cold weather of December and January set in”.
Why should darker months trigger this tiredness and low mood in so many people?
Today, this mild form of malaise is often called the winter blues. And for a minority of people who suffer from seasonal affective disorder (SAD), winter is quite literally depressing. First described in the 1980s, the syndrome is characterised by recurrent depressions that occur annually at the same time each year.
Even healthy people who have no seasonal problems seem to experience this low-amplitude change over the year, with worse mood and energy during autumn and winter and an improvement in spring and summer.
Why should darker months trigger this tiredness and low mood in so many people? There are several theories, none of them definitive, but most relate to the circadian clock. One idea is that some people’s eyes are less sensitive to light, so once light levels fall below a certain threshold, they struggle to synchronise their circadian clock with the outside world. Another is that some people produce more of a hormone called melatonin during winter than in summer.
However, the leading theory is the ‘phase-shift hypothesis’: the idea that shortened days cause the timing of our circadian rhythms to fall out of sync with the actual time of day, because of a delay in therelease of melatonin. Levels of this hormone usually rise at night in response to darkness, helping us to feel sleepy, and are suppressed by the bright light of morning. “If someone’s biological clock is running slow and that melatonin rhythm hasn’t fallen, then their clock is telling them to keep on sleeping even though their alarm may be going off and life is demanding that they wake up,” says Kelly Rohan, a professor of psychology at the University of Vermont. Precisely why this should trigger feelings of depression is still unclear. One idea is that this tiredness could then have unhealthy knock-on effects. If you’re having negative thoughts about how tired you are, this could trigger a sad mood, loss of interest in food, and other symptoms that could cascade on top of that.
However, recent insights into how birds and small mammals respond to changes in day length have prompted an alternative explanation. According to Daniel Kripke, an emeritus professor of psychiatry at the University of California, San Diego, when melatonin strikes a region of the brain called the hypothalamus, this alters the synthesis of another hormone – active thyroid hormone – that regulates all sorts of behaviours and bodily processes.
When dawn comes later in the winter, the end of melatonin secretion drifts later, says Kripke. From animal studies, it appears that high melatonin levels just after the time an animal wakes up strongly suppress the making of active thyroid hormone – and lowering thyroid levels in the brain can cause changes in mood, appetite and energy. For instance, thyroid hormone is known to influence serotonin, a neurotransmitter that regulates mood. Several studies have shown that levels of brain serotonin in humans are at their lowest in the winter and highest in the summer.
It’s possible that many of these mechanisms are at work, even if the precise relationships haven’t been fully teased apart yet. But regardless of what causes winter depression, bright light – particularly when delivered in the early morning – seems to reverse the symptoms.
It was a bookkeeper called Oscar Kittilsen who first came up with the idea of erecting large rotatable mirrors on the northern side of the valley above Rjukan, where they would be able to “first collect the sunlight and then spread it like a headlamp beam over the town and its merry inhabitants”.
A month later, on 28 November 1913, a newspaper story described Sam Eyde pushing the same idea, although it was another hundred years before it was realised. Instead, in 1928, Norsk Hydro erected a cable car as a gift to the townspeople, so that they could get high enough to soak up some sunlight in winter. Instead of bringing the Sun to the people, the people would be brought to the sunshine.
Martin Andersen didn’t know all of this. But after receiving a small grant from the local council to develop the idea, he learned about this history and started to develop some concrete plans. These involved a heliostat: a mirror mounted in such a way that it turns to keep track of the Sun while continually reflecting its light down towards a set target – in this case, Rjukan town square.
The three mirrors stand proud upon the mountainside
The three mirrors, each measuring 17 sq m, stand proud upon the mountainside above the town. In January, the Sun is only high enough to bring light to the square for two hours per day, from midday until 2pm, but the beam produced by the mirrors is golden and welcoming. Stepping into the sunlight after hours in permanent shade, I become aware of just how much it shapes our perception of the world. Suddenly, things seem more three-dimensional; I feel transformed into one of those ‘merry inhabitants’ that Kittilsen imagined. When I leave the sunlight, Rjukan feels a flatter, greyer place.
Not everyone in Rjukan has welcomed the Sun mirrors with open arms. Many of the locals I spoke to dismissed them as a tourist gimmick – though all admitted they were good for business. On the day I visited, the town was blessed with clear blue skies and a golden shaft of light descending from the mirrors, yet few people lingered in the town square. In fact, of the people I spoke to, it was recent immigrants to Rjukan who seemed most appreciative of the mirrors.
Andersen admits to having got used to the lack of sunlight over time. “I don’t find it so bad anymore,” he says. It’s as though the people who’ve been brought up in this uniquely shady place, or who have chosen to stay, have grown immune to the normal thirst for sunlight.
This is certainly the case in another Norwegian settlement: Tromso. One of the world’s most northerly cities, it is some 400km north of the Arctic Circle. Winter in Tromso is dark – the Sun doesn’t even rise above the horizon between 21 November and 21 January. Yet strangely, despite its high latitude, studies have found no difference between rates of mental distress in winter and summer.
One suggestion is that this apparent resistance to winter depression is genetic. Iceland similarly seems to buck the trend for SAD: it has a reported prevalence of 3.8%, which is lower than that of many countries farther south. And among Canadians of Icelandic descent living in the Canadian province Manitoba, the prevalence of SAD is approximately half that of non-Icelandic Canadians living in the same place.
Some people have an apparent resistance to winter depression – why?
However, an alternative explanation for this apparent resilience in the face of darkness is culture. “To put it brutally and brief: it seems like there are two sorts of people who come up here,” says Joar Vitterso, a happiness researcher at the University of Tromso. “One group tries to get another kind of work back down south as soon as possible; the other group remains.”
Ane-Marie Hektoen grew up in Lillehammer in southern Norway, but moved to Tromso 33 years ago with her husband, who grew up in the north. “At first I found the darkness very depressing; I was unprepared for it, and after a few years I needed to get a light box in order to overcome some of the difficulties,” she says. “But over time, I have changed my attitude to the dark period. People living here see it as a cosy time. In the south the winter is something that you have to plough through, but up here people appreciate the very different kind of light you get at this time of year.”
Stepping into Hektoen’s house is like being transported into a fairy-tale version of winter. There are few overhead lights, and those that do exist drip with crystals, which bounce the light around. The breakfast table is set with candles, and the interior is furnished in pastel pinks, blues and white, echoing the soft colours of the snow and the winter sky outside. It is the epitome of kos or koselig – the Norwegian version of hygge, the Danish feeling of warmth and cosiness.
The period between 21 November and 21 January in Tromso is known as the polar night, or dark period, but for at least several hours a day it isn’t strictly speaking dark, but more of a soft twilight. Even when true darkness does descend, people stay active. One afternoon I hire a pair of cross-country skis and set off down one of the street-lit tracks that criss-cross the edge of the city. Despite the darkness, I encounter people taking dogs for walks on skis, a man running with a head torch, and countless children having fun on sledges. I stop at a park and marvel at a children’s playground lit up by floodlights. “Do children climb here in winter?” I ask a young woman, who is struggling to pull on a pair of ice skates. “Of course,” she answers. “It’s why we have floodlights. If we didn’t, we’d never get anything done.”
It sounds dismissively simple, but a more positive attitude really might help to ward off the winter blues
During 2014-15, a psychologist from Stanford University called Kari Leibowitz spent 10 months in Tromso trying to figure out how people cope during the cold, dark winters. Together with Vitterso, she devised a ‘winter mindset questionnaire’ to assess people’s attitudes to winter in Tromso, the Svalbard archipelago and the Oslo area. The farther north they went, the more positive people’s mindsets towards winter were, she tells me. “In the south, people didn’t like winter nearly as much. But across the board, liking winter was associated with greater life satisfaction and being willing to undertake challenges that lead to greater personal growth.”
It sounds dismissively simple, but adopting a more positive attitude really might help to ward off the winter blues. Kelly Rohan recently published a clinical trial comparing cognitive behavioural therapy (CBT) to light therapy in the treatment of SAD, and found them comparable during the first year of treatment. CBT involves learning to identify patterns and errors in one’s way of thinking and challenging them. In the case of SAD, that could be rephrasing thoughts such as ‘I hate winter’ to ‘I prefer summer to winter’, or ‘I can’t do anything in winter’ to ‘It’s harder for me to do things in winter, but if I plan and put in effort I can’.
It also involves finding activities that a person is willing to do in winter, to pull them out of hibernation mode. “I don’t argue that there isn’t a strong physiological component to seasonal depression, which is tied to the light-dark cycle,” says Rohan. “But I do argue that the person has some control over how they respond to and cope with that. You can change your thinking and behaviour to feel a bit better at this time of year.”
This is an edited version of an article first published by Wellcome on Mosaic and is republished here under a Creative Commons licence. Visit Mosaic to read the longer version, which also describes how artificial light can regulate mood.
为什么冬天这种萧瑟暗淡的灰色似乎会滲透到我们的皮肤里并压抑我们的精神（至少在纬度较高的地区是这样）？很早以前，人们就发现了我们的身心健康会随着季节和阳光的变化而变化。《黄帝内经》(The Yellow Emperor’s Classic of Medicin)就描述了季节是如何影响所有生物的。这本关于健康和疾病的专著大约写于公元前300年。这本书指出，”冬三月，此谓闭藏……早卧晚起，必待日光，使志若伏若匿”（冬天是休养生息的季节……人应该随着太阳的起落早睡晚起，注意抑制欲望，避免情绪起伏）。在1806年出版的《精神疾病论述》(Treatise on Insanity)中，法国医生菲利普•皮内尔(Philippe Pinel)指出，当12月和1月的寒冷天气来临时，他的一些精神病患者的精神状况会恶化。
然而，最重要的一种理论是”阶段转换假说”(phase-shift hypothesis)：这种理论认为，白昼变短会延缓褪黑素的分泌，从而导致人体的昼夜节律与真正的时间不同步。褪黑素水平通常会随着黑夜的来临在夜间升高，让我们感觉昏昏欲睡，而清晨的明亮光线会抑制这种激素的分泌。美国佛蒙特大学(University of Vermont)心理学教授凯利•罗翰(Kelly Rohan)表示：”如果某人的生物钟变慢了，褪黑素水平居高不下，那么哪怕他们的闹钟响了，他们也知道自己必须为了谋生而去上班，但生物钟仍然会让他们赖在床上。”严格来说，生物钟失调为何会带来抑郁目前还不清楚。有一种理论认为，这种疲惫感会引发一系列不利于健康的连锁反应。如果疲惫感让你产生了一些负面想法，那么你可能会感到悲伤，对食物失去兴趣，继而出现其他症状。
然而，最近科学家们又研究了鸟类和小型哺乳动物对白昼长度变化做出的反应，这些研究结果为我们提供了另一种解释。据美国加州大学圣迭戈分校(University of California, San Diego)精神病学名誉教授丹尼尔•克里普克(Daniel Kripke)称，当褪黑素影响到大脑中的下丘脑区域，就会改变另一种激素——活跃甲状腺激素——的合成，这种激素负责调节人体的各种行为和生理过程。
一位名叫奥斯卡•柯蒂尔森(Oscar Kittilsen)的会计第一个想到了在留坎镇北面山坡上安装大型旋转镜的主意，根据他的设想，这些镜子可以”先捕捉阳光，然后把它播撒下来，就像头顶的照明灯一样照耀着留坎镇和镇上快乐的居民” 。
然而，还有一种解释认为，这种对黑暗的明显抵抗力是受文化因素影响。特罗姆瑟大学(University of Tromso)研究快乐的心理学家约•维特索(JoarVitterso)表示，”简单粗暴地来说，来到这里的人似乎可以分为两种，第一种人恨不得尽早回南方的城镇另外找份工作，另一种人却能安之若素地留在这里。”
在2014年到2015年期间，斯坦福大学(Stanford University)心理学家卡里•莱博维茨(Kari Leibowitz)在特罗姆瑟呆了10个月，试图搞清楚当地人是如何应对黑暗寒冬的。她和维特索合作设计了一套”冬季精神状态问卷”来评估特罗姆瑟、斯瓦尔巴群岛(Svalbard)和奥斯陆地区的人们对待冬天的态度。莱博维茨告诉我，越往北走，人们看待冬天的态度就越积极。”在南边，人们对冬天不喜欢的程度都差不多。不过从总体上看，喜欢冬天的人们对生活的满意度更高，也更愿意接受能带来个人成长的挑战。”