Psychotic Disorders: Classification, Assessment and Other Presentations

Introduction

Psychosis describes a mental state in which contact with reality is impaired, typically manifesting as delusions, hallucinations, or significant disorganisation of thought and behaviour. It is a symptom complex, not a diagnosis in itself - psychosis is the final common pathway of a wide range of underlying causes, from schizophrenia and mood disorders to substance use, autoimmune encephalitis and delirium.¹

Schizophrenia, schizoaffective disorder and delusional disorder are covered as dedicated topics elsewhere. This article covers the general framework for assessing any new psychotic presentation, and the additional presentations that framework needs to capture: brief, self-limiting psychotic episodes; psychosis secondary to an organic or substance cause; and the rare but distinctive shared psychotic disorder.

The single most important principle in psychiatry's approach to a new psychotic presentation is this: never assume a primary psychiatric cause until it has been actively earned by excluding the alternatives, particularly in older adults, first presentations, and anyone with an atypical course.

Classification overview

ICD-11 groups the primary psychotic disorders together, distinguished chiefly by the duration of the episode and the relationship between psychotic and mood symptoms.

This is a spectrum in practice as much as a set of discrete boxes: an initial diagnosis is often provisional, and is revised as the pattern of illness - and its relationship to mood - becomes clearer over subsequent episodes.

A structured approach to a new psychotic presentation

Every new presentation of psychosis should be worked up systematically before a primary psychiatric cause is accepted, regardless of how classical the presentation appears.

1. History - onset and course (sudden versus insidious), a full substance and medication history, past psychiatric and medical history, family history, and a collateral history from someone who knows the patient well
2. Physical examination, including a full neurological examination, looking specifically for focal deficits, tremor, abnormal movements, and signs of systemic illness
3. Mental state examination, systematically covering appearance, speech, mood, thought form and content, perception, cognition and insight
4. Cognitive screening - particularly important in older adults or where organic causes are suspected
5. Investigations - directed at excluding organic and substance causes (see below)
6. Risk assessment - to self, to others, and specifically to any individual named within a delusion
7. Formulation - only once the above is complete does a working diagnosis and management plan follow

Acute and transient psychotic disorder

Characterised by the sudden onset (within about 2 weeks) of psychotic symptoms - delusions, hallucinations, disorganised speech or behaviour - that change rapidly in nature and intensity, and that resolve, usually completely, within one to three months.¹ It is often, though not always, precipitated by an identifiable acute stressor.

• Rapid onset and a fluctuating, kaleidoscopic clinical picture are characteristic - the content and even the type of psychotic symptom can change from day to day
• Emotional turmoil, perplexity and confusion are common accompanying features
• Full recovery to premorbid functioning is the expected outcome, though a minority go on to develop a more persistent psychotic or mood disorder
• Management follows the same general principles as any acute psychosis - a short course of an antipsychotic, a calm and low-stimulation environment, and close follow-up - but treatment is often needed for a shorter period than in schizophrenia given the expectation of full recovery

Organic and substance-induced psychosis

A wide range of medical conditions and substances can produce psychotic symptoms indistinguishable, on mental state examination alone, from a primary psychotic disorder. Certain clinical features should raise suspicion of an organic or substance cause specifically.

Management is directed first at the underlying cause - stopping the causative substance or drug, treating the infection or metabolic derangement - with an antipsychotic used short-term for symptom control where needed. Psychotic symptoms usually resolve once the underlying cause is corrected, though stimulant-induced psychosis can occasionally persist or recur even after abstinence.

Delirium versus primary psychosis

This is the distinction that matters most on a general medical ward, and getting it wrong in either direction is harmful - sedating a delirious septic patient rather than finding the source, or investigating a young man with schizophrenia for encephalitis when the history is clear.

Shared psychotic disorder

Also known as folie à deux, this rare presentation involves a delusion, originating in a dominant individual with a genuine primary psychotic illness, being adopted by one or more people in a close relationship with them - typically a spouse, sibling, or parent-child pair with limited outside social contact.

• The 'secondary' person(s) hold the same delusional belief as the primary, psychotic individual, without necessarily having any other psychotic symptoms of their own
• It typically arises in socially isolated, closely bonded pairs or families, where the secondary individual is often more dependent or suggestible
• Separation of the pair is often, on its own, sufficient to resolve the belief in the secondary individual, which is both diagnostically informative and the mainstay of management
• The primary individual requires full assessment and treatment for their underlying psychotic illness in the usual way

Although rare, it carries practical importance beyond its frequency: where children are the secondary parties, the situation is a safeguarding concern, since a child may be subjected to the consequences of a parent's delusion - withheld medical treatment, withdrawal from school, or restricted nutrition. Assessment should therefore always establish who else in the household shares the belief and whether any dependants are being harmed by it.

Management principles common to all psychotic presentations

• Treat the underlying cause where one is identified - stop the causative substance, correct the metabolic or endocrine abnormality, treat the infection
• Antipsychotic medication for symptomatic control, regardless of underlying cause, where distress or risk warrants it²
• A calm, low-stimulation environment reduces distress and agitation during acute psychosis
• Risk assessment - explicitly ask about command hallucinations, and about any specific individual who features in a delusion
• Early Intervention in Psychosis (EIP) services for any first episode of a primary psychotic disorder - early, intensive, multidisciplinary care in the initial years after onset is associated with better long-term outcomes³
• Family and carer involvement and psychoeducation, balanced against the patient's own wishes and confidentiality

De-escalation and rapid tranquillisation

Acute psychosis is frequently accompanied by agitation, and managing it well is a practical skill worth knowing in outline. De-escalation always comes first: a calm, unhurried approach, adequate personal space, removing an audience, one person speaking, offering food, drink or a quiet room, and addressing the concern the person is actually expressing rather than arguing with the delusion.

• Offer oral medication first where the person will accept it - typically oral lorazepam, or an oral antipsychotic if they are already established on one
• Rapid tranquillisation with intramuscular lorazepam, or IM haloperidol combined with promethazine, is reserved for situations where de-escalation has failed and there is a genuine risk of harm
• Haloperidol requires a recent ECG before use where practicable, because of QTc prolongation, and should be given with an antimuscarinic available for acute dystonia
• Monitor after administration - level of consciousness, respiratory rate, oxygen saturation, pulse, blood pressure and temperature, since the principal risks are over-sedation and respiratory depression
• Have flumazenil available where parenteral benzodiazepines are used, for benzodiazepine-induced respiratory depression
• Rapid tranquillisation is a treatment for behavioural disturbance, not a substitute for finding the cause - the underlying work-up continues regardless

Legal framework

Where a person lacks insight and refuses necessary assessment or treatment for a mental disorder, the Mental Health Act may be needed - most commonly a section 2 for a first presentation where the diagnosis is unclear. Where the psychosis is secondary to a physical illness and the treatment required is physical, the Mental Capacity Act applies instead. Making this distinction correctly is covered in detail in the Mental Health Act article, and it is a routine source of error in exactly this group of patients.

Red flags

Prognosis

Prognosis depends entirely on the underlying cause. Acute and transient psychotic disorder and substance-induced psychosis (once the substance is stopped) generally carry a good prognosis with full recovery expected. Organic psychoses resolve, persist or progress according to the course of the underlying condition. Shared psychotic disorder in the secondary individual typically resolves rapidly with separation, though the primary individual's prognosis follows that of their underlying illness.

Across all causes, prompt recognition, thorough exclusion of reversible organic and substance contributors, and early specialist psychiatric involvement consistently improve outcomes.