Audiences weren't ready for The Exorcist when it was released in 1973. The film was insanely horrific for the time period and it was so intense that people went crazy in movie theaters. Even the first trailer for the film that was released was considered so jacked up that it ended up being pulled from theaters and banned. The combination of terrifying visuals and the unsettling musical score was so intense that there are reports of people actually vomiting during it.
The trailer plays out like a disturbing nightmare and even though I've seen the film multiple times this trailer still affected me and creeped me the hell out! Just wait until you watch it and see. I will say the best viewing experience comes with the volume turned up and the lights out.
I love trailers like this that invoke emotions within us. These kinds of trailers are so much better than trailers that lay out the entire plot of the film.