Passage Two
Questions 51 to 55 are based on the following passage.
　　Teenagers at risk of depression, anxiety and suicide often wear their troubles like a neon sign. Their risky behaviors—drinking too much alcohol, using illegal drugs, smoking cigarettes and skipping school—can alert parents and teachers that serious problems are afoot.
　　But a new study, published this month in the journal, finds that there’s another group of adolescents who are in nearly as much danger of experiencing the same psychiatric symptoms as their high-risk peers: teens who use tons of media, don’t get enough sleep and have a sedentary (不爱活动的)lifestyle.
　　Of course, that may sound like a description of every teenager on the planet. But the study warns that it is teenagers who engage in all three of these practices in the extreme who are truly in jeopardy. Because their behaviors are not usually seen as a red flag, these young people have been dubbed the “invisible risk” group by the study’s authors.
　　“In some ways they are at greater risk of falling through the cracks,” says Vladimir Carli. “While most parents, teachers and clinicians would react to an adolescent using drugs or getting drunk, they may easily overlook teenagers who are engaging in unobtrusive behaviors.”
　　The study’s authors surveyed 12,395 students and analyzed nine risk behaviors: excessive alcohol use, illegal drug use, heavy smoking, high media use and truancy(逃学). Their aim was to determine the relationship between these risk behaviors and mental health issues in teenagers.
　　About 58% of the students demonstrated none or few of the risk behaviors. Some 13% scored high on all nine of the risk behaviors. And 29%, the “invisible risk” group, scored high on three in particular: They spent five hours a day or more electronic devices. They slept six hours a night or less. And they neglected “other healthy activities.”
　　The group that scored high on all nine of the risk behaviors was most likely to show symptoms of depression; in all, nearly 15% of this cohort reported being depressed, compared with just 4% of the low-risk group. But the invisible group wasn’t far behind the high-risk set, with more than 13% of them exhibiting depression.
　　The findings caught Carli off guard. “We were very surprised,” he says. “The high-risk group and low-risk group are obvious. But this third group was not only unexpected, it was so distinct and so large—nearly one third of our sample—that it became a key finding of the study.”
　　Carli says that one of the most significant things about his study is that it provides new early-warning signs for parents, teachers and mental health-care providers. And early identification, support and treatment for mental health issues, he says, are the best ways to keep them from turning into full-blown disorders.