你有没有患过时差综合症，即由于长时间坐喷气飞机环球飞行跨越过很多时区而感到疲倦和沮丧?你有没有像北欧国家的很多人一样患过冬季忧郁症，即由于在阴郁的12月和1月老是看到冬日阴沉灰暗的天空而感到郁闷?也许一点点光就能解决你的问题——而且只需要照射你皮肤上一小块地方。实际上，美国科学家已竭尽全力进行研究——用光照射受试者的膝盖后部，试验光在提神方面的作用。
对付时差综合症和冬季忧郁症的东西可能是荷尔蒙褪黑激素。已知荷尔蒙褪黑激素能调节人体节奏。它于夜幕降临时分泌，可用于帮助治疗时差综合症和睡眠紊乱。冬天光线昏暗、白昼时间短，人们褪黑激素分泌较少，据说这就是许多人在天气昏暗时普遍有这种感觉(即冬季忧郁)的原因。
许多年来，专家们一直在试验用光治疗时差综合症和季节性情绪失调(“冬季忧郁证”)。他们建议患者坐在模仿太阳光自然波长的灯光前，以恢复褪黑激素。1996年，哈佛大学医学院的戴安娜·波文及其同事发现即使是昏暗的台灯也可以起到同样的作用。
动物和人接触光都会引起体内复杂的反应。纽约一个大学的研究小组说他们发现光照射在皮肤上会重新调整体内的生物钟。他们选择了胭窝做试验是因为那儿容易接触到而且远离眼睛，许多科学家认为那个部位决定着人体节奏的周期。
Scientists Shed New Light On The Body's Rhythms
Have you ever suffered from jet-lag, the fatigue and depression
that comes from long hours spent in a jet aircraft traveling across
the world over many time zones? Or like many people in northern
European countries, have you ever suffered the dark depression of
winter blues, the feelings of gloom that comes from facing the
somber December and January winter days under dark, cloudy skies?
Maybe all you need is a little light -- and merely on a small patch
of your skin. In fact, in experiments investigating the effect of
light in raising our spirits, American scientists have done all
their research using light played on the back of the subjects'
knees.
What could be a key to jet-lag and winter blues is the hormone
melatonin, which is known to regulate body rhythms. It is secreted
as night falls and it can be used to help to overcome jet-lag and
some sleep disorders. The low level of melatonin we experience in
winter when light is dull and daylight hours are shorter is said to
be cause of that common feeling many people get in dull weather --
winter depression.
For years experts have experimented with treating jet-lag and
seasonal affective disorder ("winter depression") with light. They
counsel victims to sit in front of lights simulating the sun's
natural wavelengths to restore melatonin. In 1996, Diane Boivin and
colleagues at Harvard Medical School found even dim reading lamps
worked in this way.
Exposure to light sets off a complex response inside the bodies of
animals and humans. A university team in New York said they had
found that shining light on the skin could re-set the body's
internal clock. They chose the back of the knee because it was easy
to reach and away from the eyes, which is where many scientists had
bdieved circadian rhythm is determined.
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