A study of Americans' dreams in the weeks before and after Sept. 11, 2001, suggests that TV coverage of the terror attacks actually increased viewers' stress levels.

The finding probably applies to most major traumatic news stories, including this week's massacre of students and faculty at Virginia Tech, one expert said.

"Should we be allowing children to watch TV in the aftermath of this rampage in Virginia? Clearly, one of the lessons that we learned from September 11 is 'no' -- that parents should screen their kids, as well as themselves if they know themselves to be especially vulnerable -- from watching this," said Alan Hilfer, chief psychologist at Maimonides Medical Center in New York City.

Hilfer was not involved in the study, which was led by Ruth Propper, an associate professor of psychology at Merrimack College in North Andover, Mass.

Her team found that each additional hour of daily 9/11-linked TV viewing raised an individual's stress level by 6 percent, as reflected in dreams laden with grim images from that day's events.

But there was also some good news from the study -- stress levels began to decline the more people talked over the tragedy with family members and friends.

The study is published in the April issue of Psychological Science.

Widely publicized disasters will always engender stress, and Propper's team sought to understand the role today's 24-hour news cycle might play in that dynamic. To do so, the researchers focused on the content of "dream journals" kept by 14 Boston-area undergraduate students enrolled in a course on sleep and dreaming. The students began the journals starting at the end of August 2001, and kept them up until Dec. 3 of that year.

Propper said the relationship of dreams to daily stress levels is still being debated. "Some people think that dreams relieve or ease stress; others that dreams merely reflect processing that leads to decreased stress; and others think there is no relationship," she explained.

However, in this study, "we interpreted dreaming about specific references to 9/11 as indicative of stress," Propper said. In other words, dream imagery such as burning towers, crashing jetliners and the like were thought to indicate more stress than vaguer imagery not directly tied to 9/11.

The journals revealed that "the content of people's dreams changed after 9/11," Propper said. For example, compared to dreams occurring in the weeks before the event, "dreams after 9/11 were twice as likely to contain specific references to 9/11, to be threatening, or to contain themes related to 9/11," the researcher said.

But not every student had the same level of frightening 9/11 imagery in their dreams.

Specifically, participants who watched the most TV coverage of the attacks were also most likely to have dreams with high levels of explicit elements of 9/11, suggestive -- according to Propper -- of higher stress levels. In fact, the likelihood of this type of imagery rose with the number of hours per day that students watched 9/11 coverage (anywhere from one to 12 hours daily, according to student reports).

This research isn't unique, Propper noted. One study, published in 2003 in the journal Dreaming, yielded similar findings among 16 people who had kept dream diaries during the month before and after 9/11.

Propper said she doesn't know why repeat viewing of a horrific event might boost stress levels, or why so many people are fascinated by such coverage.

Hilfer believes the answer to the second question is simple -- curiosity.

"We are all looking for a kernel of new information, we are all looking to add to our base of information, even though it's traumatic for us," he said.

But based on the new findings, it may be healthier to switch off the TV once in a while, Hilfer said. "These are lessons that can be applied to media viewing for the incidents going on in Virginia right now," he added.

There may be one tried-and-true method of reducing anxiety linked to traumatic events: talking it over with others.

Propper's study found that 9/11-specific imagery in dreams was gradually replaced by less specific, less stressful images as people spent more time discussing the attacks with family or friends.

That finding made sense to Hilfer.

Psychologists "are always talking about people being able to share stress -- coming into therapists, talking about terribly stressful events in their own lives, and leaving saying, 'Gee, I feel better,' " he noted. "Nothing concrete may have been solved, but the act of sharing one's story and concerns -- having someone else be a listener to it -- often reduces stress."