研究：左撇子易患心理疾病

《神经心理学》期刊发表的一篇最新研究发现，左撇子的人面临更多的心理健康问题，包括多动症、失读症，甚至精神分裂症。数据表明，左撇子的人和双手通用的人患心理疾病的概率高。他们占人口总数的比例分别为10%和1%，而可能患精神分裂症的比例却高达20%和30%。然而，《华尔街日报》也报道了一些好消息，比如左撇子的人有更好的发散思维和创造性。不仅如此，美国前任十届总统中，有六位都是左撇子，其中包括奥巴马和布什。截止目前，医生仍不能确定是什么原因导致用手的偏好，但发现环境因素，特别是子宫内的压力起着重要作用。例如，大龄产妇或体重轻的婴儿更容易是左撇子。人们常说左撇子的人使用右脑，用右手的人使用左脑，这种说不一定完全准确，但却可以解释为什么左撇子的人更容易遭遇心理障碍。

New research published in the journal Neuropsychologia finds that left-handed people are at increased risk for certain mental health issues, including ADHD, dyslexia and even schizophrenia.

For example, while left-handed people make up only 10 percent of the population, 20 percent of schizophrenics are left-handed. And those who are ambidextrous (able to use both hands), only an estimated 1 percent of the total population, may be even more at risk; 30 percent of schizophrenics are ambidextrous.

However, the Wall Street Journal reports there is also good news for lefties of the world, (of which I am one):

On average there is no significant difference in IQ between righties and lefties, studies show, belying popular perceptions. There is some evidence that lefties are better at divergent thinking, or starting from existing knowledge to develop new concepts, which is considered an element of creativity.

And whatever their political persuasion, lefties are in good company: Six of the past 10 presidents, including both Barack Obama and George H.W. Bush, have been left-handed.

Still, left-handed people, perhaps owing to their greater artistic inclination, tend to earn about 10 percent less in annual salaries than their right-handed counterparts, according to a recent Harvard University study.

Doctors are still unable to determine what causes hand preference but are finding that environmental factors, particularly stress in the womb, may play a leading role:

Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example. And mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child. A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.

People commonly say that left-handed people operate with the right side of their brain, while right-handed people use the left side. And to some extent, that's not only proving to be true, but may also explain why lefties are slightly more prone to psychological disorders:

Some 70% of lefties rely on the left hemisphere for their language centers, a key brain function, says Metten Somers, a psychiatrist and researcher who studies brain lateralization at Utrecht University Medical Center in the Netherlands. This doesn't appear to present problems, scientists say. The other 30% of lefties appear to exhibit either a right-dominant or distributed pattern, Dr Somers says. They may be more prone to impaired learning or functioning, and at greater risk for brain disorders, he says.