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DelusionalRelating to a fixed false belief held with total conviction despite evidence against it.Read more → disorder matters because it names a state where a person holds one delusionA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more →, or a tightly related set, for months while daily life otherwise continues largely unaffected. It is diagnosed when a single delusion, or a set of related delusions, persists for at least 3 months, without the prominent hallucinationsSeeing, hearing, or otherwise sensing things that are not really there.Read more → seen in schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more → (a psychotic illness with delusions, hallucinations and disorganised thinking). For example, imagine a man convinced his neighbour is stealing his post, who holds this belief unshakeably yet continues working and keeping most relationships normal. In practice, preserved day-to-day functioning outside the delusion's direct topic is a key clue pointing away from schizophrenia.

The delusionA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more →, or set of delusions, must last at least 3 months, with functioning otherwise preserved except where the belief itself directly interferes. Named subtypes describe the delusion's theme: persecutory (being harmed or conspired against), grandiose (inflated importance or talent) and somatic (a physical illness or defect). Two further subtypes are jealous, also called Othello syndromeA delusion of a partner's infidelity, held despite a lack of evidence.Read more → (belief a partner is unfaithful), and erotomanic, also called De Clérambault's syndrome (belief someone of higher status secretly loves the patient). Picture a woman utterly convinced a famous actor is secretly in love with her despite no contact ever occurring between them: that theme names the erotomanic subtype. In practice, naming the subtype by theme, not by severity, is exactly what the exam tests.

• A man holds an unshakeable belief that his wife is unfaithful, despite no evidence. Which risk most needs assessing?
• A woman is convinced that a well-known broadcaster she has not met is secretly in love with her. What is this called?
• A reclusive couple both express the same persecutory belief, but only one has a psychotic illness. What does the other most likely have?

• Schizophrenia, prominent hallucinationsSeeing, hearing, or otherwise sensing things that are not really there.Read more → and disorganised thinking, unlike delusionalRelating to a fixed false belief held with total conviction despite evidence against it.Read more → disorder's isolated, encapsulated delusionA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more →.
• The symptom 'delusion', a single fixed false belief that can appear in many conditions, whereas delusionalRelating to a fixed false belief held with total conviction despite evidence against it.Read more → disorder is a specific diagnosis requiring 3 months' persistence.
• Erotomanic (De Clérambault's) subtype, belief a higher-status person is in love with the patient, unlike the jealous (Othello) subtype's belief in partner infidelity.
• Delusional disorder, preserved functioning outside the delusion'sA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more → theme, rather than the broad functional decline typical of schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more →.

• Fire-setting is not the characteristic risk in delusionalRelating to a fixed false belief held with total conviction despite evidence against it.Read more → jealousy.
• Financial exploitation is a safeguarding concern in cognitive impairment rather than here.
• Capgras syndromeA delusion that a familiar person has been replaced by an identical impostor.Read more → is the belief that a familiar person has been replaced by an impostor.
• Fregoli syndromeA delusion that different people one meets are actually a single person in disguise.Read more → is the belief that strangers are a known person in disguise.
• Cotard syndrome involves nihilistic delusionsA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more → of being dead or having no organs.

• Extract the defining phenomenology, duration, severity and functional-impact clues.
• Match the pattern to the most specific diagnostic or assessment construct.
• Actively test the closest look-alike against the missing or contradictory clue.
• Choose the precise term rather than a broader category that is merely compatible.