The next time you go on a movie night, you might want to consider your choice of film as emerging evidence suggests that horror films can actually cause "bloodcurdling." It is a term coined during the medieval times based on the idea that fear would cause blood to run or curdle. This is the first study to check whether the old saying has some scientific basis.

In relation to this, researchers found that horror films can actually increase the production of blood clotting protein called Factor VIII. The study involved 24 participants who are 30 years old or below. Randomly assigned in two groups, the first one with 14 members was tasked to watch a scary film, the 2010 supernatural horror film "Insidious" and then followed by a non-frightening educational movie, while the other group did the vice versa.

Blood samples were obtained and analyzed before and after each 90 minute long movie that was shown at the same time of the day with more than a week gap. Results revealed that Factor VIII levels indeed increased at an average of 11 IU/dl. And this level has been associated with increased risk for blood clot. 

While watching an educational film titled "A Year In Champagne," increase of blood clot agent was manifested by three participants (14 percent) but seeing horror films is fourfold higher. In addition, study participants were asked to guage their fear between 0 (no fear at all) and 10 (worst fear imaginable). They were also asked whether they have seen the movie and general questions about lifestyle and movie genre choices. Tallies revealed that with an average difference of 5.4 points, horror movies are perceived scary than educational videos.

But with regard to other clotting factors, no significant difference were found. This implies that even if acute fear triggers coagulation, it is unlikely to result to clot formation.

"In young and healthy adults, watching bloodcurling movies is associated with an increase in blood coagulant factor VIII without actual thrombin formation," researcher Dr. Banne Nemeth said.