At the origin of the term gaslighting is the 1944 movie Gaslight, the most famous adaptation of Patrick Hamilton’s eponymous 1938 play.7 Throughout the film, we see the protagonist questioning her own sanity as she seems to grow increasingly paranoid and forgetful.

The story starts with a murder: Alice Alquist, a famous opera singer, dies under mysterious circumstances in her own home; her killer is never caught. The film’s protagonist is the victim’s niece Paula (played by Ingrid Bergman), who was raised by her aunt and never knew her parents. After her aunt’s death, Paula moves to Italy to pursue a singing career of her own, but instead she falls in love with the pianist Gregory Anton (Charles Boyer). They get married after only a few weeks, and move back into Alice’s old London mansion. Apart from the bad memories the house evokes in Paula and her occasional forgetfulness, things seem to go well with the recently married couple at first. However, her forgetfulness gets worse. A picture is suddenly missing from the wall and she does not remember having moved it, yet everyone else denies having done so; she finds Gregory’s watch in her purse but cannot recall taking it; she loses an expensive brooch he had given her as a gift; and she hears noises and footsteps coming from the boarded-up attic; she even believes she can see the gaslights dim even though no one has touched.