Mothers with an authoritative parenting style can influence the friends of their teenagers, making it less likely they will get drunk, or smoke cigarettes or marijuana, suggests a new study.

Friends of teens with strict mothers were 40 percent less likely to get drunk, 38 percent less likely to engage in binge drinking, 39 percent less likely to smoke cigarettes, and 43 percent less likely to smoke marijuana, compared with friends of adolescents with less strict mothers.

“Authoritative parenting — using a style that balances warmth and communication with appropriate control and supervision — is not only associated with reduced substance abuse in our own children, but it is also associated with reduced substance abuse in our own children’s friends,” lead researcher Holly Shakya of the University of California, San Diego School of Medicine told HealthDay.

“We also find that some of the effect may be spreading through the adolescent social network — parents’ behaviors affect their children, and that effect spreads to their friends,” Shakya added. “So, good parents may be helping both their own children and the friends of their children. Thus, the benefits of parenting interventions may be multiplied throughout the community beyond parent to child.”

The study appears in the Archives of Pediatric and Adolescent Medicine.