Other psychotic disorders: schizotypal disorder, persistent delusional disorders, acute and transient psychotic disorders, and schizoaffective disorder. Clinical features, course, and treatment
The psychotic disorders that sit beside schizophrenia in ICD-10's F2 block, schizotypal disorder, the persistent delusional disorders, the acute and transient psychotic disorders and schizoaffective disorder, with induced delusional disorder (folie à deux); how each is recognised and told apart, how ICD-11 and DSM-5 have regrouped them, and their course and treatment.
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- Checked 26 Oct 2026
Contents6 sections
At a glance
- Beside schizophrenia, ICD-10's F2 block holds schizotypal disorder, the persistent delusional disorders, the acute and transient psychotic disorders, induced delusional disorder and schizoaffective disorder. Each is told apart by its symptoms and, above all, by its time course.
- Schizotypal disorder is a lasting pattern of eccentricity, odd beliefs, unusual perceptions, suspiciousness and social anxiety without sustained psychosis. ICD-10 and ICD-11 keep it with schizophrenia; DSM-5 calls it a personality disorder.
- A persistent delusional disorder is one fixed, circumscribed delusion or set of delusions lasting at least three months, in a person who otherwise thinks and functions well. Persecutory delusions are the commonest; jealous and erotomanic delusions carry a risk to the person they are about.
- An acute and transient psychotic disorder starts within two weeks, often after stress, and resolves within one to three months. ICD-11 keeps only the polymorphic form, with rapidly changing symptoms.
- In schizoaffective disorder, schizophrenic symptoms and a manic, mixed or depressive episode are equally prominent in the same episode; its outlook lies between schizophrenia and mood disorders.
- Antipsychotics are the main drug treatment, with a mood stabiliser or antidepressant in schizoaffective disorder. A delusional patient is engaged without arguing or colluding, and in folie à deux the healthier partner often recovers once separated.
Definition and overview
The other psychotic disorders share psychotic symptoms with schizophrenia but differ from it in the range of symptoms, their duration, or how they are mixed with mood disturbance. They matter because they are often mistaken for schizophrenia, because some evolve into it, and because their treatment and outlook differ.
| ICD-10 | ICD-11 | DSM-5-TR |
|---|---|---|
| F21 Schizotypal disorder | Schizotypal disorder, still among the primary psychotic disorders | Schizotypal personality disorder (cluster A), cross-listed with the schizophrenia spectrum |
| F22 Persistent delusional disorders, at least 3 months | Delusional disorder, at least 3 months | Delusional disorder, at least 1 month, with a specifier for bizarre content |
| F23 Acute and transient psychotic disorders, four subtypes | Acute and transient psychotic disorder, the polymorphic form only | Brief psychotic disorder (1 day to under 1 month), schizophreniform disorder (1 to 6 months) |
| F24 Induced delusional disorder | no category of its own; indexed under delusional disorder, unspecified | Other specified psychotic disorder (delusional symptoms in the context of a relationship with someone with prominent delusions) |
| F25 Schizoaffective disorder: manic, depressive, mixed types | Schizoaffective disorder, both sets of symptoms within the same episode for at least a month | Schizoaffective disorder: bipolar and depressive types; the mood episode present for most of the illness |
Etiology and pathophysiology
Schizotypal disorder
It is seen as a partial expression of the genetic liability to schizophrenia: it is commoner in the relatives of people with schizophrenia, and their relatives in turn have a raised risk of schizophrenia. Childhood adversity adds to the risk.
Persistent delusional disorders
The cause is unknown, and delusions can arise from many brain, medical and drug-related illnesses, so these are always sought. The risk rises with older age, social isolation, migration, deafness and other sensory loss, low income, paranoid or sensitive personality traits, a family history of paranoid disorders, and brain injury. Cognitive accounts point to jumping to conclusions on too little evidence, blaming others for bad events to protect a fragile self-esteem, and explaining an unusual experience with a belief that then becomes fixed.
Acute and transient psychotic disorders
Many follow an acute stressor such as a bereavement, migration, imprisonment or childbirth, and they are commoner in women and in low- and middle-income countries. Older European concepts survive within them: the bouffée délirante of French psychiatry, the cycloid psychoses of the German school and the reactive psychoses of Scandinavia.
Schizoaffective disorder
Families with schizoaffective disorder carry the genetic risks of both schizophrenia and bipolar disorder, which supports the view that psychosis and mood disorder lie on a continuum rather than being two separate diseases.
Induced delusional disorder
Two or occasionally more people in a close, emotionally dependent relationship, usually socially isolated (spouses, siblings, a parent and child), come to share a delusion. The primary partner, often the dominant one, has a psychotic disorder; the secondary partner, often more dependent, less intelligent or physically ill, takes it on.
Clinical features
Schizotypal disorder
ICD-10 asks for three or four of these (four in its research criteria), present continuously or episodically for at least two years, without ever meeting the criteria for schizophrenia:
- cold or inappropriate affect; odd, eccentric behaviour or appearance;
- poor rapport and social withdrawal;
- odd beliefs or magical thinking (telepathy, a sixth sense) that shape behaviour;
- suspiciousness or paranoid ideas;
- obsessive ruminations without inner resistance, often about the body, sex or aggression;
- unusual perceptions, including bodily illusions, depersonalisation and derealisation;
- vague, circumstantial, metaphorical, overelaborate or stereotyped thinking and odd speech;
- occasional brief quasi-psychotic episodes with illusions, hallucinations and delusion-like ideas.
Persistent delusional disorders
The delusion is fixed, organised and usually plausible, and the rest of the mental state is largely normal: no persistent hallucinations (brief tactile or olfactory ones linked to the delusion are allowed), no schizophrenic symptoms such as thought interference or thought disorder, no lasting mood disorder, and the affect, speech and behaviour are appropriate to the delusion. Patients often present to other doctors, lawyers or the police rather than to psychiatrists.
| Type | The belief | Risk and pointers |
|---|---|---|
| Persecutory, the commonest | being conspired against, cheated, spied on, poisoned or obstructed | complaints and lawsuits; the litigious or querulant form fills courts and complaint systems; violence against supposed persecutors |
| Jealous (morbid or Othello jealousy) | the partner is unfaithful | checking phones, underwear and whereabouts; commoner in men, often with alcohol; a recognised cause of violence and homicide against the partner |
| Erotomanic (de Clérambault syndrome) | someone, usually of higher status, is secretly in love with the patient | commoner in women in clinical samples; letters, calls and stalking; harassment of the object or of a supposed rival |
| Grandiose | special talents, discoveries, identity or relationships | approaches to famous people, ruinous projects |
| Somatic (hypochondriacal) | infestation (delusional parasitosis), a foul smell (olfactory reference), a deformity, a disease | often seen by dermatologists, surgeons and physicians; skin damage from picking; suicide |
| Self-referential, mixed | being talked about or watched; more than one theme |
Delusions are told from overvalued ideas by their fixity, how they arose and how they rule behaviour, and from beliefs shared by the person's culture or religion. Late paraphrenia, persecutory delusions with hallucinations in older people, often with deafness and isolation, is related.
Acute and transient psychotic disorders
The psychosis appears within two weeks of the first change, often abruptly within 48 hours, and full recovery usually follows within two to three months.
| ICD-10 subtype | Features | Reclassified when |
|---|---|---|
| Acute polymorphic, without symptoms of schizophrenia | hallucinations, delusions and perceptual disturbance that change from day to day or hour to hour; emotional turmoil, perplexity, confusion without disorientation | |
| Acute polymorphic, with symptoms of schizophrenia | as above, with schizophrenic symptoms | schizophrenic symptoms last over a month: schizophrenia |
| Acute schizophrenia-like | stable schizophrenic symptoms without the polymorphic picture | they last over a month: schizophrenia |
| Other acute predominantly delusional | fairly stable delusions or hallucinations | delusions last over 3 months: persistent delusional disorder |
Each can be coded with or without an acute stress in the two weeks before onset; DSM-5-TR also marks an onset in pregnancy or within four weeks of childbirth.
Schizoaffective disorder
Definite schizophrenic symptoms, such as thought interference, passivity, third-person or commenting voices or bizarre delusions, occur with a definite manic, mixed or depressive episode, both prominent, at the same time or within a few days of each other in the same episode. The manic type tends to be florid and acute, often with full recovery; the depressive type is often less dramatic but more chronic. It is not diagnosed when psychotic symptoms only appear within a mood episode and match the mood (a mood disorder with psychotic features), or when depression follows schizophrenia (post-schizophrenic depression).
Induced delusional disorder
The secondary partner holds the same delusion as the primary partner, usually persecutory or about illness, infestation or religion, and would not otherwise be psychotic; the belief often fades once they are apart.
Telling them apart
| Schizotypal | Delusional disorder | Acute and transient | Schizoaffective | Schizophrenia | |
|---|---|---|---|---|---|
| Onset | adolescence, lifelong | middle or late adult life, gradual | within 2 weeks, often after stress | young adult, often acute | late teens to thirties |
| Time criterion (ICD) | 2 years | 3 months | resolves in 1 to 3 months | the same episode, 1 month in ICD-11 | 1 month |
| Psychosis | brief and quasi-psychotic only | a circumscribed delusion | florid, often changing | full schizophrenic symptoms | full schizophrenic symptoms |
| Mood episode | no | no lasting one | brief swings | yes, equally prominent | not dominant |
| Functioning | eccentric, isolated | mostly preserved | returns to baseline | variable between episodes | often declines |
Point at a name or a part to light it.
The other psychotic disorders differ from schizophrenia, and from one another, in how they come on and how long they last. Schizotypal disorder is lifelong eccentricity with only brief quasi-psychotic spells; a delusional disorder is one delusion lasting at least 3 months, with life otherwise kept going; an acute and transient psychosis comes on within 2 weeks, often after a stress, and clears within a few months; and in schizoaffective disorder psychotic symptoms and a mood episode come together in the same episode.
Simplified: the heights have no scale; up the lane is more psychotic symptoms; each lane is a typical course drawn by hand, not one patient's, and each disorder varies widely; schizophrenia itself, against which these are told apart, has its own topic.
3 sources
- World Health Organization. The ICD-10 Classification of Mental and Behavioural Disorders: Clinical Descriptions and Diagnostic Guidelines. WHO, 1992. F21 to F25.
- World Health Organization. Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural and Neurodevelopmental Disorders (CDDR). WHO, 2024. Schizophrenia or other primary psychotic disorders, 6A20 to 6A2Z.
- Semple D, Smyth R. Oxford Handbook of Psychiatry, 4th edition. Oxford University Press, 2019. Chapter 5, Schizophrenia and related psychoses.
Diagnosis and management
All of them need the same exclusions as schizophrenia: a history from others, a mental state examination with a risk assessment, a physical and neurological examination, blood tests, a urine drug screen and brain imaging when the onset is late or there are neurological or cognitive signs. Delirium, dementia, epilepsy, encephalitis, drugs and substance use come first. A first episode of any of these psychoses is referred to an early intervention in psychosis service.
Schizotypal disorder
Care is mostly psychological and practical: a supportive, consistent relationship, CBT for anxiety and odd beliefs, social skills training and help with work. A low dose of an antipsychotic, such as risperidone up to about 2 mg, can help quasi-psychotic symptoms and suspiciousness, with some trial evidence. Depression and social anxiety are common and treated in their own right, and the patient is watched for transition to schizophrenia. The main differentials are schizoid, paranoid and other personality disorders, autism and a schizophrenic prodrome.
Persistent delusional disorders
- 1
Engage
Patients rarely see themselves as ill. The clinician neither argues against the delusion nor agrees with it, and works on what the patient does accept: distress, anxiety, poor sleep, and the trouble the belief causes at home and work. - 2
Assess risk
Jealous, erotomanic, persecutory and querulant patients are asked whether they have threatened, followed or harmed anyone. Where a named person is at serious risk, the duty to protect them can override confidentiality, and admission, if necessary compulsory, is considered. - 3
Treat
Trials are lacking, but in case series an antipsychotic at a modest dose helps about half of patients; no drug is preferred, pimozide included, and somatic delusions respond best. An SSRI can help somatic types and accompanying depression. Cognitive therapy aims for doubt rather than surrender of the belief. - 4
Follow up
Depression, sometimes severe, can emerge as the delusion fades, and is treated. Hearing aids, company and reduced isolation help older patients.
Acute and transient psychotic disorders
Treatment is that of a first episode of psychosis: a calm setting, at home if safe or briefly in hospital, a low-dose antipsychotic, and a benzodiazepine for agitation and sleep, with help for the stressor. Because recurrence is common, the antipsychotic is usually continued after recovery, often for a year or more as after any first episode, and then tapered slowly under review; follow-up watches for recurrence and for evolution into schizophrenia or a mood disorder.
Schizoaffective disorder
An antipsychotic is the basis, as in schizophrenia, with the mood episode treated as well:
- Manic or mixed type: an antipsychotic with lithium or, where its pregnancy restrictions allow, valproate, for acute treatment and prevention.
- Depressive type: an antipsychotic with an antidepressant.
- Persistent symptoms despite two antipsychotics: clozapine; ECT in severe mania, depression or catatonia.
- Psychological and social care as for schizophrenia: CBT, family intervention, psychoeducation, help with work and housing, and physical health monitoring.
Induced delusional disorder
The partners are separated where possible, for example by admitting the primary partner, who is treated for the underlying disorder. The secondary partner is supported and treated only if the belief persists.
Epidemiology
| Disorder | Frequency | Who |
|---|---|---|
| Schizotypal | estimates range from under 1 to about 4 per cent of the population | onset in adolescence; slightly commoner in men |
| Persistent delusional | point prevalence about 0.03 per cent, lifetime risk about 0.2 per cent; 1 to 2 per cent of psychiatric admissions | onset usually in middle or late adult life; sexes about equal, jealousy commoner in men, erotomania in women |
| Acute and transient | uncommon; about ten times as frequent in low-income settings in a WHO study | about twice as common in women; onset later in high-income countries |
| Schizoaffective | lifetime prevalence about 0.3 to 0.8 per cent | commoner in women, mainly the depressive type; the manic type starts younger |
| Induced delusional | rare | two isolated, closely bound people; most are couples, siblings or a parent and child |
Delusional disorder is probably underestimated, because patients avoid psychiatric services and keep their working lives.
Prognosis
Over about four and a half years after a first episode, the diagnosis stayed the same in about nine in ten patients diagnosed with schizophrenia, but in only about seven in ten with schizoaffective disorder, six in ten with delusional disorder and a little over half with an acute and transient psychotic disorder; most of those whose diagnosis changed were later diagnosed with schizophrenia.
| Disorder | Usual course | What worsens it |
|---|---|---|
| Schizotypal | stable, lifelong; a minority develops schizophrenia | negative symptoms, substance use |
| Persistent delusional | chronic in many; with treatment a third to a half remit and others improve | insidious onset, long duration, isolation, sensory loss |
| Acute and transient | recovery within weeks to months; recurrence common | slow onset, flat affect, schizophrenic symptoms |
| Schizoaffective | between schizophrenia and mood disorder; often a full recovery from manic episodes, with more residual symptoms after depressive ones | depressive type, persisting psychosis between episodes |
| Induced delusional | the secondary partner often recovers on separation; the primary partner follows the course of the underlying disorder | continued isolation together |
Suicide is a risk throughout, especially in schizoaffective disorder and in depression that follows a delusion, and is assessed at every review (see suicidal and aggressive behaviour). Patients with any of these diagnoses are followed for recurrence, for evolution into schizophrenia or a mood disorder, and, in delusional disorder, for risk to others.
Check yourselfAnswer, then say how sure you were: a lucky guess still counts as a weak point.
1A 58-year-old man has been certain for eight months that his wife is having an affair. He checks her phone and underwear, follows her to work and has found "proof" in a car parked outside. He hears no voices, his mood is normal and he still runs his business. What matters most at this first assessment?
2Two days after her brother's sudden death, a 28-year-old woman becomes perplexed and frightened, with voices, visions and delusions whose content changes from hour to hour, and her mood swings between elation and terror. She has no history of mental illness and takes no drugs. She is fully well three weeks later. What is the ICD-10 diagnosis?
3A 31-year-old man is admitted with elation, overactivity, no need for sleep and pressured speech. Throughout the same three-month episode he has heard voices commenting on his actions and believes his thoughts are broadcast to the world. Both groups of symptoms are equally prominent. What is the most likely ICD-10 diagnosis?
4A 24-year-old has been odd and isolated since adolescence, believes in telepathy, senses a "presence" in rooms, speaks in a vague, overelaborate way and is suspicious of colleagues, but has never had sustained hallucinations or delusions. Where does ICD-11 classify the most likely diagnosis?
5Two elderly sisters who have lived together in isolation for decades both insist that neighbours are pumping gas into their house. The older, dominant sister developed the belief first and has a persistent delusional disorder; the younger has no other psychiatric history. What is the most useful first step for the younger sister?