One of the true story elements could be the general idea of a house with a dark past. There are many real - life old houses that are rumored to have had tragic events occur within them, and Hill House is based on this concept.
There are several true story elements in 'The Haunting of Hill House'. Firstly, the location - based horror aspect. There are real places in the world where people claim to have had spooky experiences, and Hill House is set up in a similar way, isolated and with a history of misfortune. Secondly, the psychological impact on the people who live in or visit the house. In real - life cases, people who enter supposedly haunted places often experience stress, fear, and psychological changes. The characters in the story also go through these, with their mental states deteriorating as they stay in the house. Thirdly, the idea of objects in the house being 'haunted' or having a strange energy. In real - life paranormal investigations, there are often reports of certain items in a haunted location being associated with unusual activities, and this is also seen in the story, for example, with some of the old furniture or artifacts in Hill House.
The sense of unease and unexplained phenomena in the story might be based on true accounts. In real - life paranormal experiences, people often report feeling a strange presence, hearing noises, or seeing things that can't be easily explained. 'The Haunting of Hill House' incorporates these types of experiences, like the characters hearing unexplained whispers or seeing shadowy figures. Also, the idea of a house having a sort of 'personality' or being 'alive' in a malevolent way is something that has been reported in some real - haunted - house stories.