Fructus Ventris

I think it depends on the maturity of the teenager. Some teens are immature in a way that they will be disturbed and frightened by the images on the screen and react with fear, either open or, more likely suppressed. Others will be moved by the film, but will try to cover their emotions with bravado and maybe even contempt. And then there are the teens, probably the majority, who would react in the same manner that most adults would.

All in all, I think most teenagers could handle it, but I also think that theaters should strictly enforce the "must be accompanied by an adult" rule, and that those responsible adults will take the time necessary to process and talk about the film with the teen afterward.