Folie à plusieurs

This term describes a shared psychotic disorder - also known as "the madness of several."

Several people become swept up by a delusional idea, and this may have violent consequences in politics.

When this occurs in families, it is called 'folie en famille.'

Folie à plusieurs is a mass hysteria characterized by delusion. The line between mass hysteria and folie à plusieurs is not always very clear.

Reference:

1.) https://journals.sagepub.com/doi/abs/10.1177/0957154X08094236