In a long-term study conducted across three generations, researchers found that substance use in one generation was associated with problem behaviors and later substance use in the following generation. In turn, the substance use in the second generation was related to problem behaviors in the third generation.

The findings suggest that "not only does parent's substance use affect their children but it also can affect their grandchildren," study co-author Jennifer A. Bailey, of the University of Washington, in Seattle, Washington, told Reuters Health.

On the other hand, "the benefits of successful intervention may also echo across generations," Bailey and her co-authors write, so the findings highlight the importance of interrupting the intergenerational cycle.

For the current study, Bailey and her team analyzed data from the Seattle Social Development Project (SSDP), which includes 808 individuals who were followed from the age of 10 to 27, and The Intergenerational Project, which included study participants from the SSDP group who had a biological child. The researchers explored substance use and problem behaviors among the original 808 study participants as well as among their parents and their children, who ranged in age from 1 to 13 years old.

They found that grandparents who smoked, used marijuana, or engaged in heavy drinking were more likely to have children with problem behaviors, such as attention problems and stealing, during adolescence. These problem behaviors at ages 13 to 14 were associated with later substance use at ages 15 to 18, during early adulthood, and at age 27, the investigators report in the Journal of Abnormal Child Psychology.

Moreover, substance use among 27-year-olds in the second generation was associated with problem behaviors among their children as well, the third generation studied, the report indicates.

"Children of smokers, heavy drinkers or marijuana users are more likely to have behavior problems when they are young, and consequently more likely to have drug problems themselves as they get old," Bailey said in a university statement. "These children then grow up to be adult substance users, whose kids have behavior problems and the cycle is repeated," she explained.

Overall, over half (57 percent) of grandparents reported any substance use. Twenty-eight percent reported binge drinking and 11 percent reported using marijuana.

Cigarette smoking among grandparents, as was reported by 43 percent of them, was linked specifically to cigarette smoking among their children, as well as an increased tendency toward substance use in general, the study findings indicate.

This is significant because although people may expect children of smokers to be smokers themselves, Bailey said, they may "not realize that (smoking) also makes your kids more likely to drink heavily and use other drugs as well."

Yet, the associations reported in the study were only modest, and not deterministic for children of substance users, the researchers note.

"It's not like the children of substance users are fated to use substances themselves," Bailey said. "They're more likely, but not all that much more likely."

Still, she and her co-authors write, "successful preventive interventions may not only reduce conduct problems and substance use and put youth on a positive track toward adult development, but may also affect positive development in the next generation."

The research was funded by grants from the National Institute on Drug Abuse.

SOURCE: Journal of Abnormal Child Psychology, June 2006.