How does the author use the setting to mirror the narrators mental state?

The changing images in the wallpaper personify the narrator's increasing mental anguish. The old nursery room becomes a literal and figurative prison for the narrator. The more she loses herself in the wallpaper the more detached from reality the narrator becomes. The narrator begins to relate to the woman trapped in the wallpaper until she actually becomes that woman struggling to get out of her prison.