States that want to reduce rates of adult smoking may consider implementing stringent（严厉的） tobacco restrictions on teens, suggests a new study by researchers at Washington University School of Medicine in St. Louis. The researchers discovered that states with more restrictive limits on teens purchasing tobacco also have lower adult smoking rates, especially among women. And compared with states with less restrictive limits, they also tend to have fewer adult heavy smokers.

The study is published online June 13 in the American Journal of Public Health.

"In most states for many years, it has been illegal to sell cigarettes to people under 18, but few provisions（规定） are in place to prevent those sales," said the study's first author Richard A. Grucza, PhD, associate professor of psychiatry. "This study shows that more restrictive policies can prevent teen smoking and be beneficial down the road."

Grucza's team evaluated data from an ongoing National Cancer Institute survey that monitors smoking behavior in all 50 states.

Studying information gathered from 1998 to 2007 from 105,519 individuals ages 18 to 34, the researchers looked at whether people ever had smoked, whether they currently were smoking, and, if they did smoke, whether they smoked more than 10 cigarettes per day.

They also looked at the smoking restrictions in place in states when the study subjects were 17 years old.

"We looked at age 17 because in most states, it was illegal for anyone under 18 to buy tobacco products," Grucza said.

But how individual states chose to enforce the laws varied. Grucza's team focused on nine smoking-related policies and found that in states with enforcement policies, not only did 17-year-olds have more difficulty purchasing cigarettes, but that when they reached their 20s or 30s, they were less likely to smoke.

"We estimated that if all states had effective policies in place, it would reduce the prevalence（流行） of smoking by about 14 percent and the rates of heavy smoking by 29 percent," he said.