Few people enjoy the gloom that comes with winter in the world's higher latitudes. In up to a tenth of the population, the long nights can trigger a type of depression known as seasonal affective disorder (SAD). The exact physiological underpinnings of the disorder are not clear. Possible culprits include lower levels of melatonin, a hormone that regulates sleeping patterns; a drop in levels of serotonin, a neurotransmitter; and disruption to the body's internal circadian clock, which controls all sorts of bodily processes.

在世界高纬度地区，鲜少有人喜欢冬季的阴沉。 该地区多达十分之一的人口中，漫长的黑夜可能引发一种名为“季节性情感障碍”（SAD）的抑郁症。 这种疾病的确切生理机制尚不明确， 可能的诱因包括：调节睡眠模式的激素——褪黑素水平降低；神经递质——血清素水平下降； 以及控制人体各类生理过程的内在生物钟紊乱。

Antidepressants may help. But those often come with side-effects. Many people prefer to treat the root cause by buying gadgets designed to emit bright light, in the hope of banishing the gloom that causes SAD in the first place. All sorts are available, from devices that look like ordinary desk lamps to ones that resemble a tablet or smartphone on a stand. Many doctors recommend them as a first-line treatment for the disorder.

抗抑郁药物或许能起到缓解作用。 但这些往往伴随着副作用。 许多人更倾向于从根源解决问题，他们会购买强光发射设备， 希望借此直接驱散诱发季节性情感障碍的阴郁情绪。 这类设备种类繁多，既有外观类似普通台灯的款式，也有支架上放置着类似平板或智能手机造型的产品。 许多医生将其列为治疗该疾病的一线方案。

How well they actually work is tricky to test. In a drug trial, for instance, it is relatively straightforward to give some patients the real thing and others a placebo sugar pill. But running that sort of trial with light therapy would mean preventing a large group of people from being exposed to anything resembling daylight for long periods of time. Even if you can find the volunteers, doing so is only really feasible in big institutions such as hospitals and care homes. A few studies have been done along these lines. Most, though, have to make do with less rigorous control.

要测试这些设备的实际效果并非易事。 以药物试验为例，给部分患者服用真药、给另一部分患者服用安慰剂糖丸，操作相对简单。 但要开展强光疗法的类似试验，就需要让大量受试者在长时间内不接触任何类似日光的光线。 即使你能找到志愿者，这种试验也只有在医院、养老院等大型机构中才有可能实现。 目前已有少数此类研究， 但大多数相关试验都只能采用严谨度较低的对照方式。

With those caveats in mind, the evidence looks good. Last year a review of 21 studies, led by Tu Zhe-Ming at the Jingzhou Mental Health Centre in China, concluded that light therapy does indeed seem to work. Another review was published in March by Mihaela Bucuta, a psychologist at the Lucian Blaga University of Sibiu, in Romania, and her colleagues. It concluded that between 60% and 90% of patients see "symptom remission" with daily use.

尽管存在这些限制条件，现有证据仍显示出积极结果。 去年，中国荆州精神卫生中心的涂哲明（Tu Zhe-Ming）主导了一项涵盖21项研究的综述， 结论表明强光疗法确实有效。 今年3月，罗马尼亚锡比乌卢西恩・布拉加大学的心理学家米哈埃拉・布库塔及其同事发表了另一篇综述， 研究得出的结论是，每日使用强光设备的患者中，有60%至90%会出现“症状缓解”。

As for which devices are the most effective, those that emit predominantly blue, green or white light all seem to have a similar impact. And intensity may be less important than the claims made in lamp advertising would have you believe. Many boast that they can reach brightnesses of around 10,000 lux—far brighter than standard indoor lighting, and closer to the outdoors on a reasonably nice day. But less intense light seems to work, too, though the lamp may need to be on for longer.

至于哪种设备效果最佳，目前来看，主要发射蓝光、绿光或白光的设备，效果似乎相差无几。 而且光照强度的重要性，可能不如灯具广告宣称的那般高。 许多产品标榜自身亮度可达约10000勒克斯——远高于普通室内照明， 接近天气较好时的户外光照强度。 但强度较低的光线同样有效，只是可能需要延长设备开启时间。

Nor do there seem to be many drawbacks. Although a few users report experiencing headaches, eye irritation and blurred vision, such complaints are rare.

强光疗法的弊端似乎也不多。 尽管有少数使用者反映出现头痛、眼睛不适和视力模糊等症状，但这类情况十分罕见。

The benefits appear to be significant enough that a good deal of research has been done into whether light therapy can help patients with other, non-SAD forms of depression. Here, again, the findings seem promising. Dr Bucuta's review concluded that light therapy by itself can help with depression in 44% of cases. When it is combined with antidepressants, that number rises to 76%. Observations such as this have led researchers to run experiments comparing the results of drug or light therapy on their own with a combination of the two. The results again suggest that doing both together seems to produce better results than taking drugs alone.

鉴于强光疗法的益处显著，已有大量研究探讨其能否帮助非季节性情感障碍的其他抑郁症患者。 目前来看，研究结果同样颇具前景。 布库塔博士的综述指出，仅使用强光疗法，就能在44%的病例中缓解抑郁症状； 若与抗抑郁药物联用，这一比例会升至76%。 基于此类发现，研究人员开展了试验，对比单独使用药物、单独使用强光疗法，以及两者联用的效果。 结果再次表明，两者同时使用似乎比单独服用药物能产生更好的效果。

All that makes for a cheerful thought as the autumnal nights draw in. For those who suffer from winter depression, the light at the end of the tunnel may shine out of a lamp.

随着秋日夜晚临近，上述发现无疑是个令人振奋的消息。 对于那些受冬季抑郁困扰的人而言，黑暗尽头的光芒，或许正来自一盏强光lamp。