Why do Gothic writers use madness/insanity as a topic?
Gothic writers have often appealed to topics such as insanity and madness as part of the stylistic licenses that are natural to the genre. Gothic literature is a darker branch of Romanticism that deals with cruel realism, the intervention of the supernatural, a dark and cold atmosphere, and the sense of nostalgia.
However, Gothic literature also involves inevitability, the loss of self-control, and fate as the ultimate determining factor in the character's lives. In this inevitability and loss of control, madness and insanity are topics that fit quite well. They are part of the process of losing control and they intensify the feeling of inevitability and despair that often come in the end of most of these stories as a shock factor.