Category: F20 F21 F22 F23 F24 F25 F28 F29
F22 — Persistent delusional disorders: facilitator sheet
Teaching objective
The classification question F22 answers is: "is there one delusion, or a small set of related delusions, that has persisted for a substantial period, without the broader disturbance (characteristic hallucinations, thought disorder, negative symptoms) that would point to F20, and without it being induced by a close relationship with someone else who already holds the belief?" F22 is about the narrowness and persistence of the belief system, not its plausibility or its emotional intensity.
Choose material
Worked example · Case: One belief, two years, otherwise unremarkable · Case: A belief that arrived with a roommate · Case: Six weeks in, one fixed idea · Case: The picture broadens · Case: A dramatic belief, otherwise unremarkable · Case: Sorting the evidence — one belief, one household
Worked example
Show scenario
Elif, 47, has for the past two years been convinced that a coworker has been secretly recording her phone calls and forwarding them to her employer to have her fired. She describes this in detailed, internally consistent terms whenever it comes up, has changed her commute route and phone habits 'to be safe,' and has made a formal complaint to management, but otherwise continues to work full-time, maintains her friendships, and shows no unusual speech, affect, or behaviour outside this topic. She has never had hallucinations and no one else in her life shares the belief.
Reveal step 1
Step 1 — Check for a broader schizophrenic picture: no hallucinations, thought disorder, or negative symptoms are described; the disturbance is confined to one theme.
Reveal step 2
Step 2 — Check duration: the belief has persisted for two years, well past the three-month threshold.
Reveal step 3
Step 3 — Check whether the belief was induced by someone else: no one else shares it, so F24 does not apply.
Reveal step 4
Step 4 — Check functioning outside the theme: work, friendships, speech and affect are all preserved, consistent with a narrow delusional system rather than a broad disturbance.
Reveal step 5
Conclusion — F22 is best supported: one persistent, organised, non-bizarre delusion without a broader psychotic picture or evidence of induction from another person.
Comparison points
F22 is distinguished from F20 mainly by breadth: F22 is a narrow, single-theme (or closely related theme) delusional system without the characteristic hallucinations, thought disorder, or negative symptoms of F20. F22 is distinguished from F21 mainly by focus: F22 centres on one fixed, elaborated delusion, while F21 involves a more diffuse pattern of odd thinking, speech and relating without a single crystallised delusion. F22 is distinguished from F24 by origin: F22's delusion arises independently in the person who holds it, while F24 requires that the belief was induced by a close relationship with someone who already held it.
Misconception prompt
Treating any fixed false belief as automatically schizophrenia: "There's a fixed false belief here, so this must be schizophrenia."
Ask the class why this reasoning fails before revealing the explanation below.
Reveal why it fails
F20 and F22 both feature delusions, but they answer different classification questions. F22 exists precisely because a persistent, organised, single-theme delusion — even a dramatic or distressing one — is not, by itself, evidence of the broader disturbance F20 requires. Skipping this check leads to over-diagnosing schizophrenia in people whose presentation is actually much narrower.
Discussion prompts
Prompt 1
What is the single most important duration threshold for F22, and why does it matter?
Prompt 2
Name one feature that would make you reconsider F20 instead of F22.
Prompt 3
Explain why 'this belief could theoretically be true' is not the test that separates a delusion from an ordinary suspicion.
Summary
One persistent, often non-bizarre delusion or closely related delusional set, present for months to years, without the broader disturbance seen in schizophrenia.