Parents have been warning their children about the affects of peer pressure for decades now. However, the pressure teens today face on social media is a new phenomenon that parents largely don’t understand. New research is now showing that peer pressure via social media can be every bit as dangerous as the in-person kind.

A new study published today in the Journal of Adolescent Health has shown that teens who see their friends smoking and drinking on social media are more likely to pick up those vices themselves. Researchers from the University of Southern California surveyed more than 1,500 10th-graders from a Los Angeles-area high school back in 2010 and 2011. The students were asked about their smoking and drinking, as well as their social media use.

“Our study shows that adolescents can be influenced by their friends’ online pictures to smoke or drink alcohol,” said Thomas Valente, a co-author of the study and a professor of preventive medicine at USC. “To our knowledge, this is the first study to apply social network analysis methods to examine how teenagers’ activities on online social networking sites influence their smoking and alcohol use.”

The study found that students’ total number of online friends had no effect on their smoking or drinking habits. However, seeing pictures of their friends smoking or drinking on Facebook and Myspace was “significantly” associated with the teens’ own drinking and smoking. Another interesting observation seen in the study is that Myspace use, rather than Facebook use, was associated with more drinking.

“The evidence suggests that friends’ online behaviors are a viable source of peer influence,” said Grace Huang, lead author on the study. “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.”