*It means emotional manipulation – and dates from a pre-war play

THE term ‘gaslighting’ derives from Patrick Hamilton’s 1938 play Gas Light, which became the inspiration for the 1944 film Gaslight, starring Ingrid Bergman.

Her character’s husband manipulates her into thinking she has a mental illness by dimming the gas-fuelled lights at their home and telling her she is hallucinating. He then denies that the light changed when she points it out. Gaslighting is a form of emotional and psychological abuse in which a person or group makes someone question their sanity, perception of reality or memories. Victims often feel confused, anxious and unable to trust themselves. It is also a form of bullying and can be used to embarrass victims in front of others.

Gaslighting comes in many forms and includes using verbal abuse, minimising a victim’s worth and undermining someone.

It is a form of coercive control or a pattern of acts of assault, threats, humiliation and intimidation or other abuse that is used to harm, punish, or frighten their victim. Coercive control has been a criminal offence since 2015.