
Gaslighting is distinct from genuine relationship conflict in that one party manipulates the perceptions of the other. Over time, the listening partner may exhibit symptoms often associated with anxiety disorders, depression, or low self-esteem. Gaslighting typically occurs over a long duration and not on a one-off basis.

Merriam-Webster defines it as " psychological manipulation" to make someone question their "perception of reality" leading to "dependence on the perpetrator". Largely an obscure or esoteric term until gaining traction in the mid-2010s – The Times only used it nine additional times in the following 20 years – it has broadly seeped into the English lexicon since, and is now used more generally. According to the American Psychological Association in 2021, gaslighting "once referred to manipulation so extreme as to induce mental illness or to justify commitment of the gaslighted person to a psychiatric institution".

The gerund form gaslighting was first used in the 1950s, particularly in the episode of The Burns and Allen Show in The New York Times, it was first used in a 1995 column by Maureen Dowd. The term "gaslighting" itself is neither in the screenplay nor mentioned in either the films or the play in any context. In the story the husband secretly dims and brightens the indoor gas-powered lighting but insists his wife is imagining it, making her think she is going insane. Set among London's elite during the Victorian era, it portrays a seemingly genteel husband using lies and manipulation to isolate his heiress wife and persuade her that she is mentally unwell so that he can steal from her. The term alludes to the 1944 American film Gaslight, a remake of the 1940 British film of the same name, which in turn is based on the 1938 thriller play Gas Light. Charles Boyer, Ingrid Bergman, and Joseph Cotten in the film Gaslight (1944)
