Movies, television shows, and music are no longer viewed by parents as the sole culprits behind smoking and alcohol use among teens. The Internet — specifically social networking sites — now plays an integral role in how information is disseminated, and can even exacerbate risky behavior in school-age children. Sites such as Facebook and Myspace can elevate levels of peer pressure because of easy accessibility and widespread usage in this age group. According to the Pew Internet & American Life Project report, 95 percent of teens (aged 12 to 17) use the Internet, and 81 percent of them use social networking sites like Facebook. With 94 percent of teens reporting that they have a Facebook profile, chances are that teens can exaggerate their risky behaviors (drinking, drug use, or sexual activity) through online posts and pictures to portray what they believe is a “cool” image of themselves.

“Things that you do, or you say that you do online, you have to do those same things in person in order to keep up that persona that you’ve built for yourself online,” said Sonya Negriff, assistant research professor at University of Southern California’s School (USC) of Social Work, to CBS Los Angeles. A teen’s closest friends are the strongest influence for behavior (good or bad), online or offline. Friends’ Facebook and Myspace photos are found to affect smoking and alcohol use among peers, according to a new study.

Findings published online in the Journal of Adolescent Health show a significant link between exposure to online content — portraying risky behavior, such as drinking and smoking — and teens’ dangerous behavior. Researchers from USC surveyed 1,563 10th grade students from the El Monte Union High School District in Los Angeles County in October 2010 and April 2011. The students, whose average age was 15, were asked about their online and offline friendship networks, social media use, and smoking and alcohol consumption.

El Monte, the ninth largest city in Los Angeles County, during the time of the study, had a population of about 113,500 with a prominent Latino and Asian population. Two-thirds of the survey respondents were Hispanic/Latino, and one-fourth were Asian.

Researchers noted that approximately half of all the students reported frequent use of Facebook and Myspace. During the span of the study, from October 2010 to April 2011, Facebook use increased by 75 percent while Myspace use decreased by 13 percent. The survey revealed that, on average, 34 percent of teens had at least one friend who posted about partying online, and 20 percent said their friends posted partying and drinking photos on social media sites.

Friends’ photos of smoking and drinking on Facebook and Myspace were found to strongly influence peers to engage in the same behaviors. What’s more, teens without close friends who drank alcohol were more likely to be affected by the increasing exposure to such online photos.

At the conclusion of the study, 30 percent of the survey respondents reported to have smoked, and more than half reported having had at least one drink of alcohol. Approximately one-third of the teens said that they had at least one friend who smoked and/or drank alcohol.

"The evidence suggests that friends' online behaviors are a viable source of peer influence," said Grace C. Huang, Ph.D., MPH, one of the study’s authors.

"Our study suggests that it may be beneficial to teach teens about the harmful effects of posting risky behaviors online and how those displays can hurt their friends.”

To talk to your child about social media, visit the American Academy of Pediatrics.