Children born to parents with a history of cigarette smoking are more likely to light up than kids of people who never smoked, according to a new U.S. study.
Despite falling smoking rates across age groups, researchers found that children raised by current or even former smokers were about three times more likely to be smokers themselves during their teenage years than kids raised by parents who never smoked.
"Things are getting better, but we can see it's best among the consistent non-smoking households," said Mike Vuolo, the study's lead author from Purdue University in West Lafayette, Indiana.
Previous research has produced similar results, but the new study was based on 23 years of data on the smoking patterns of the parents in the study - 214 people who were ninth grade students in 1988 - to see whether their habits from adolescence onward were tied to their children's risk of smoking.
For example, Vuolo and his colleague, who published their findings in Pediatrics, were able to compare the children of never-smokers and people who had smoked consistently since high school.
They had data on 314 children of the original group of teens. In 2011, the kids of the second generation - all at least 11 years old - were asked if they had smoked cigarettes within the last year. Sixteen percent said yes.
Among the children of parents who had never smoked, about 8 percent reported smoking cigarettes during the past year.
That compared to between 23 percent and 29 percent of the children of current or former smokers.
The researchers also looked at the parents' "trajectories" of smoking for clues about the parental influence on the children's behavior.
They found that 23 percent of kids whose parents had smoked as adolescents but quit or reduced their smoking as young adults were smokers themselves.
Among kids whose parents had smoked little or not at all in high school but started smoking in adulthood, 29 percent were smokers.
And 25 percent of children whose parents had smoked consistently since high school were smokers.
In addition, children who said they had smoked during the last year were more likely to be older, to display more symptoms of depression and to have low grades and low self-esteem. They were also more likely to feel distant from their parents and to have an older sibling who smoked.
While the study can't prove that parental smoking caused the children to adopt the habit, Dr. Jonathan Winickoff, who has studied teen smoking behavior but wasn't involved in the new research, said the new results support past findings.
"I think the first confirmatory result is that if you are a parent who smokes, your teenage child has a three-fold increased risk of smoking," Winickoff, an associate professor in Harvard Medical School's Department of Pediatrics in Boston, said.
He added that there are several theories on why children of smokers may be at an increased risk of picking up the habit, including modeling their parents' behaviors, easy access to cigarettes and being "primed" for an addiction through second-hand smoke exposure.
He cautioned, however, that the new study can't determine whether a child's risk of becoming a smoker falls if the parents stop smoking early-on, such as in their early adult years, because the group that contained those early quitters also included some current light smokers.
"They can't say - based on these data - whether earlier parental quitting is associated with less smoking in their kids," he said.
The researchers also warn that their findings may not apply to all smokers, because only 15 percent of the people included in their survey had a bachelor's degree or more education and most had their first child at a fairly young age.
Vuolo added that they don't know whether these smoking rates in the second generation are an improvement over the past because they're only looking at one point in time. Going forward, they will be able to look at smoking rates over time as they collect more data.
"We're going to be able to answer that question," he said.