Also known as folie à deux, shared psychotic disorder is relatively rare. It affects an otherwise healthy person who shares delusions with a close relative or friend. The dominant partner in a close relationship between a pair of relatives or domestic partners often suffers from schizophrenia or a similar disease. Over time, the less dominant partner begins to believe some or all aspects of the delusions afflicting the more dominant person.

A Close Relationship

The pair has often lived together for a long time with little or no social contact with others. Not many people seek treatment for their shared delusions, but when the primary partner is treated, the shared psychosis often fades away.

Sartre's Folie a Deux

French novelist and philosopher Jean Paul Sartre provides an account of a case of incipient folie à deux in “The Room”. In the story, Eve's husband, Pierre, suffers from a mental illness. It becomes apparent as the story progresses that Eve is getting very close to accepting Pierre's psychotic experiences as real.