In the first study to apply social network analysis methods to the examination of adolescent drug and alcohol use, researchers gathered evidence confirming long-held suspicions that Facebook and similar social media are highly influential to the teenage mind, the Daily Mail reports.

Thomas Valente, professor of preventive medicine at the University of Southern California and the study's principal investigator, surveyed 1,563 15 and 16-year old students on their online and offline friendship networks, including how frequently they used drugs and alcohol. He and his research team found a significant link between exposure to pictures of friends drinking and partying and their use of tobacco and alcohol use. Almost half of all participants reported visiting sites like Myspace and Facebook regularly.

"The evidence suggests that friends' online behaviors are a viable source of peer influence," Grace Huang, the study's first and corresponding author, told the Daily Mail. "This is important to know, given that 95 percent of 12 to 17-year olds in the United States access the Internet every day, and 80 percent of those youth use online social networking sites to communicate."

The research was conducted between October 2010 and February 2011, during which Facebook use increased by 75 percent and Myspace use decreased by 13 percent. On average, 34 percent of teens had at least one friend who talked about partying online, while 20 percent reported that they had friends who posted partying-related pictures. About one-third of the participants reported having at least one friend who drank or smoked.

A teen's frontal cortex, the part of the brain that controls reasoning and decision-making, is still not fully connected, according to Frances Jensen, a Harvard expert on epilepsy who has coped with the fluctuating moods of her own teenage boys.

"It's the part of the brain that says: 'Is this a good idea? What is the consequence of this action?'" Jensen said to NPR in March 2010. "It's not that they don't have a frontal lobe. And they can use it. But they're going to access it more slowly."

Teenage brains don't have the same amount of fatty matter (or myelin) as adults do, which allows for more freely-flowing neurological connections. In adolescence, research suggests that teens are far more prone to addiction, as their brain chemistry is especially responsive to their environment. This may give some clue as to why Facebook is such a powerful influence on the teenage brain, in addition to peer pressure in the strict social hiearchies of high school.

"If I want to go into a high school and change physical activity or other obesity behaviors, I have to understand there are cliques and subgroups of students that exhibit different risks," Valente said to ScienceDaily. "I would design different interventions for the different groups. We constantly are concerned about how ineffective our interventions are - this is a big reason why those interventions are not working. We can do a much better job promoting healthy behaviors if we understand the social network contexts and design these interventions with those cues in mind."

"Little is known about how social media use affects adolescent health behaviors," Huang, a post-doctoral fellow at the National Cancer Institute, said to the Daily Mail. "Our [latest] 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."