Alcohol, tobacco use declines among US teenagers: study

American teenagers were drinking and smoking less and did fewer drugs than their predecessors in over 40 years of tracking, according to a study.

Even the use of marijuana had gone down among 8th- and 10th-graders, though it continued to be flat among high school seniors, according to the annual Monitoring the Future survey of American teens.

''The question is: Why is all this happening?'' asked Lloyd Johnston, who has led the survey since it was begun in 1975, USA Today reported. ''Even though we have some hypotheses, I don't know that we necessarily have the right ones.''

According to Johnston and other experts,  a decline in smoking might be largely responsible for the broader decline. For young teens, smoking was a gateway to other illicit activities, and by cutting smoking rates, fewer adolescents were moving on to alcohol and drugs, said Johnston of University of Michigan's Institute for Social Research.

In 1991, nearly 11 per cent of high school seniors smoked a half pack of cigarettes or more a day, while this year 1.8 per cent reported smoking that much, and 10.5 per  cent reported any smoking in the last month.  Even e-cigarette use had fallen among  seniors, from 16 per cent last year to 12 per cent this year.

According to Nora Volkow, direct of the National Institute on Drug Abuse, which funded the study, that was good news for the nation and proof that drug prevention efforts had worked.

But she had a different explanation, ''The development of very, very fancy video games has resulted in a pattern of compulsive use of these games that may serve as a substitute for drug-taking,'' Volkow said in an interview, The Charlotte Observer reported. ''I'm speculating, but it needs to be tested.