Mrs. Clinton, a Democrat from New York, also called on industry leaders to create a uniform ratings system that would warn parents about sex and violence in video games, television and other forms of entertainment that children might be exposed to. By contrast, parents now look to a patchwork of ratings systems that differ from one sector of the industry to another.

At a forum held by the Kaiser Family Foundation, Mrs. Clinton cited studies indicating that children who are exposed to graphic images of violence display more aggressive behavior.

"It is a little frustrating when we have this data that demonstrates there is a clear public health connection between exposure to ...