Surveys of parents and teenagers in America show a wide disparity between perceptions about parental influence on the choices adolescents make about drugs and alcohol.

Parents say they don't have much influence over their teenage children, but, surprisingly, teenagers admit that parents do have an influence.

A new report from the U.S. Substance Abuse and Mental Health Services Administration says more than one in five parents of teenagers believe they possess little influence over whether their child drinks alcohol or experiments with drugs and tobacco. Released on Friday, the report says 9.1 percent of parents of teenagers said they don't speak to their children about the health dangers of using alcohol, tobacco, and other drugs.

The government surveyed 67,000 Americans ages 12 and older as part of its annual National Survey on Drug Use and Health. Peter Delaney, director of the Center for Behavioral Health Statistics and Quality at the agency, said surveys of teenagers demonstrate that parental influence is much greater than previously thought. In big numbers, teenagers who believe their parents would strongly disapprove of substance abuse were less likely than their peers to use them.

"Any time is a good time to talk to your kids when you have a chance," Delaney said. "But if you haven't started talking to your kids, before school gets out is an especially good time."

Delaney warned that teenagers are more likely to try substances during the summertime, especially around holiday weekends like Memorial Day and the Fourth of July. "In the summer months, especially around holiday weekends, kids are more likely to get involved with substances," Delaney said. Holiday and summertime parties may offer kids access to substances, more so than the school year.

Agency administrator Pamela Hyde also encouraged parents to at least make the effort to influence their kids to make healthy choices. "Parents need to initiate age-appropriate conversations about these issues with their children at all stages of their development in order to help ensure that their children make the right decisions," she said.

However, that conversation about drugs and alcohol should change as children mature, according to Robert Lindsey, president and CEO of the National Council on Alcoholism and Drug Dependence. "Early on, it may be very basic information," he told USA Today. "As kids get older, we need to talk about the impact on health, academics, relationships, driving, and the dangers of alcohol and prescription drugs."

Just as important, parents should discuss with candor any family history and genetic predisposition for alcoholism and substance abuse, experts say, taking care to provide a good behavioral example for children as well.

For more information on how to have these important conversations, parents may consult the agency's guide Navigating the Teen Years: A Parent's Handbook for Raising Healthy Teens.

Source: U.S. Substance Abuse and Mental Health Services Administration. The NSDUH Report: Data Spotlight. 1 in 5 Parents Think What They Say Has Little Influence on Their Child's Substance Use. May 2013.