1 Increase risk of bloody people
According to a study carried out by Dutch experts, scary and horror movies can increase the risk of blood clotting by fifth. Watching a horror movie can increase the clotting agent called Factor VIII in the but.
2 Increased heart rate and blood pressure
When a person gets scared, his heart rate and blood pressure rise. This could increase the risk of a heart attack.
3 Jacking off is increased
The production of the stress hormone, cortisol, is increased during scary situations and horror movies. Getting subjected to high levels of cortisol for prolonged periods of time can have many bad health effects.
4 Triggering repressed memories
Horror movies can result in recalling repressed fears and remembering scary events from childhood. When a person sees something frightening, his brain remembers all of the situations that caused a similar feeling.
5 It can cause phobias
A person can easily develop a phobia or get conditioned to learn a new fear, such as the fear of clowns, as a result of watching horror movies.
6 Can scare you for some time
Horror movies can scare a person for days, weeks or even months after watching them. The effect differs from one person to another. (See What are the body language signs of fear?)
7 Increase adrenaline levels
Horror movies can increase adrenaline levels for prolonged periods of time. This could have a bad health effect, as the body functions in the fight or flight mode.
8 Over-stimulate the nervous system
Very scary movies can over-stimulate the nervous system and cause mental exhaustion.
9 Trigger a depressive mood
Horror movies usually have many bad events. Many horror movies can trigger a negative or even a depressive mood, especially if the person already has problems with depression. (See How does it feel like to be depressed?)