Psychological horror is a subgenre of both novels and films that uses the conventions, tropes, imagery, and plotlines of horror to explore topics surrounding mental and emotional health. Additionally, psychological horror aims to scare and unsettle audiences by employing macabre, grisly, and gruesome imagery to create a tone of suspense and anxiety. Erratic characters, unreliable narrators, and figures in acute psychological distress make frequent appearances and add to the drama of such narratives, and all of these factors characterize Margaret, the protagonist of The September House.

Within this framework, psychological horror uses fantastical and horror-based elements to explore darker, more deeply hidden aspects of the human psyche. The characters in these narratives therefore experience mistrust of others and of their own perceptions, along with feelings of paranoia, primal fear, suspicion, and anxiety. The dominant plot elements are often deliberately contradictory, creating an erratic reading experience that parallels the narrative arc of the characters. Misleading descriptions of hallucinations and delusions may cast doubt on the reality presented in the story, and authors often obscure which elements reflect real events and which suggest fabrications and indicate psychological disturbances.