For starters, before anyone freaks out, the U.S. Homeland Security threat level is actually just "Elevated" (yellow), though it's "High" for airplane flights. The threat level in NYC is "High" because we're just vigilant like that.

However, freaking out over things like threat levels is apparently bad for your health, according to a new study in the Archives of General Psychiatry. Over 2700 adults were studied to " examine the degree to which acute stress reactions to the 9/11 terrorist attacks predict cardiovascular outcomes in a national probability sample over the subsequent 3 years." And you know what? There was a 53% increase in reported physician-diagnosed cardiovascular ailments in the 3 years after September 11.

The Science Times examines the findings. During the study, the National Threat Advisory was "repeatedly raised," and even when the alert level would be lowered (from "high" to "elevated"), a third in the study said they were "personally worried about being victims of a terrorist attack, and that an attack is somewhat or very likely within several months." The study's lead author Alison Holman, UC Irvine, said, “It’s amazing how enduring these feelings of fear are, but look at what’s been going on. I’d be surprised if those terrorist alerts didn’t contribute in some way to the ongoing worry about terrorism in our sample.”

A NYU medical school professor, Dr. Marc Siegel, who has written about the "epidemic of fear," explained, "The fear response causes the heart to pump harder and faster, the nerves to fire more quickly. Excess triggering of this system of response causes the organs to wear down. For a person who is always on the alert, the result is a burned out body.” No wonder Rudy Giuliani looks so bad!

The Times' John Tierney has a chart showing how worried people are of a terrorist attack.