研究：左撇子易患心理疾病

《神經心理學》期刊發表的一篇最新研究發現，左撇子的人面臨更多的心理健康問題，包括多動症、失讀症，甚至精神分裂症。數據表明，左撇子的人和雙手通用的人患心理疾病的概率高。他們占人口總數的比例分別爲10%和1%，而可能患精神分裂症的比例卻高達20%和30%。然而，《華爾街日報》也報道了一些好消息，比如左撇子的人有更好的發散思維和創造性。不僅如此，美國前任十屆總統中，有六位都是左撇子，其中包括奧巴馬和布什。截止目前，醫生仍不能確定是什麼原因導致用手的偏好，但發現環境因素，特別是子宮內的壓力起着重要作用。例如，大齡產婦或體重輕的嬰兒更容易是左撇子。人們常說左撇子的人使用右腦，用右手的人使用左腦，這種說不一定完全準確，但卻可以解釋爲什麼左撇子的人更容易遭遇心理障礙。

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.