PHILADELPHIA - Depictions of explicit and graphic suicides in movies tripled from 1950 to 2006, according to an analysis of top-grossing films.

The report, by the Annenberg Public Policy Center at the University of Pennsylvania, was published in the August issue of Archives of Suicide Research. It found no difference between PG-13- and R-rated films in the most explicit portrayals of suicide.

Lead author Patrick E. Jamieson said that although it's impossible to establish a causal connection, the tripling of U.S. teen suicide since 1960 has coincided with the increase in movie suicide portrayals. The results, based on an analysis of 855 top-grossing films and released Tuesday, indicate the need for further study of the effects of movie suicides on adolescent audiences, the authors concluded.

"We know as well that exposure to movie-portrayed suicide correlates with thinking that one cannot get effective treatment for mental health problems," Jamieson said. "There is something seriously wrong with a movie ratings system that attaches a PG-13 rating to a movie containing explicit, graphic modeling of suicide."

A Motion Picture Association of America rating of PG-13 means special parental guidance is strongly suggested for children under 13 and some material may be inappropriate for young children. An R rating means viewing is restricted and anyone under age 17 requires an accompanying parent or adult guardian.

The researchers looked at the top 30 movies in the U.S. each year from 1950 from 2006. From the 855 that had suicide references, they set up a suicide explicitness scale and weighed the portrayals in each movie based on how much or little of a suicide was merely suggested or was graphically shown.

From 1968 to 1984, movies rated R by the Motion Picture Association of America had five times more highly explicit suicide behavior portrayals than those rated G (general audiences) and PG (parental guidance suggested). The category PG-13 was instituted in 1985, but the report found PG-13 and R films became indistinguishable when it comes to depictions of suicides.

An MPAA spokesman did not immediately respond to an Associated Press request seeking comment Tuesday evening.