Good parenting may have a “spill-over” effect that protects not only one’s own child, but also the child’s peers. Researchers based at the University of California, San Diego, School of Medicine performed a longitudinal survey of a nationally representative sample of adolescents across the United States to evaluate the relationship between the parenting style of an adolescent’s peers’ parents and substance abuse in the adolescent.

They found that if an adolescent had a friend whose mother was authoritative, that adolescent was 40 percent less likely to drink to the point of drunkenness, 38 percent less likely to binge drink, 39 percent less likely to smoke cigarettes, and 43 percent less likely to use marijuana than an adolescent whose friend’s mother was permissive. The researchers controlled for the parenting style of the adolescent’s own mother, school-level fixed effects, and demographics. The results were only partially mediated by peer substance use.

“Social network influences may extend beyond the homogeneous dimensions of own peer or own parent to include extradyadic influences of the wider network,” the researchers suggested.

Shakya H, Chistakis N, and Fowler J. “Parental Influence on Substance Use in Adolescent Social Networks.” Arch Pediatr Adolesc Med. 2012. October 8 [Epub ahead of print]. http://archpedi.jamanetwork.com/article.aspx?articleid=1377497.