Although referring to horror movies as "bloodcurdling" might seem silly, Leidin University researchers have discovered that this process is exactly what happens when we watch scary movies; watching scary movies is associated with an increase in blood coagulant factor VIII, which is a blood clotting protein. The researchers believe that this process provides an important evolutionary benefit by preparing the body for blood loss during dangerous or life threatening situations, as outlined in the press release.

The term "bloodcurdling" originates back to medieval times and stems from the concept of feelings of fear or horror causing the blood to "curdle," but until now the theory has never been verified.

The scientists took 24 healthy volunteers ages 30 or younger and assigned them to various groups - fourteen were assigned to watch a scary movie followed by a non-frightening movie and 10 were assigned to watch these same movies in the reverse order. Each movie was approximately 90 minutes long and were viewed more than one week apart at the same time of day in a relaxed environment.

After taking blood samples within a fifteen-minute time period before and after each movie, the researchers found higher levels of coagulant factor VIII in participants both before and after the horror movie.

"The underlying biological mechanism of acute fear associated with an increase in coagulation activity is still to be unravelled," Banne Nemeth, first author of the study, told The Telegraph. "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."

The findings were published in the Dec. 16 issue of the British Medical Journal.