题型：阅读理解 题类：常考题 难易度：普通
内蒙古自治区赤峰二中2019-2020学年高二上学期英语第一次月考试卷
Do you often feel like you want to wash your hands again and again? Or do you ever have the urge to line up the items on your desk? These all may be symptoms of obsessive-compulsive disorder (强迫症), or OCD, which affects about 2 percent of the world's population.
Those who suffer from OCD have difficulty finding successful treatment because doctors don't clearly understand its causes. But now, a new study has given hope for a future cure.
For the study, which was published in the journal Nature in October, researchers observed humans, dogs and mice. They discovered four genes that may be responsible for obsessive-compulsive behaviors in humans.
But why observe dogs and mice to learn about humans?
"Dogs, it turns out, are surprisingly similar to people," study author and geneticist Elinor Karlsson, of the Broad Institute of MIT and Harvard University, US, told NPR. "They're chasing their own tail or chasing shadows like normal, but they're doing it for hours."
In the study, researchers made a list of about 600 genes in mice, dogs and humans that they thought might cause OCD, reported NPR. They then compared those genes in two large groups of people – those who don't have OCD and those who do. In the end, they identified just four genes with mutations (突变) in the OCD group. The genes are active in a neurological pathway (神经通路) in the brain, which is believed to help control actions. But the mutations could block the neurological pathway.
For example, for people without OCD, when they finish washing their hands, a signal will come, telling them to stop. But for people with OCD, the neurological pathway is blocked, so the message isn't getting through. As a result, the person will continue to wash their hands.
"OCD and anxiety are kind of like learning disorders," Marcos Grados, an OCD researcher at Johns Hopkins University School of Medicine, told NPR. "Often with OCD, people have a fear of germs (细菌). You can't touch tables or door knobs (把手) and every time it's the same sensation (感觉). You didn't learn that the last time you touched a door knob, nothing happened. It's like touching it for the first time ever."
However, that doesn't mean people who have these genetic mutations will always have obsessive-compulsive behaviors, the researchers said. That's because the disorder also relies on other things, such as one's environment.
According to reports, various existing treatment methods have low success rates in patients. But now that we know where OCD comes from, let's hope we will soon find an effective way to treat it.
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