Parents who stay close to their grown children have a positive influence well after they've left the nest, but those who overdo it and meddle too much endanger their relationship, several new studies suggest.

Findings by researchers at Brigham Young University and analyses of larger, nationally representative surveys by the non-profit research group Child Trends are among an early round of studies on the relationship between parents and young adult children, often referred to as "emerging adults." Most prior findings on parent-child relationships have been based on children or adolescents.

"You still do matter, even though your kids aren't under your roof," says Laura Padilla-Walker, a Brigham Young professor of human development. "It's still important for you to know what they're doing."

She was the lead author of two recent studies about emerging adults, published online in the "Journal of Adolescence" and the "Journal of Youth and Adolescence.

"One such study of 200 undergraduates and parents from four colleges around the country found that parental knowledge is associated with fewer risky behaviors in their children, including drinking, taking drugs and risky sexual activity. The finding mirrors earlier research on parents and adolescents.

But while the effects of monitoring are "generally good in middle and late adolescence, they have negative repercussions in early adulthood," says Jacinta Bronte-Tinkew, a senior scientist and the lead author of a Child Trends parental monitoring study.

Jeffrey Jensen Arnett, a psychologist at Clark University in Worcester, Mass., who coined the term "emerging adulthood," says these young adults "guard their independence zealously."

"If they felt parents were intruding too much, they'd just tell them less," he says. "If parents are still intruding and monitoring them closely, there will be resentment and conflict."

Sociologist James Cote of the University of Western Ontario in Canada, who has also studied young adults, is concerned because much of the research has focused on college students, who he says are a "select group to start with."

That's one reason the new studies from Child Trends - yet unpublished - are particularly significant.

They take a broad look by analyzing data from the National Longitudinal Survey of Youth, which includes responses from more than 4,000 young people who were ages 12-14 initially, and then again at age 20. These are nationally representative longitudinal surveys that followed a diverse group.

Elizabeth Hair, a senior research scientist and lead author of one Child Trends study, found that higher levels of parental monitoring and more family routines translated into less risk-taking behavior for their young adult kids.

"What is very important is that parents' involvement be age-appropriate," says Kristin Moore, a senior scholar who worked on all the new Child Trends research. "You should treat a 21-year-old very differently than a 16-year-old - and not every parent pulls off that very difficult balance."