Last week, The New York Times reported that CIA interrogators subjected 9/11 plotter Khalid Shaikh Mohammed and Al Qaeda operative Abu Zubaydah to a total of 266 episodes of waterboarding between 2002 and 2003. More recently news broke that top Bush administration officials, including Condoleezza Rice and John Ashcroft, had condoned the practice as early as 2002.

The Obama Administration considers waterboarding—in which a person is strapped on a board with a rag or cloth covering his or her face and doused with water—a form of torture. So does the United Nations’ former High Commissioner for Human Rights, Louise Arbour, according to news reports.

It seems pretty obvious that waterboarding can cause emotional trauma, but does it threaten a person's physical health?

No doubt about it, says Allen Keller, an associate professor of medicine at New York University School of Medicine (who, it should be noted, testified that waterboarding is a form of torture before the Senate Select Committee on Intelligence in 2007). During waterboarding, some of this water can flow through the nostrils and into the lungs, Keller explains. Water in the lungs, especially if it's dirty, can cause potentially deadly pneumonia or pleuritis, an inflammation of the lung lining.

Waterboarding could also cause hypoxia, a condition in which the body is not getting enough oxygen, either because the victim is holding his or her breath or inhaling water—and inadequate oxygen supplies can lead to deadly organ failure, Keller adds.

But don’t underestimate how tightly intertwined the physical and psychological experiences of waterboarding are, Keller notes. Since it mimics the terrifying sensation of drowning, it triggers the release of stress hormones called catecholamines that can cause heart rate and blood pressure to soar, potentially setting the stage for heart attack in a person with underlying heart disease, he says.

But even healthy people can die from sheer terror, as Martin A. Samuels, chairman of the neurology department at Brigham and Women’s Hospital in Boston told earlier this year. The sudden outpouring of stress hormones can cause the heart to beat abnormally, hampering its ability to deliver blood to the body.

Waterboarding might be an ideal way to cause a fear-induced heart problem, Samuels speculates, pointing to experiments by the late Johns Hopkins psychobiologist Curt Richter, who in the 1950s created what he called a “swimming” jar for wild rats that was partially filled with water, allowing them to swim but not escape. The rats often died, and when Richter examined their hearts, he found damage suggesting stress hormones caused heart muscle cells to contract uncontrollably, Samuels explains.

“Make no mistake about it, [waterboarding] is a profoundly traumatic event,” Keller says. “The physical and psychological and social aspects are all interdependent and feed off one another.”