Harry, Meghan and the rise and fall of the folie à deux

I was interested to read that the next Joker film has the subtitle ‘Folie à Deux’ – a lovely phrase not used enough these days. When shrinks talk about folie à deux (also known as Lasègue-Falret Syndrome, after the 19th-century French psychiatrists who discovered it) they mean a ‘shared delusional disorder’ in which symptoms of an irrational belief are transmitted from one individual to another – including folie en famille or folie à plusieurs (‘madness of several’), sometimes leading to violence and even murder. But in popular culture, we generally mean a pair of lovers who act in such a way that anyone outside their set-up sees them as insane (‘folly of two’ or ‘madness shared by two’) and who provide a great deal of entertainment – and reassurance – for those who have chosen a tamer path.

FADs can involve psychopaths (Brady and Hindley, Bonnie and Clyde), doomed lovers (Sid and Nancy, Kurt and Courtney) or imminently antagonistic narcissists (Depp and Heard, Madonna and Penn), but they will share the sense of being the only two citizens of a state which is invisible to the rest of us, with its own language and rules.