Final answer:
The development of a delusion in a patient who has a close relationship with another person with a psychotic disorder is called folie à deux, also known as shared psychosis.
Step-by-step explanation:
The development of a delusion in a patient who has a close relationship with another person with a psychotic disorder is called folie à deux, also known as shared psychosis.
This phenomenon occurs when a person starts to believe in the delusions of another person with a psychotic disorder, typically a family member or close friend. The individual without the primary psychotic disorder adopts the delusional beliefs and may even begin experiencing similar symptoms.
Shared psychosis is thought to be influenced by environmental and psychological factors. It is important to seek professional help for both individuals involved in this situation to ensure proper diagnosis, treatment, and support.