题目内容：
根据以下材料，回答题Smoking Can Increase Depressive Symptoms in Teens
While some teenagers may use cigarettes to "self-medicate" (自我治疗) against the blues (忧郁), scientists at the University of Toronto and the University of Montreal have found that smoking may actually __________ (51) depressive symptoms in some teens.
"This observational study is one of the few to examine the perceived __________ (52) benefits of smoking among teens, " says lead researcher Michael Chaiton, a research associate at the Ontario Tobacco Research Unit of the University of Toronto." __________ (53) cigarettes may appear to have self-medicating effects or to improve mood, in the long __________ (54) we found that teens who started to smoke reported higher depressive symptoms."
As part of the study, some 662 high school teenagers completed up to 20 questionnaires about their use of cigarettes to __________ (55) mood. Secondary schools were selected to provide a mix of French and English participants, urban and rural schools, and schools __________ (56) in high,moderate and low socioeconomic neighbourhoods.
Participants were divided into three __________ (57): never smokers; smokers who did not use cigarettes to self-medicate, improve mood or physical __________ (58); smokers who used cigarettes to self-medicate. Depressive symptoms were measured using a scale that asked how often participants felt too tired to do things; had __________ (59) going to sleep or staying asleep; felt unhappy, sad, or depressed; felt hopeless about the future; felt anxious or tense; and worried too much about things.
"Smokers who used cigarettes as mood __________ (60) had higher risks of elevated (提升)depressive symptoms __________ (61) teens who had never smoked, " says co-researcher Jennifer O'Loughlin, a professor at the University of Montreal Department of Social and Preventive Medicine.
"Our study found that teen smokers who reported emotional benefits from smoking are __________ (62)higher risk of developing depressive symptoms."
The __________ (63) between depression and smoking existsv __________ (64) among teens that use cigarettes to feel better. "It's __________ (65) to emphasize that depressive symptom scores were higher among teenagers who reported emotional benefits from smoking after they began to smoke, "says Dr. Chaiton.
回答(51)题 A．diagnose
B．increase
C．examine
D．treat
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