Category: F20 F21 F22 F23 F24 F25 F28 F29
F24 — Induced delusional disorder: facilitator sheet
Teaching objective
The classification question F24 answers is: "has this person adopted a delusional belief mainly because of a close relationship with someone else who already holds it, rather than developing it independently?" F24 is fundamentally a relational classification: it cannot be assessed by looking at the induced person's belief in isolation — the relationship, the primary case, and the order in which the belief appeared are all part of the picture.
Choose material
Worked example · Case: A belief that arrived with a relationship · Case: A shared belief — but is it only shared? · Case: Two people, one belief, unclear order · Case: A belief older than the relationship
Worked example
Show scenario
Nadia, 33, has lived alone with her older sister Yasmin for the past three years, the two having become increasingly socially isolated from friends and other family over that time. Yasmin has for two years held a firm, detailed belief that a neighbourhood group is monitoring the sisters through their electricity meter, and has recently begun making the same claim herself, in very similar terms to Yasmin's. Nadia has no prior history of unusual beliefs, no hallucinations, and no odd speech or behaviour outside this one topic. When a caseworker temporarily arranges for Nadia to stay with a cousin for two weeks, her conviction noticeably softens.
Reveal step 1
Step 1 — Identify the relationship: the sisters are closely bonded and socially isolated together, the classic setting for induced delusional disorder.
Reveal step 2
Step 2 — Identify the primary case: Yasmin held the belief first, for longer, and in more elaborated detail — she is the primary case.
Reveal step 3
Step 3 — Check the induced partner's independent history: Nadia has no prior history of unusual beliefs and no broader psychotic features of her own.
Reveal step 4
Step 4 — Check the response to separation: Nadia's conviction softens when temporarily separated from Yasmin, a distinctive F24 feature.
Reveal step 5
Conclusion — F24 is best supported for Nadia: a delusion adopted mainly through a close relationship with an established primary case, softening on separation.
Comparison points
F24 is distinguished from F22 by origin, not content: F22's delusion arises independently in the person who holds it, while F24 requires that the belief was induced by a close relationship with a primary case who already held it, and typically softens on separation. F24 is distinguished from F20 in the induced partner by breadth and independence: the induced partner's picture is usually confined to the shared belief, without the broader independent disturbance (hallucinations, thought disorder, negative symptoms) that would support F20 in their own right — though the primary case may separately meet F20 or F22 criteria on their own.
Misconception prompt
Assessing a shared delusion in isolation, without asking about the relationship: "This person has a fixed false belief, so I should classify their delusion on its own merits."
Ask the class why this reasoning fails before revealing the explanation below.
Reveal why it fails
F24 exists precisely because a delusion cannot always be understood by looking at one person alone — some delusions are transmitted within a close, often socially isolated relationship. Skipping the relational question risks either missing an F24 pattern entirely (misclassifying the induced partner as an independent F22 case) or, less often, over-attributing an independently arising delusion to a relationship that had nothing to do with it.
Discussion prompts
Prompt 1
What single relational question is most decisive in identifying F24?
Prompt 2
Why can F24 not be assessed by looking at the induced person's belief in isolation?
Prompt 3
What commonly happens to the induced belief on separation, and why is this useful evidence?
Summary
A delusion adopted by one person mainly because of a close, often socially isolated relationship with a primary case who already holds the belief, typically softening on separation.