You're not alone if colder weather and longer nights make you feel down.

　　如果你会因为冷天气和夜晚变长而情绪低落，那你不是特例。

　　This well-known phenomenon, called seasonal affective disorder (SAD), might explain why people feel low, irritable, and lethargic in the winter months. For some, the condition can be serious and debilitating.

　　有一个知名度很高的现象，叫季节性情绪失调，又叫SAD，或许可以解释为什么有人会在冬季感到低落、易怒、没精力。

　　Although SAD is a recognised form of clinical depression, experts are still divided on what causes the condition, with some even arguing it doesn't exist. But my own research has found that your eye colour might actually be one factor determining whether or not you develop SAD.

　　虽然SAD已经是一种临床承认的抑郁形式，但专家们依旧没有对它的成因达成共识，有些专家甚至在质疑它是否真的存在。不过我的个人研究发现，你眼睛的颜色可能是决定你是否患SAD的一个因素。

　　We have uncovered evidence that a person's eye colour can have a direct effect on how susceptible they are to SAD.

　　我们已经发现了一些证据，表明人眼的颜色对他们患SAD的可能性有直接的影响。

　　Our study used a sample of 175 students from two universities (one in south Wales, the other in Cyprus). We found that people with light or blue eyes scored significantly lower on the seasonal pattern assessment questionnaire than those with dark or brown eyes.

　　我们的研究从两所大学抽取了175名学生，这两所大学一所位于南威尔士，另一所位于塞浦路斯。我们发现，浅色眼睛和蓝眼睛的人在季节性行为模式评估问卷上的得分要显著低于深色和棕色眼睛的人。

　　These results agree with previous research which found that brown or dark-eyed people were significantly more depressed than those with blue eyes.

　　这次的结果和以前的研究也相符：棕色或深色眼睛的人的抑郁程度要显著高于蓝眼睛的人。

　　The reason that eye colour may make some people more susceptible to depression or mood changes might be because of the amount of light an individual's eyes can process.

　　眼睛的颜色之所以会让一些人更容易抑郁或者情绪波动，可能是源自不同人的眼镜能够处理的光线量不同。

　　The retina is the part of our eyeball containing cells that are sensitive to light. When light enters the eye, these cells trigger nerve impulses that form a visual image in our brain.

　　视网膜是我们的眼球中含有感光细胞的那个部位。当光线进入眼镜的时候，这些细胞就会发出神经冲动，进而在我们的大脑中形成视觉图像。

　　In 1995, scientists discovered that some retinal cells, rather than forming an image, simply send information about levels of brightness from the back of the eye to the brain's hypothalamus.

　　在1995年，科学家们发现有些视网膜细胞并不会生成图像。这些位于眼珠的细胞会直接把光线的亮度信息传递给大脑中的下丘脑。

　　The hypothalamus is an important part of the brain which secretes hormones (such as oxytocin) that regulate temperature, hunger and sleep cycles.

　　下丘脑是大脑中很重要的一部分，它会分泌激素来调控体温、饥饿感和睡眠周期;这些激素中就包括催产素。

　　As the amount of blue and green light reaching the hypothalamus increases, the amount of melatonin decreases. Eyes with lower pigment (blue or grey eyes) are more sensitive to light.

　　当抵达视网膜的蓝光和绿光变多的时候，褪黑素的数量就会降低。而那些色素较少的眼睛(比如蓝眼睛和灰眼睛)对光线更敏感。

　　This means they don't need to absorb as much light as brown or dark eyes before this information reaches the retinal cells.

　　这也就意味着，在信息抵达视网膜细胞之前，这些眼睛需要吸收的光线比棕色和深色眼睛要少。

　　As such, people with lighter eyes release less melatonin during the fall and winter. This mechanism might provide light-eyed people with some resilience to seasonal affective disorder (though a smaller proportion may still experience SAD).

　　如此这般，浅色眼睛的人在秋冬季节释放的褪黑素会更少。这种机制或许让浅色眼睛的人更能抵御季节性情绪失调。(不过还是有少部分人会经历SAD)