研究:冬季出生或可诱发心理疾病

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."

田纳西范德堡大学研究人员的最新研究显示，在冬季出生的孩子更容易出现心理健康问题。

研究人员们将一组小鼠在“夏季”模拟光照周期下(光照16小时，无光照8小时)从出生培养至断乳期，而将另一组小鼠在“冬季”模拟光照周期下(光照8小时，无光照16小时)培养至相同时间。第三组小鼠的培养情况则是一天12小时光照，12小时无光照。

随后，“冬季”小鼠中的一半仍在“冬季”周期中生长，另一半则被转移至“夏季”周期。而“夏季”小鼠也按同样分法被一分为二。在光照、非光照时间相同的条件下成长的小鼠被分为三组，一组继续享受12小时光照、12小时黑暗的生活，一组加入“冬季”组，而另一组加入“夏季”组。

28天后，研究人员发现，“夏季”出生的小鼠无论继续留在“夏季”周期还是被调换到“冬季”周期，表现都是一样的。然而在“冬季”出生的小鼠中，仍留在“冬季”的小鼠继续它们10小时清醒、14小时休息的生活，而被调换到“夏季”的小鼠活跃时间比前一组多了一个半小时。这意味着从出生到断乳一直在“冬季”模拟光线周期成长的小鼠的生物钟被打乱了。

(季节对生物钟有影响)这一结果在哺乳动物身上还是首次发现，并可能解释为什么在冬季出生的人群更易出现心理健康问题，包括狂躁抑郁症、精神分裂症以及季节性精神紊乱。

“我们已经知道生物钟控制着人类的情绪，”研究人员麦克马洪说道。“如果有一种同我们在小鼠身上得到的研究结果相似的胚教机制在人体内起作用，那么该机制不仅同一系列行为问题有关，还会对人格产生更为广泛的影响。”