If you watch a lot of scary movies, you probably already know that they can mess with your head. Depending on how scary that movie actually is, you may feel a bit uneasy for a few hours after you watch it. You may even have nightmares. The truth is, some people don’t really seem to get that scared when they watch a horror film and others are practically ready to jump out of their own skin. If you’re like most people, you land somewhere in the middle. You already know what these films can do to your mind but what about the impact they have on your body from a physical standpoint?

You might be surprised to learn that there is some research to suggest that watching a scary movie can make blood clotting more likely. If you think it sounds crazy that you could potentially get a blood clot from watching a horror flick, you’ll want to know that a study was published in a British medical journal linking the two. This study involved healthy individuals, none of whom were over the age of 30. A whopping 57 percent of the participants had a significant uptick in a blood protein called Factor VIII. This is the protein responsible for blood clotting. It’s thought that the increase in Factor VIII is tied directly to the fight-or-flight response people feel when they are frightened or feel threatened.

When you stop and think about it, all of this makes sense. The blood needs to clot when a person is injured. Therefore, it’s likely that this correlation between Factor VIII and fear is something that goes back eons. The problem occurs when you get scared because of a movie and there is no injury that needs to be addressed. In that scenario, your blood simply has a tendency to clot, something that could potentially cause you a lot of problems.

How serious can this actually be? Blood clots can cause a stroke or heart attack. In addition, they can hit one of the lungs, typically lodging in the main artery that goes from the heart to the lung itself. When this happens, it effectively prevents oxygenated blood from getting back to the heart, causing death.

Does this mean you should refrain from watching scary movies? If you’re generally healthy and you don’t scare easily, you just might be okay. Otherwise, it may be time to take stock of your current health and then decide for yourself.