Psychological thriller is a fictional thriller story which emphasizes the psychology of its characters and their unstable emotional states. In terms of classification, the category is a sub-genre of the broader ranging thriller category, with similarities to Gothic and detective fiction in the sense of sometimes having a "dissolving sense of reality", moral ambiguity, and complex and tortured relationships between obsessive and pathological characters. Psychological thrillers often incorporate elements of mystery, drama, and horror, particularly psychological horror. They are usually books or films.