A new study suggests that the more teenagers watch television, the more likely they are to develop depression as young adults．But the extent to which TV may or may not be to blame is a question that the study leaves unanswered．
The researchers used a national long-term survey of adolescent health to investigate the relationship between media use and depression．They based their findings on more than 4,000 adolescents who were not depressed when the survey began in 1995．
As part of the survey, the young people were asked how many hours of television or videos they watched every day．They were also asked how often they played computer games and listened to the radio．
Media use added up to an average of five and one-half hours a day．More than two hours of that was spent watching TV．
Seven years later, in 2002, more than seven per cent of the young people had signs of depression．The average age at that time was twenty-one．
Brian Primack at the University of Pittsburgh medical school was the lead author of the new study．He says every extra hour of television meant an eight per cent increase in the chances of developing signs of depression．
The researchers say they did not find any such relationship with the use of other media such as movies, video games or radio．But the study did find that young men were more likely than young women to develop depression given the same amount of media use．
Doctor Primack says the study didn’t explore if watching TV causes depression．But one possibility, he says, is that it may take time away from activities that could help prevent depression, like sports and socializing．It might also interfere with sleep, he says, and that could have an influence．
The study was just published in the Archives of General Psychiatry．
In December, the journal Social Indicators Research published a study of activities that help lead to happy lives．Sociologists from the University of Maryland found that people who describe themselves as happy spend less time watching television than unhappy people．The study found that happy people are more likely to be socially active, to read, attend religious services and to vote．
51．According to the first paragraph,what remains unsolved in the new study?
A．Who is more likely to be influenced by TV
B．How much teenagers are depressed by TV
C．Whether teenagers are influenced by TV
D．What should be done to help to help the teenagers
52．More than 4,000 adolescents were chosen as the subjects of the study because they     ．
A．were free from depression
B．were keen on using the media
C．attached much importance to their health
D．could afford the time for the long term survey
53．What can be inferred from the seventh paragraph?
A．Depression is not related to the use of other media than TV
B．Every extra hour of media uses increases the chance of depression
C．Longer use of media other than TV doesn’t increase the chance of depression
D．The influence of movies,video games and radio on depression varies respectively
54．In the last sentence of the eighth paragraph, “It”refers to     ．
A．depression    B．watching TV     C．lack of activities    D．the result of the study
55．The study done by the sociologists from the University of Maryland was mainly intended to     ．
A．tell the difference between happy and unhappy people
B．prove the realationship between TV and depression
C．stress the importance of being socially active
D．provide a happy recipe（秘方）for all people