VOA标准英语2009-Researchers Find No Link Between Defective G

US researchers reviewing more than a dozen studies say a defective¹ gene² that has been implicated³ as a cause of major depression does not appear to elevate a person's risk for the mood disorder⁴. The finding is viewed as a setback⁵ for researchers trying to identify a genetic⁶ basis for depression.

Major depression and other psychiatric disorders⁷ tend to run in families. So, researchers have been looking for the genetic culprits that predispose individuals to the mental disorder.

Discovery of an abnormal gene could lead to diagnostic blood tests to determine who is at risk for depression, and could provide an easier target for drugs used to treat the mood disorder.

The U.S. research team of geneticists, public health officials and epidemiologists, led by Kathleen Merikangas of the federally-funded National Institute of Mental Health, concluded after reviewing 14 studies involving over 14,000 individuals that there's no evidence a defective gene is the sole cause of major depression.

While it's long been established that stressful life events such as loss of a job or divorce can trigger depression, not everyone who experiences a major life change becomes depressed⁸.

So, Merikangas and her colleagues sought to test the finding of a much-hailed 2003 study which concluded that stressful life events were more likely to cause depression in people who also had a defective gene governing the transport of the brain chemical serotonin, a mood-stabilizing neural⁹ transmitter.

But Merikangas says subsequent studies that attempted to support the finding have been inconsistent.

"So it wasn't clear whether it was a real finding or whether we needed to learn more about the finding before we started to move in the direction of translating it into public health and prevention," said Merikangas.

While researchers found no direct link between the serotonin transporter gene and depression, they did discover the number of stressful life events increased the risk of depression in some individuals.

Peter Zandi, a researcher at Johns Hopkins University School of Public Health who has been looking for a genetic basis for major depression, calls the study's finding discouraging.

"The best way to confirm these sorts of associations is through replication," Zandi said. "And this particular paper that you cite suggests there isn't replicable¹⁰ evidence of this one particular gene which many in the field had been excited about."

Scientists say it is quite likely the serotonin transporter gene, in combination with other defective genes¹¹, contributes to depression.

That's because a class of drugs known as serotonin reuptake inhibitors, which include Prozac, Paxil and Zoloft, that target the abnormal transporter gene, relieve the symptoms of depression in some individuals.

Zandi says the study is not the final word on whether the genetic defect plays a major role in the development of depression.

"It's not conclusive¹² evidence that it's not. But by the same token, there isn't conclusive evidence that it is related to depression," said Zandi. "And after many years of trying to figure out what is going on with the genetic causes of depression, we're not there yet."

The findings of the study on a depression gene appear this week in Journal of the American Medical Association

1 defective   

adj.有毛病的，有问题的，有瑕疵的

参考例句：

• The firm had received bad publicity over a defective product. 该公司因为一件次品而受到媒体攻击。
• If the goods prove defective, the customer has the right to compensation. 如果货品证明有缺陷， 顾客有权索赔。

2 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

3 implicated   

adj.密切关联的；牵涉其中的

参考例句：

• These groups are very strongly implicated in the violence. 这些组织与这起暴力事件有着极大的关联。 来自《简明英汉词典》
• Having the stolen goods in his possession implicated him in the robbery. 因藏有赃物使他涉有偷盗的嫌疑。 来自《现代汉英综合大词典》

4 disorder   

n.紊乱，混乱；骚动，骚乱；疾病，失调

参考例句：

• When returning back,he discovered the room to be in disorder.回家后，他发现屋子里乱七八糟。
• It contained a vast number of letters in great disorder.里面七零八落地装着许多信件。

5 setback   

n.退步，挫折，挫败

参考例句：

• Since that time there has never been any setback in his career.从那时起他在事业上一直没有遇到周折。
• She views every minor setback as a disaster.她把每个较小的挫折都看成重大灾难。

6 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

7 disorders   

n.混乱( disorder的名词复数 )；凌乱；骚乱；（身心、机能）失调

参考例句：

• Reports of anorexia and other eating disorders are on the increase. 据报告，厌食症和其他饮食方面的功能紊乱发生率正在不断增长。 来自《简明英汉词典》
• The announcement led to violent civil disorders. 这项宣布引起剧烈的骚乱。 来自《简明英汉词典》

8 depressed   

adj.沮丧的，抑郁的，不景气的，萧条的

参考例句：

• When he was depressed,he felt utterly divorced from reality.他心情沮丧时就感到完全脱离了现实。
• His mother was depressed by the sad news.这个坏消息使他的母亲意志消沉。

9 neural   

adj.神经的，神经系统的

参考例句：

• The neural network can preferably solve the non- linear problem.利用神经网络建模可以较好地解决非线性问题。
• The information transmission in neural system depends on neurotransmitters.信息传递的神经途径有赖于神经递质。

10 replicable   

可复制的，能复现的

参考例句：

• The database must be closed to make the database replicable programmatically. 若要用程序将数据库设置为可同步复制，则必须关闭数据库。
• You must select a database with a least one replicable table. 必须选择一个具有一个以上可复制表的数据库。

11 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

12 conclusive   

adj.最后的，结论的；确凿的，消除怀疑的

参考例句：

• They produced some fairly conclusive evidence.他们提供了一些相当确凿的证据。
• Franklin did not believe that the French tests were conclusive.富兰克林不相信这个法国人的实验是结论性的。