NEW YORK (Reuters Health) - A comparative analysis of dream images suggests how deeply the September 11, 2001 attacks impacted Americans' emotions, researchers report.

Everyone experienced some sort of trauma, or at least emotional arousal by these events, Dr. Ernest Hartmann told Reuters Health. "We found, surprisingly, even dreams could pick this up," said Hartmann, of Tufts University School of Medicine in Boston, Massachusetts.

Hartmann and colleagues assessed the dreams of 11 men and 33 women living outside of Manhattan when the attacks occurred. The participants, who ranged in age from 22 to 70 years, had been recording their dreams for years, and none had relatives or friends who died in the attacks, the investigators note in the journal Sleep.

According to the results, post-9/11 dreams showed more intense images, which is "very consistent with findings in people who have experienced trauma of various kinds," Hartmann said in a statement. "The idea is that that we all experienced at least some trauma on 9/11."

The dreams after 9/11, however, did not contain more images of airplanes or tall buildings. Actually, none of the recorded dreams involved airplanes flying into towers or anything remotely close to that, even though all subjects had seen these images on TV.