Media negativity causes adult-level anxiety in children. Here is an unsurprising article in the Ottawa Sun:

http://www.ottawasun.com/Lifestyle/2006/03/02/1468946-sun.html

The article says:

"It's a very stressful time for kids to grow up." They feel threatened, vulnerable and more fearful of the future than ever before because of overexposure to pessimistic messages and images, says Mel Levine, pediatrics professor at the University of North Carolina Medical School and co-founder of All Kinds of Minds (Allkindsofminds.org).

"They're getting a warped view of the world. The media has developed a fascination with the downside of life" and it's dragging kids down too, says Levine. "There's no balanced view -- they're constantly taught to feel vulnerable instead of optimistic and excited about the future."

According to the Hospital for Sick Children psychiatrist Dr. Arlette Lefebvre, "We should let kids be kids and protect their innocence as long as possible."

I do believe this is true, and I think the constant negativity displayed by the liberal media in the last five years has had a similar effect on liberal adults in Philadelphia.