研究:冬季出生或可誘發心理疾病

People born in the winter are more likely to suffer mental health disorders, according to a recent study carried out by researchers at Vanderbilt University in Tennessee。

Researchers raised baby mice from birth to weaning in either "summer" light cycles of 16 hours of light and eight hours of dark or "winter" cycles of eight hours of light and 16 hours of dark. A third group experienced 12 hours of light and 12 hours of dark a day。

Then half the winter mice stayed in a winter cycle, while half switched to a summer schedule. The summer mice were similarly split. The mice raised in equal periods of light and dark were split into three groups, one of which stayed on the 12-hour schedule, one of which joined the winter group, and one of which joined the summer subset。

After 28 days, it turns out the summer-born mice behaved the same whether they stayed on the summer cycle or switched to winter. But among the winter-born mice, those stayed in winter kept their 10-hours-on, 14-hours-off schedule, while whose that switched to summer stayed active for an extra hour and a half, which indicates that mice born and weaned in a winter light cycle showed dramatic disruptions in their biological clocks。

The finding is the first of its kind in mammals, and it could explain why people born in the winter are at higher risk for mental health disorders including bipolar depression, schizophrenia and seasonal affective disorder。

"We know that the biological clock regulates mood in humans," said study researcher McMahon. "If an imprinting mechanism similar to the one that we found in mice operates in humans, then it could not only have an effect on a number of behavioral disorders, but also have a more general effect on personality."

田納西範德堡大學研究人員的最新研究顯示，在冬季出生的孩子更容易出現心理健康問題。

研究人員們將一組小鼠在“夏季”模擬光照週期下(光照16小時，無光照8小時)從出生培養至斷乳期，而將另一組小鼠在“冬季”模擬光照週期下(光照8小時，無光照16小時)培養至相同時間。第三組小鼠的培養情況則是一天12小時光照，12小時無光照。

隨後，“冬季”小鼠中的一半仍在“冬季”週期中生長，另一半則被轉移至“夏季”週期。而“夏季”小鼠也按同樣分法被一分爲二。在光照、非光照時間相同的條件下成長的小鼠被分爲三組，一組繼續享受12小時光照、12小時黑暗的生活，一組加入“冬季”組，而另一組加入“夏季”組。

28天后，研究人員發現，“夏季”出生的小鼠無論繼續留在“夏季”週期還是被調換到“冬季”週期，表現都是一樣的。然而在“冬季”出生的小鼠中，仍留在“冬季”的小鼠繼續它們10小時清醒、14小時休息的生活，而被調換到“夏季”的小鼠活躍時間比前一組多了一個半小時。這意味着從出生到斷乳一直在“冬季”模擬光線週期成長的小鼠的生物鐘被打亂了。

(季節對生物鐘有影響)這一結果在哺乳動物身上還是首次發現，並可能解釋爲什麼在冬季出生的人羣更易出現心理健康問題，包括狂躁抑鬱症、精神分裂症以及季節性精神紊亂。

“我們已經知道生物鐘控制着人類的情緒，”研究人員麥克馬洪說道。“如果有一種同我們在小鼠身上得到的研究結果相似的胚教機制在人體內起作用，那麼該機制不僅同一系列行爲問題有關，還會對人格產生更爲廣泛的影響。”