Folie à Deux or delusion to two is a shared psychotic disorder where the patient manages to "convince" someone else of their own psychosis, although this second person does not present psychological disturbances.
The environmental factor determines the development of this disease, since it is necessary the intimate contact for Folie à deux to occur, although genetic factors may also be involved.
Close interpersonal relationships, lasting and socially isolated are the greatest risk factor for the development of this psychotic disease, and so the simple separation of the individuals involved is enough to cure the person induced to believe in psychosis.