Researcher Aryn Karpinski of Ohio State University's education department said surveys completed by 219 U.S. undergraduates and graduates found that those who used Facebook achieved lower grades, The Sunday Times of London reported.
"Our study shows people who spend more time on Facebook spend less time studying," Karpinski said. "Every generation has its distractions, but I think Facebook is a unique phenomenon. It is the equivalent of the difference between getting an A and a B."
Facebook allows users to chat, take quizzes, post comments and search for new or old friends.
Karpinski also found that 79 percent of study respondents who admitted to Facebook usage felt such online activities did not impact their studies, The Times said.
No margin of error was given for Karpinski's study.