Frightened? Your Blood Really Is Curdling

[Riddick]

Just watching a scary movie is enough to trigger the release of blood-congealing proteins, a surprising phenomenon recently documented by Dutch physicians Banne Nemeth and Luuk J.J. Scheres, who specialize in the treatment of blood clots at Leiden University Medical Center in the Netherlands.

The doctors were inspired to test whether fear thickens the blood after they spotted a collection called “Bloodcurdling Tales of Horror and Macabre” by H.P. Lovecraft at a local bookstore.

“Venous thrombosis issues are always in the back of my mind,” Dr. Scheres said, using the medical term for blood clots. “I thought this is a good thing to prove. Is it actually bloodcurdling?”

The doctors realized a version of the word “bloodcurdling” exists in multiple languages. In Dutch, it’s “bloedstollend.” The French say “à vous glacer le sang,” or blood-chilling. The Germans express it as “das Blut in den Adern erstarrt,” meaning the blood in the veins solidifies.

They also found literary references depicting the experience as far back as Virgil’s Aeneid, the epic poem written between 30 and 19 B.C., which includes a description of icebound veins.

Choosing a scary movie for test subjects to view was easy. The doctors relied on the advice of a friend fond of the genre who said “Insidious,” a 2010 film about a comatose child who is possessed by evil spirits, was scary enough to make viewers’ blood run cold.

Finding a film that wouldn’t trigger such a chilling response proved more challenging. They went with “A Year in Champagne,” a rather dull movie about French winemaking. (Sorry, France.)

Only the horror movie showed a distinct increase in Factor VIII, a protein that activates coagulation. The doctors believe there may be an evolutionary explanation for the response: Acute fear, they suspect, activates the coagulation system to prepare the body for potential blood loss during life-threatening situations.

The doctors, no fans of fright, plan no further studies. After all, watching horror movies is bloodcurdling. But dealing with deep-vein thrombosis or pulmonary embolism—that’s just another day at the office.

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