我们常说春困秋乏。英文中也有类似“秋乏”的说法。天气转凉，心情低落，做事乏味，这被称作是冬季忧郁（winter depression），更科学的说法是“季节性情感失调”。研究认为，冬季忧郁也是抑郁症的一种。症状严重的，无法正常工作生活。话说古人悲秋作诗词，难道也是受了季节性情感失调的影响？（欢迎收看今天的走近科学...）
秋天没力气上班，可能是抑郁症
作者：David Cox
译者：王乐颖
校对：李林治
词汇：徐 唱
策划：朱雨晴
The science of Sad: understanding the causes of ‘winter depression’
了解季节性情感失调：什么引发了“冬季忧郁”
本文选自 The Guardian | 取经号原创翻译
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The darker days and colder weather can bring with them a feeling of low spirits. So, what makes people susceptible to seasonal affective disorder, and what are the best ways to treat it?
白天变短，天气转凉，可能会让人觉得精神倦怠。 那么，为什么有人会季节性情感失调？如何治疗最好呢？
susceptible /səˈseptɪbəl/ adj. likely to suffer from a particular illness or be affected by a particular problem. 易受影响的
For many of us in the UK, the annual ritual of putting the clocks back for daylight saving time can be accompanied by a distinct feeling of winter blues as autumn well and truly beds in. This might be felt as a lack of energy, reduced enjoyment in activities and a need for more sleep than normal. But for around 6% of the UK population and between 2-8% of people in other higher latitude countries such as Canada, Denmark and Sweden, these symptoms are so severe that these people are unable to work or function normally. They suffer from a particular form of major depression, triggered by changes in the seasons, called seasonal affective disorder or Sad.
对于很多英国人来说，夏令时结束，又该把时钟往回拨一小时了，年年如此。这也意味着秋天真的来了，此时，人们可能会明显地感到一种冬天的忧愁。你可能会感觉缺乏活力，日常活动乐趣减少，需要比正常更多的睡眠。但是对于英国约6％的人口，以及如加拿大，丹麦和瑞典这样高纬度国家的2-8％的人来说，这些症状非常严重，以至于他们无法正常工作或生活。他们患有一种特殊的抑郁症，由季节变化引发，称为季节性情感失调（英文缩写为Sad）。
In addition to depressive episodes, Sad is characterised by various symptoms including chronic major and extreme carbohydrate cravings that lead to weight gain. As this is the opposite to major depressive disorder where patients suffer from disrupted sleep and loss of appetite, Sad has sometimes been mistakenly thought of as a “lighter” version of depression, but in reality it is simply a different version of the same illness. “People who truly have Sad are just as ill as people with major depressive disorder,” says Brenda McMahon, a psychiatry researcher at the University of Copenhagen. “They will have non-seasonal depressive episodes, but the seasonal trigger is the most common. However it’s important to remember that this condition is a spectrum and there are a lot more people who have what we call sub-syndromal Sad.”
除了抑郁发作之外，季节性情感失调还有各种症状，包括长期嗜睡和对碳水化合物的极度渴求，后者会导致体重增加。由于这与严重的抑郁症状相反，抑郁症患者无法安睡，食欲不振，季节性情感失调有时被误认为是“较轻”的抑郁症，但实际上这只是同一种疾病的不同版本。哥本哈根大学精神病学研究员布伦达·麦克马洪说：“真正患有季节性情感失调的人，和抑郁症患者的病情一样严重。他们会有非季节性的抑郁发作，但季节性发病是最常见的。然而，重要的是，这种失调症的症状多种多样，更多人患的是所谓的季节性情感失调分症候群。”
characterize /ˈkærɪktəraɪz/ v. to describe the qualities of someone or something in a particular way. 描述(人或物)的特性
Around 10-15% of the population has sub-syndromal Sad. These individuals struggle through autumn and winter and suffer from many of the same symptoms but they do not have clinical depression. And in the northern hemisphere, as many as one in three of us may suffer from “winter blues” where we feel flat or disinterested in things and regularly fatigued.
大约10-15％的人口患有季节性情感障碍分症候群。这些人秋冬季苦苦挣扎，患有许多相同的症状，但没有临床意义上的抑郁症。在北半球，三分之一的人可能会“冬日忧郁”，对事物淡漠或不感兴趣的，并经常感到疲惫不堪。
fatigued /fəˈtiːgd/ adj. extremely tired 疲惫的
One theory for why this condition exists is related to evolution. Around 80% of Sad sufferers are women, particularly those in early adulthood. In older women, the prevalence of Sad goes down and some researchers believe that this pattern is linked to the behavioural cycles of our ancient ancestors. “Because it affects such a large proportion of the population in a mild to moderate form, a lot of people in the field do feel that Sad is a remnant from our past, relating to energy conservation,” says Robert Levitan, a professor at the University of Toronto. “Ten thousand years ago, during the ice age, this biological tendency to slow down during the wintertime was useful, especially for women of reproductive age because pregnancy is very energy-intensive. But now we have a 24-hour society, we’re expected to be active all the time and it’s a nuisance. However, as to why a small proportion of people experience it so severely that it’s completely disabling, we don’t know.”
为什么会有这样的病症存在呢？其中一种解释说与进化有关。季节性情感失调的病患中大约80％是女性，特别是刚成年的女性。在年纪更大的女性中，季节性情感失调的患病率下降，一些研究人员认为这种模式与我们古代祖先的行为周期有关。多伦多大学的罗伯特·列维坦教授说：“因为它轻微地影响着如此大比例的人口，很多人真切地感到季节性情感障碍是过去的遗留问题，涉及到节约能源。一万年前，在冰河时代，这种在冬季减缓的生理趋势是有用的，特别是对于生育年龄的妇女来说，因为怀孕非常耗能。但现在我们的社会24小时运转，社会期待我们一直积极，这令人讨厌。但是，我们不清楚为什么有一小部分人症状如此严重，以致于完全无法正常生活。”
prevalence /ˈprɛvələns/ n. the state of common at a particular time, in a particular place, or among a particular group of people. 普遍、流行
nuisance /ˈnjuːsəns/ n. a person, thing, or situation that annoys you or causes problems. 讨人厌的东西或人
There are a variety of biological systems thought to be involved, including some of the major neurotransmitter systems in the brain that are associated with motivation, energy and the organisation of our 24-hour circadian rhythms. “We know that dopamine and norepinephrine play critical roles in terms of how we wake up in the morning and how we energise the brain,” Levitan says. One particular hormone, melatonin, which controls our sleep and wake cycles, is thought to be “phase delayed” in people with severe Sad, meaning it is secreted at the wrong times of the day.
这一症状被认为涉及到许多生物系统，包括与运动、能量和人类24小时昼夜节律有关的脑中主要的神经递质系统。列维坦说：“我们知道多巴胺和去甲肾上腺素在我们早上醒来、激活大脑时起关键作用。控制我们的睡眠和觉醒周期的一种特殊激素——褪黑素被认为是忧郁症严重的人的 ‘相位延迟’，这意味着它分泌时间错误。”
Another system of particular interest relates to serotonin, a neurotransmitter that regulates anxiety, happiness and mood. Increasing evidence from various imaging and rodent studies suggests that the serotonin system may be directly modulated by light. Natural sunlight comes in a variety of wavelengths, and it is particularly rich in light at the blue end of the spectrum. When cells in the retina, at the back of our eye, are hit by this blue light, they transmit a signal to a little hub in the brain called the suprachiasmatic nucleus that integrates different sensory inputs, controls our circadian rhythms, and is connected to another hub called the raphe nuclei in the brain stem, which is the origin of all serotonin neurons throughout the brain. When there is less light in the wintertime, this network is not activated enough. In especially susceptible individuals, levels of serotonin in the brain are reduced to such an extent that it increases the likelihood of a depressive episode.
另一个会影响人的系统是血清素，它是一种调节焦虑、快乐和情绪的神经递质。越来越多来自各种成像和啮齿动物研究的证据表明，血清素系统可能直接由光调节。自然光照有各种波长，而光谱的蓝色端则特别丰富。当我们眼睛后面的视网膜细胞受到这种蓝光的照射时，它们将信号传递给大脑中的一个小枢纽，称为视交叉上核，这一枢纽集成了不同的感觉输入，控制着我们的昼夜节律，并且与另一个叫做脑干中缝核的中枢相连，这一中枢是整个大脑中所有血清素神经元的起源。当冬天的光线较少时，这一神经网络无法激活。在特别敏感的个体中，大脑中血清素的水平还会降低，增加抑郁发作的可能性。
modulate /ˈmɔdjʊleɪt/ n. to change a process or activity to make it more controlled, slower, less strong etc. 调节
Serotonin may also explain why women are so much more vulnerable to Sad than men. “There’s a close connection between estradiol, the main female sex hormone, and the serotonin transporter,” McMahon says. “We have a good idea that the fluctuating levels of estradiol during certain phases such as puberty or postpartum, can affect the way serotonin is produced.”
血清素也可以解释为什么女性比男性更容易得季节性情感失调。麦克马洪说：“雌性激素——雌二醇——和血清素转运蛋白之间，有着密切的联系。我们有一个靠谱的想法，在某些阶段，如青春期或产后，雌二醇的波动水平会影响血清素的产生方式。”
fluctuating /'flʌktʃueitiŋ/ adj. if a price or amount fluctuates, it keeps changing and becoming higher and lower. 起伏
Some populations appear to be particularly resilient to Sad, mostly notable in Iceland. “Icelanders seem to be genetically protected from Sad,” Levitan says. “When they move to locations which have high rates of Sad such as Canada, their rates are much lower than their peers.” One possible reason for this could again be linked to serotonin. There are different variants of a gene that controls how the serotonin transporter behaves, and one particular variant found in resilient individuals actually causes our bodies to increase the production of serotonin during the wintertime.
有些人似乎对季节性情感失调特别有抵抗力，最著名的要属冰岛人。“冰岛人似乎受到遗传保护，不会患SAD这种病。” 列维坦说, “当他们搬到像加拿大这样患病率高的地方时，他们的患病比率比同龄人低得多。” 这可能仍与血清素有关。有一种基因的不同变体可以控制血清素转运蛋白的表现，而在耐受性大的个体中发现的一种特殊的变体，实际上会让他们的身体在冬季生成更多血清素。
resilient /rɪˈzɪliənt/ adj. able to become strong, happy, or successful again after a difficult situation or event. (指人的性格)能迅速恢复或重新振作的;达观的;适应性强的
For those on the Sad spectrum, there are a variety of treatments available, the most popular being bright-light therapy, an artificial means of stimulating the brain’s neurotransmitters. “It’s very important to use a Sad-specific ultraviolet filtered light otherwise it can be dangerous,” says Levitan. “But it can really enable people with Sad to get their day started earlier and avoid oversleeping, which can be very depressogenic. It’s probably effective in providing symptom relief in around 80% of patients, particularly those with the carbohydrate craving, oversleeping symptoms. For the most severe patients, though, it may have to be combined with antidepressant therapy.”
对于那些受季节性情感失调困扰的人群来说，市面上有各种各样的治疗手段。最流行的是亮光疗法，这是一种人为刺激大脑神经递质的手段。“一定要使用专门治疗季节性情感失调的紫外线过滤灯，否则可能会非常危险。” 列维坦说：“但是过滤灯真的可以让季节性情感失调病患早点起床，避免极有可能造成抑郁的过度睡眠。对80％左右的患者，特别是那些渴望碳水化合物、睡眠过度症状的患者，减轻症状是有效的。但对于症状极为严重的患者，可能需要联合抗抑郁药治疗。”
However, psychiatrists urge patients to steer clear of some of the many alternative therapies on the market. “There’s a range of new technologies people are developing, such as an earplug that is supposed to radiate light into your brain, but there’s no science to prove that this actually works,” McMahon says. “However, there are some good additions to conventional light therapy and antidepressants, such as tryptophan, an amino acid that gets converted to serotonin in our bodies, which can be given as an add-on treatment.”
然而，心理学家呼吁病人避开市场上的许多替代疗法。“人们正在开发一系列新技术，比如一种所谓能够将光线幅射到大脑中的耳塞，但没有科学证明它是有效的。” 麦克马洪说，“然而，传统的光疗和抗抑郁药之外，还有一些很好的补充治疗。比如色氨酸，它是一种在我们体内转化为血清素的氨基酸，可作为附加治疗。”
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