What structural element does the author use to establish the mental state of the narrator?

Gilman uses a Gothic touch to set us up for the narrator's morbid experience. She is literally imprisoned by her husband in an old house alone in a room. There is a constant sense of paranoia throughout the story which serves as a scaffold for the other elements of structure. The  narrator is paranoid about how her husband treats her, she is paranoid about the house, the room, and the wallpaper....Much of her nightmare takes place within the confines of her mind which is another gothic-like element.