Through the movie the characters are naked.

A man and a woman are attached to each other with stitches. The wound resulted from the procedure can be seen a couple of times.

A man is shot on his leg. With some blood visible.

There are swear words.

There is alcohol and drugs.

The whole concept of two people attached together might be intense for some viewers.

Although the movie doesn't have too much gore, the very nature of its plot can be tense. Which relies more on being more psychological than anything else.