(CBS) -The songs may change, but one theme remains the same: Popular songs often portray alcohol and drug use in a positive light. The latest study of the issue comes in an analysis of the 279 most popular songs of 2005 by Brian A. Primack, M.D., and colleagues at the University of Pittsburgh. A third of the songs portrayed alcohol and drug use. And more than two-thirds of these portrayals were positive, the researchers found.

“Previous research has shown that exposure to substance-use messages in media is linked to actual substance use in adolescents,” Primack says in a news release.