Classification & Assessment in Psychiatry · Paper A
Delusions (typology)
Getting the exact 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 → type right matters because exam vignettes reward the precise label, not just recognising that a belief is a delusion at all. Delusions are classified by their CONTENT, the theme of the false belief, separate from their form or origin. A patient who believes their organs have rotted away and that they are already dead has a nihilistic (Cotard) delusion, a content classically seen in severe depression. Naming the exact content type, rather than only labelling something 'a delusion', is what the exam actually tests.
Persecutory 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 → (being harmed or plotted against) are the commonest; grandiose delusions involve exalted status or ability, often in maniaA period of abnormally elevated mood, energy and activity, seen in bipolar disorder.Read more → (the elevated, overactive phase of bipolar disorder). Delusions of reference make neutral events feel personally significant; delusions of control (passivity) involve actions attributed to an external force, a first-rank symptom. Erotomanic delusions involve believing someone of higher status secretly loves the patient (e.g. a patient convinced a celebrity sends them coded signals of love through public appearances). Delusions of infidelity (Othello syndromeA delusion of a partner's infidelity, held despite a lack of evidence.Read more →) involve believing a partner is unfaithful on flimsy evidence, and can be dangerous. A patient who becomes convinced, without supporting evidence, that their partner is cheating, and threatens them over it, illustrates infidelity (Othello syndrome) delusions in practice. Exam vignettes expect the precise named type rather than a generic 'delusion', and infidelity delusions specifically carry a real risk of violence. Primary delusions arise suddenly and are not understood as arising from other mental events, unlike secondary delusions that develop from a mood or another belief. They are classified by mode of onset. An autochthonous delusion (delusionalRelating to a fixed false belief held with total conviction despite evidence against it.Read more → intuition) appears fully formed with no preceding trigger. Delusional perception attaches a new delusional meaning to a normal, correctly perceived object, and is itself a first-rank symptom of schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more →. Delusional memory retrospectively recasts a past event as though it had always carried delusional significance. Delusional atmosphere (delusional mood) is a pervasive sense that something ominous or significant is about to happen, and can precede and crystallise into a delusional perception. Erotomania is classically associated with delusional disorder, schizophrenia and mania, and erotomanic delusions are the most common delusional theme reported among stalkers.
Two can share the same underlying mechanism yet lead an exam question, and a real clinical risk assessment, in completely different directions depending on their CONTENT. A patient who believes their neighbour is spying on them and a patient who believes they are secretly a reincarnated monarch are both deluded, but only one of those beliefs typically carries a direct risk of violence toward another named person. This is why psychiatry classifies delusions by theme: persecutory, grandiose, nihilistic, referential, control, erotomanic, infidelity, and hypochondriacal, rather than treating "delusion" as a single undifferentiated category.
A delusion, again, is a fixed false belief held with complete conviction, not explained by the person's culture, and resistant to contrary evidence. "Delusion type" simply means WHAT the false belief is about: its theme or subject matter, completely separate from HOW it arose (that question is answered by the primary/secondary split covered elsewhere).
The most commonly missed content type is of infidelity, sometimes called , because on the surface it can sound like ordinary, if intense, jealousy. For example, imagine a patient who becomes convinced, without any supporting evidence, that their partner is cheating, and begins searching their phone and threatening them over it. That is not simply jealousy: it is a delusion, and it carries a genuine, well-documented risk of violence toward the partner, which is why it is flagged separately from the other content types on any risk assessment.
content tends to track the person's underlying emotional state or illness, even though the itself is not "logical." In depression, the prevailing emotional tone is worthlessness and hopelessness, so delusions there skew toward nihilistic (Cotard, believing one is dead, rotting, or does not exist) or hypochondriacal (believing one has a serious illness despite evidence otherwise) themes. In , the prevailing tone is inflated self-worth, so delusions skew grandiose (exalted status, special powers, or a special mission). In paranoid states, the prevailing tone is threat, so delusions skew persecutory (being harmed, followed, or plotted against). Recognising this link between mood and content is often the fastest route to the correct diagnosis in a vignette.
Persecutory delusions (the commonest type overall) involve a belief of being harmed, followed, or conspired against. Grandiose delusions involve exalted status, wealth, identity, or ability, and are classically seen in . Nihilistic (Cotard) delusions involve believing one is dead, does not exist, or that one's organs have rotted away, and are classically seen in severe depression. Delusions of reference make neutral, everyday events (a stranger's cough, a television broadcast) feel personally and specifically significant. Delusions of control, also called passivity delusions, involve actions, impulses, or feelings attributed to an external force controlling the person: this is also a first-rank symptom of . Erotomanic delusions (de Clérambault's syndrome) involve believing someone of higher status secretly loves the patient. Delusions of infidelity involve believing a partner is unfaithful on flimsy or no evidence. Hypochondriacal delusions involve a fixed, false conviction of having a serious physical illness, which persists even after full medical reassurance and normal test results.
As with any , there is no laboratory test; the content type is established purely through careful, non-leading interviewing that lets the patient describe the belief in their own words, followed by direct, gentle questioning about the theme (harm, status, health, a partner's fidelity, or a specific admirer). Clinicians specifically ask about delusions of infidelity and persecutory content because both carry a measurable risk of violence toward a named third party, which must be documented in any formal risk assessment alongside the diagnosis itself.
Management is directed at the underlying illness generating the , following the same NICE pathways as for delusions generally: NICE CG178 for psychosis and (antipsychotic medication plus cognitive behavioural therapy for psychosis), and NICE NG222 for psychotic depression (antidepressant with an added antipsychotic, or for severe presentations), with the Maudsley Prescribing Guidelines used for the practical drug and dose detail. Where the delusion names a specific, identifiable target, as in infidelity or persecutory delusions naming a real person, safeguarding and risk-management steps for that named individual are taken alongside starting treatment, since medication alone may take weeks to reduce conviction in the belief.
Exam vignettes deliberately give a specific content clue and expect the precise label, not a generic "" answer. A stranger on television sending secret personal messages is a delusion of reference, not a persecutory delusion, because the theme is significance rather than threat. Infidelity delusions are the classic "don't just call it jealousy" trap, because they carry a distinct violence risk the exam wants you to flag.
Match every content to its exact named type: persecutory, grandiose, nihilistic, referential, control, erotomanic, infidelity, or hypochondriacal, because the theme both hints at the underlying mood disorder and, for infidelity and persecutory delusions specifically, signals a real risk to a named other person.