Can scary films literally curdle your blood?

According to a new study which has been carried out by researchers from The Netherlands, watching horror movies and feeling fear from them can raise the levels of a clotting protein known as blood coagulant factor VIII. In order to conduct the research, the team recruited 24 adults who were aged 30 or younger from Leiden University Medical Center.

It is important to note that all of the participants were healthy. 14 of them were randomly assigned to watch a scary movie that was followed by a non-scary, educational movie. The remaining 10 participants watched the same two movies but in the reverse order. Both films lasted about 90 minutes each.

The movies were watched for more than one week apart from one another but at the same time of the day. The environment was set up to make the participants feel comfortable and relaxed. The researchers had collected blood samples before and after each viewing to test for any increases or decreases in the clotting protein.

Blood samples of each volunteer were taken before and after each movie and were analyzed by scientists who searched for any clot formations. The participants also had to rate their levels of fear on a scale of 0 to 10, 10 being the worst fear they could ever experience.

According to Dr Nemeth it is: “Although it’s not immediately obvious by which means our results could confer clinical benefits a broader implication of these study results is that after centuries the term ‘bloodcurdling” in literature is justified. Of course there could be other factors taken into consideration when we link fear to blood clots, but concerning this particular study conducted on young, healthy adults, horror movies are literally blood-curdling but not blood-clotting. They found that levels of the protein were substantially raised in participants after watching the scary film, compared to levels after watching an educational film.

Back in the middle Ages, the term “curdle” developed from the idea that fear could “curdle” the blood or “run the blood cold,” but its validity had never been studied until now. Levels increased in 57 percent of the participants during the horror movie, but only 14 percent during the educational movie. Levels of coagulant also decreased in 86 percent of the participants during the educational movie, but only 43 percent during the horror movie. Interestingly, the team found no effect on other clot forming proteins from either movie, suggesting that coagulation may be triggered by acute fear, but this does not lead to actual clot formation.

“Levels increased in 12 (57 percent) participants during the horror movie, but only in 3 (14 percent) during the educational movie,” the team wrote. “Levels decreased in 18 (86 percent) participants during the educational movie, but only in 9 (43 percent) during the horror movie.” The researchers point out some study limitations, but ultimately conclude that “in young and healthy adults, watching bloodcurdling movies is associated with an increase in blood coagulant factor VIII without actual thrombin formation.” The study was published in The BMJ (British Medical Journal).