一場大雪讓很多北方城市都提前進入冬季。因為天氣寒冷，很多人都愿意宅在家里，還有人會因為晝短夜長而有些情緒波動。這個冬季，你憂郁了嗎？

Seasonal affective disorder (SAD) is a type of depression that sets in or starts in the winter months. Unlike other types of depression, it may improve as spring comes on. It is often a cyclical, recurring disorder--you'll feel depression every winter and begin to feel better each spring.

季節(jié)性情緒紊亂（seasonal affective disorder，SAD）指多發(fā)于冬季的一種抑郁癥，也稱“冬季抑郁癥”。與其它類型的抑郁癥不同的是，這種季節(jié)性抑郁癥會在春天到來時有所好轉。這是一種循環(huán)的、反復發(fā)生的情緒紊亂，每年冬天時覺得抑郁，春天到來時又好轉了。

A study by Alfred Lewy at the Oregon Health and Science University found that most of the symptoms of seasonal affective disorder are caused by body rhythms that are not in sync with the sun. Often the body gets out of sync with the sun because of winter's shortened days. The pineal gland, which regulates body rhythms, secretes a hormone called melatonin during the night. This can affect your sleep wake cycle and other rhythms. When it gets dark too early in the day, the pineal gland and the body's sleep wake cycle get out of sync.

俄勒岡健康與科學大學的阿爾弗雷德?洛威所做的一項研究發(fā)現(xiàn)，季節(jié)性情緒紊亂的大部分癥狀是由身體節(jié)律與太陽不同步導致的。通常來說，身體會因為冬季白天變短而無法與太陽同步。控制身體節(jié)律的松果體會在夜間分泌一種叫做褪黑素的激素。這種激素會影響你的作息周期和其它節(jié)律。天黑得太早時，松果體和身體的作息周期就無法同步。

Seasonal affective disorder is far more common in northern climates, where days can be very short in winter. SAD affects more women than men and is likelier to occur in people under age 40 than those older than that.

季節(jié)性情緒紊亂在北方氣候地區(qū)更常見，北方冬季的白天都很短。該癥狀的女性患者多于男性，而且更易發(fā)生在40歲以下人群中。

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（中國日報網英語點津 Helen）

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