I'm not certain, but I believe there is substantial research done in Canada connecting the continual display of violence in movies and television with an increase in violent acts by kids and teens who have watched a large amount of TV.

That's apparently why Canadian film ratings are different than US ones (a film rated PG here might get an the equivalent of an R in Canada if it is violent, while a film rated R here because of near-explicit sexual content might get the equivalent of a PG in Canada.

If the research is actually solid and well conducted, then it wouldn't be a big step to say that we could probably generalize the findings about that to depictions of sexual behavior.

Again, I haven't read the research, this is just what I've been told secondhand.