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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Organic and substance-induced psychosis

Psychiatry · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Psychosis with acute brain or toxic dysfunction

Fluctuating consciousness, fever, seizure, focal neurology, severe agitation, autonomic instability, hypoxia, hypoglycaemia, head injury or a dangerous exposure requires emergency medical treatment before assuming a primary psychiatric disorder.

Action: Use ABCDE, bedside glucose, observations and focused neurological examination, stop further exposure when safe and obtain toxicology or emergency specialist advice. Treat the physiological syndrome, provide a low-stimulation safe setting and arrange parallel psychiatric assessment for suicide, violence, capacity and safeguarding.

Overview

Recognise psychosis caused or shaped by physical illness, prescribed medicines, intoxication or withdrawal, identify neurological and delirious emergencies, and integrate cause-specific medical treatment with immediate psychiatric safety and follow-up.

Start with physiology and chronology. Determine whether attention, consciousness or orientation fluctuates, whether observations are abnormal and whether seizure, injury or focal neurology is present. Obtain a complete exposure history covering prescribed drugs, over-the-counter products, supplements, recreational substances, alcohol, nicotine and recent cessation. Ask what was taken, how much, by which route, when, with what else and whether sleep was lost. Seek packaging, prescription records and collateral when safe and lawful; the person may not know adulterants or exact potency.

Different mechanisms produce different patterns. Stimulants can cause hyperarousal, insomnia, stereotypy and persecutory psychosis. High-potency cannabis can precipitate paranoia and hallucinations, especially in vulnerable people. Hallucinogens alter perception and meaning; dissociatives can impair behaviour and awareness. Alcohol or sedative withdrawal can produce autonomic activation, tremor, seizure and delirium. Corticosteroids and dopaminergic drugs may cause mood and psychotic change. Anticholinergic toxicity causes agitation with peripheral signs, while serotonergic and dopamine-blocking syndromes have distinctive neuromuscular clues.

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Toxicology interpretation

A patient with paranoia has a urine test positive for cannabis metabolites four days after last reported use. Which interpretation is most accurate?

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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE CG120 psychosis with substance misuseIntegrated assessment, substance history and treatment across mental-health and substance services.
  • NICE CG103 delirium recommendationsRecognition, assessment and management of acute fluctuating brain dysfunction.
  • NICE CG178 psychosis and schizophrenia recommendationsDifferential assessment, physical investigation and coordinated psychosis care.
  • NICE NG10 violence and aggression recommendationsDe-escalation, observation and proportionate management of acute behavioural danger.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Medical and neurological causes include delirium from infection, hypoxia or metabolic disturbance; epilepsy; autoimmune or infectious encephalitis; endocrine disorders; neurodegeneration; brain lesions and porphyria in selected phenotypes. Anti-NMDA-receptor encephalitis can begin with psychiatric change before seizure, dyskinesia, catatonia or autonomic instability. No universal blood panel excludes these conditions. Investigation follows age, tempo, examination and systemic clues, and should escalate when the course is atypical or fails to improve as expected.

Causation is rarely proved by one test. Urine drug screening has finite detection windows, may miss novel substances and can remain positive after intoxication has ended. Prescribed medicines can explain a positive result. Temporal proximity strengthens a substance formulation, while psychosis predating use, recurring during abstinence or persisting well beyond the expected toxic state raises an independent disorder. Both can coexist: substance exposure may precipitate relapse in someone with established vulnerability. State evidence and uncertainty rather than making a moral judgement.

Management combines supportive medical care, cause-specific treatment and psychiatric safety. Reduce stimulation, correct oxygenation, glucose, fluids, electrolytes and temperature as indicated, and use poison or withdrawal protocols with appropriate monitoring. Avoid reflexive antipsychotic escalation in delirium, catatonia or toxic syndromes without senior review. Once stable, offer non-judgemental substance support, harm-reduction advice and follow-up that reassesses cognition, mood and psychosis during recovery. Communicate driving, safeguarding and medicine decisions explicitly.

Key points

  • Organic psychosis is a clinical formulation linking psychotic symptoms to brain dysfunction or systemic disease; identify the syndrome and mechanism rather than using the label as an endpoint.
  • Substance-induced psychosis requires a precise timeline of dose, route, frequency, potency, last use, sleep, co-exposures, withdrawal and symptom persistence.
  • Delirium is suggested by acute onset, impaired attention and fluctuating arousal and remains a medical emergency even when behaviour looks primarily psychiatric.
  • Cannabis, stimulants, hallucinogens, steroids, dopaminergic medicines, anticholinergic toxicity and alcohol or sedative withdrawal are important but not exhaustive causes.
  • A positive toxicology result shows detected exposure, not causation, dose, impairment or the absence of an independent psychotic disorder.
  • Use phenotype-led blood tests, ECG, toxicology, imaging, EEG and cerebrospinal-fluid investigation; normal routine tests cannot exclude encephalitis or epilepsy.
  • Treat intoxication, withdrawal, infection, metabolic disturbance or neurological disease while also addressing commands, suicide, violence, vulnerability and dependants.
  • Follow the course after medical recovery and supported abstinence because persistent or recurrent symptoms may reveal a primary psychotic or affective disorder.

Aetiology

01

Intoxication

Cannabis, stimulants, hallucinogens, dissociatives and mixed exposures can disturb perception, salience, arousal and judgement during or after use.

02

Withdrawal

Abrupt reduction in alcohol, benzodiazepines or other sedatives can cause autonomic activation, seizure, hallucinations and delirious psychosis.

03

Prescribed medicine effects

Corticosteroids, dopaminergic agents, anticholinergic toxicity and other treatments may provoke psychotic, affective or confused states in susceptible people.

04

Neurological and systemic disease

Encephalitis, epilepsy, endocrine disturbance, infection, hypoxia, metabolic illness and structural brain disease can disrupt reality testing through distinct mechanisms.

Pathophysiology

  1. 1
    Arousal and salience excess

    Stimulant and stress pathways can heighten vigilance and assign excessive threat or meaning to ambiguous perceptions and ordinary events.

  2. 2
    Global cerebral dysfunction

    Hypoxia, inflammation, metabolic disturbance and toxins impair attention and network integration, producing the fluctuating cognition characteristic of delirium.

  3. 3
    Withdrawal hyperexcitability

    Loss of chronic inhibitory drug effects leaves unopposed neuronal excitation, causing autonomic activation, tremor, seizure and perceptual disturbance.

  4. 4
    Immune and seizure mechanisms

    Autoantibody-mediated receptor dysfunction or epileptic network activity can initially alter behaviour and perception before more recognisable neurological signs emerge.

Clinical features and red flags

Delirious psychosis

Acute hallucinations or paranoid behaviour occur with impaired attention, disorientation or fluctuating arousal, pointing to global brain dysfunction rather than isolated psychosis.

Stimulant pattern

Prolonged wakefulness, sympathetic activation, repetitive behaviour, formication and persecutory ideas after stimulant exposure support intoxication while cardiovascular danger is assessed.

Withdrawal pattern

Tremor, sweating, tachycardia, agitation, seizure or visual hallucinations after alcohol or sedative reduction raises a monitored withdrawal emergency.

Encephalitic pattern

Rapid psychiatric change followed by seizure, catatonia, memory impairment, dyskinesia or autonomic instability requires urgent neurological investigation.

Persistent dual diagnosis

Symptoms continuing or recurring outside expected intoxication and withdrawal windows suggests an independent psychotic disorder that substance use may worsen.

Red flags requiring action

  • Impaired attention with fluctuating arousal identifies possible delirium, even when hallucinations, paranoia or agitation dominate the visible presentation.
  • New seizure, dyskinesia, catatonia, focal deficit, severe headache, neck stiffness or autonomic fluctuation raises encephalitis, epilepsy or structural disease.
  • Hyperthermia, rigidity, clonus, cardiovascular instability or marked creatine-kinase elevation after medicine or drug exposure may indicate a life-threatening toxic syndrome.

Investigations

  1. 01
    ABCDE and delirium assessmentFirst step
    Why
    Identify physiological instability, glucose disturbance, injury, impaired attention and fluctuating consciousness.
    Interpretation and limitations
    Abnormal physiology or delirium signs demand immediate medical treatment; apparent cooperation during one moment does not exclude a fluctuating syndrome.
  2. 02
    Exposure and withdrawal timeline
    Why
    Link prescribed, non-prescribed and recreational substances with sleep, symptoms and cessation.
    Interpretation and limitations
    Chronology supports or weakens causation but should include unknown potency and co-exposure; persistence during verified recovery requires diagnostic review.
  3. 03
    Targeted toxicology and laboratory tests
    Why
    Detect relevant exposure, organ injury, infection, metabolic disturbance and treatment constraints.
    Interpretation and limitations
    Interpret analytes within detection windows and clinical phenotype. A negative screen misses many substances, while a positive result does not prove current impairment.
  4. 04
    Neurological investigations
    Why
    Assess seizure, encephalitis, structural disease or inflammatory brain dysfunction when indicated.
    Interpretation and limitations
    MRI, EEG and cerebrospinal fluid answer different questions; normal early findings may not end investigation when catatonia, dyskinesia or autonomic change progresses.

Differential diagnosis

01

Primary psychotic disorder

Psychosis may predate substance use, recur independently or persist beyond expected recovery, while exposure still worsens severity and engagement.

02

Affective episode

Mania or severe depression can include psychosis and may itself be precipitated by substances, medicines, sleep loss or childbirth.

03

Trauma and dissociation

Intrusions, hypervigilance, depersonalisation and dissociative voices require trauma-sensitive assessment and can coexist with substance use or psychosis.

04

Neurocognitive disorder

Dementia-related hallucinations or misidentification arise within progressive cognitive decline rather than an isolated transient toxic state.

Management

01Unstable presentationTreat brain and body emergenciesFirst stepPsychosis coexists with altered arousal, seizure, fever, injury or physiological instability.+
  1. 1Use ABCDE, glucose, observations and focused neurological examination, summon emergency support and reduce environmental hazards.
  2. 2Obtain an exposure timeline, ECG and phenotype-led laboratory, toxicology, imaging, EEG or cerebrospinal-fluid investigation without delaying stabilisation.
  3. 3Treat the identified medical or toxic syndrome and provide parallel psychiatric observation, capacity assessment and safeguarding review.
02Substance-linked psychosisSupport recovery and preserve uncertaintySymptoms arise close to intoxication, withdrawal or repeated psychoactive exposure.+
  1. 1Clarify substance, route, quantity, potency, last use, sleep loss, co-exposures, previous episodes and the person's own causal understanding.

Complications

01

Physiological collapse

Hyperthermia, arrhythmia, seizure, aspiration, dehydration, rhabdomyolysis and organ injury can accompany severe intoxication, withdrawal or toxic agitation.

02

Accidental and interpersonal harm

Fear, impaired judgement, altered perception and disinhibition can lead to falls, traffic injury, confrontation, exposure or unintended violence.

03

Persistent psychotic illness

Symptoms may continue after the acute exposure or recur, revealing sustained vulnerability and need for longitudinal specialist treatment.

04

Fragmented service care

Exclusion between substance, medical and mental-health services can leave both the precipitating exposure and psychosis insufficiently treated.

Monitoring and follow-up

  • Repeat consciousness, attention, observations, hydration, temperature, movement and neurological findings because toxic and encephalitic syndromes can evolve rapidly.
  • Track last exposure, sleep, withdrawal features and psychotic symptoms against expected pharmacological time course and collateral evidence.
  • Review ECG, electrolytes, renal and hepatic function, creatine kinase and other organ markers when the suspected agent or clinical syndrome warrants them.
  • Reassess suicide, violence, accidental harm, exploitation, self-neglect and capacity as intoxication resolves and the person's account becomes clearer.
  • Arrange follow-up during supported abstinence or medical recovery and document whether persistent symptoms require early-intervention or specialist neurological review.

Special situations

Detection is not causation

A toxicology result must be reconciled with timing, phenotype and expected duration rather than used as the diagnosis by itself.

Visual phenomena are contextual

Visual hallucinations can occur in delirium, withdrawal, neurological illness and primary psychosis, so modality alone cannot determine cause.

Sleep loss is active

Prolonged wakefulness can amplify suspiciousness, perceptual change and disorganisation and may mediate part of a stimulant-associated presentation.

Dual processes are common

Substance use and primary psychosis may reinforce each other, making integrated care more useful than forcing exclusive service ownership.

Course can revise diagnosis

A provisional toxic formulation should be revisited when symptoms outlast exposure or recur during periods of credible abstinence.

Common pitfalls

  1. 01

    Calling acute fluctuating hallucinations schizophrenia without testing attention and physiological stability.

  2. 02

    Treating a positive urine screen as proof that the detected drug caused current psychosis.

  3. 03

    Assuming a negative routine toxicology screen excludes novel or rapidly cleared substances.

  4. 04

    Missing steroid, dopaminergic, anticholinergic or withdrawal causes because recreational drugs dominate the history.

  5. 05

    Using substance use to deny access to early-intervention or continuing mental-health care.

  6. 06

    Failing to reconsider encephalitis when psychiatric symptoms evolve into seizure, catatonia or dyskinesia.

  • Agitated persecutory behaviour during stimulant intoxication, alcohol withdrawal or hallucinogen use can cause rapid accidental, suicidal or interpersonal harm.
  • Abrupt psychosis in later life, during pregnancy or after childbirth, or with endocrine or systemic symptoms warrants a widened physical differential.
    • 05
    Longitudinal psychiatric review
    Why
    Reassess psychosis, mood, cognition and function after physiological recovery and reduced exposure.
    Interpretation and limitations
    Resolution supports a causal toxic or medical formulation, while recurrence or persistence prompts evaluation for primary psychotic, affective and neurocognitive disorders.
    2
    Use supportive or protocol-specific treatment, address immediate risk and engage addiction expertise without punitive or confrontational communication.
  • 3Reassess after the expected recovery period, arrange early follow-up and record which persistence or recurrence should trigger primary-psychosis evaluation.
    • 03Atypical progressionEscalate neurological investigationEscalationSymptoms persist unexpectedly or develop seizure, catatonia, dyskinesia, cognitive decline or autonomic change.+
    1. 1Repeat neurological and cognitive examination and review medicines, toxins, infection, autoimmune symptoms and collateral chronology.
    2. 2Involve neurology and acute medicine and select MRI, EEG, lumbar puncture and immune or infectious tests for the evolving phenotype.
    3. 3Maintain nutrition, hydration, thrombosis prevention and behavioural safety while avoiding medicines that may worsen the unresolved syndrome.