New research looks at the impact of fear on coagulation factors in the blood.
Every Christmas, The BMJ publish a number of "special papers." Once a year, they open their hallowed pages to research of a more eccentric nature.
Despite the more curious choice of topics, each paper has been peer reviewed in their usual, meticulous manner.
The paper we will discuss here comes from Leiden University Medical Centre in the Netherlands and is titled "Bloodcurdling movies and measures of coagulation: fear factor crossover trial."
The term "bloodcurdling" first occured in print in the mid-20th century but has its roots in the 1800s. Merriam-Webster defines it as "arousing fright or horror."
The idea that fear physically affects the blood runs throughout Europe with a variety of similar phrases to be found in various countries.
In Germany, they have "das blut in den Adern erstarrt" (freezes the blood in your veins), in France, "à vous glacer le sang" (to freeze the blood) and "bloedstollend" (bloodcurdling) in the Netherlands.
The research team sets out their objectives:
"To assess whether, as has been hypothesized since medieval times, acute fear can curdle blood."
Why would fear curdle the blood?
At first glance, the theory might seem whimsical, but the premise has its basis in scientific fact. As an evolutionary adaptation, a coagulation response in preparation for an attack could be a beneficial adaptation. If the victim fears a physical wound, a quick clotting respond could be a life-saver.
A number of studies (one involving bungee jumpers) have shown that experiencing intense anxiety does appear to elevate levels of certain coagulation factors in the blood. However, these previous studies have involved patients with existing anxiety-based illnesses or people engaged in physical activities; in these individuals, there are other factors potentially influencing the make-up of the blood.
In contrast, the current study is the first to directly test changes in coagulation factors in healthy individuals experiencing fear in the absence of exercise.
Scary movie vs. documentary
To test their theory, the team took 24 healthy volunteers, (maximum age 30) and split them into two groups. The first group watched a scary movie, then, 1 week later, they watched a non-terrifying educational movie. The second group watched the films in the opposite order.
The scary movie in question was Insidious, where a family attempts to stop an evil spirit from trapping their comatose child. The non-frightening film was entitled A Year in Champagne, a behind-the-scenes documentary about making the famous drink.
Before and after each viewing, the participants filled out a questionnaire rating their fear levels and gave blood samples. The blood was tested for various coagulation "fear factors," including blood coagulant factor VIII, D-dimer, thrombin-antithrombin complexes and prothrombin.
The questionnaires demonstrated that the horror flick did indeed raise fear levels compared with the documentary. The results also showed that coagulant factor VIII was significantly higher after watching the frightening film than before.
The significance of coagulant factor VIII
Levels of coagulant factor VIII increased in 57% of the participants during the horror movie, but only in 14% of participants during the documentary. Levels decreased in 86% of participants during the educational movie but in only 43% during the horror movie.
Factor VIII is an essential blood-clotting protein that activates in response to injury. Defects in the gene that code for factor VIII lead to hemophilia; people with abnormally high levels of factor VIII have an increased risk of deep vein thrombosis and pulmonary embolism.
During the horror movie, coagulant factor VIII showed a mean increase of 11.1 IU/dL; this size of increase has the potential to be clinically significant. Previous studies have shown that an increase of just 10 IU/dL produces a 17% increase in the risk of venous thrombosis.
The researchers are quick to point out the study's limitations, namely its small sample size and the fact that the questionnaires were not validated. Despite these issues, the results certainly infer that when the human body is in a state of fear, there is a certain mobilization of clotting factors in the blood. The team ends on a festive note of caution:
"A truly relaxing and merry Christmas, without exposure to frightening situations, seems to be advisable to prevent venous thrombosis."
Medical News Today recently covered research into a groundbreaking probe that can detect blood clots anywhere in the body.