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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Acute psychosis is a PRESENTATION, not a diagnosis — always seek the underlying cause
- Differential: schizophrenia, bipolar mania, substance-induced, organic (delirium, encephalitis, brain tumour), drug-related
- Urgent assessment: full psychiatric history, MSE, physical examination, bloods, urine drug screen, CT head if indicated
- Exclude organic causes FIRST: delirium, encephalitis, space-occupying lesion, metabolic derangement
- Acute management: oral antipsychotic (olanzapine, risperidone, haloperidol) + IM lorazepam if agitated
- Rapid tranquillisation protocol if severely agitated/violent: IM lorazepam or IM haloperidol + promethazine (NICE CG178)
Overview
Acute psychosis refers to the acute onset of psychotic symptoms — loss of contact with reality manifesting as delusions, hallucinations, disorganised speech and behaviour, and impaired insight. It is a clinical presentation rather than a specific diagnosis and requires systematic evaluation to identify the underlying cause. Causes include primary psychotic disorders (schizophrenia, schizoaffective disorder), mood disorders (bipolar mania, psychotic depression), substance-induced psychosis (cannabis, cocaine, amphetamines, novel psychoactive substances), organic causes (delirium, encephalitis, brain tumour, metabolic disturbance), and medication-induced psychosis (steroids, levodopa). First-episode psychosis (FEP) is a critical presentation requiring urgent assessment and referral to early intervention in psychosis (EIP) services.
Epidemiology
First-episode psychosis has an annual incidence of approximately 30 per 100,000 population in the UK. Peak onset is 18–25 years in males and 25–35 years in females. In the UK, the incidence is higher in urban areas and in certain ethnic minority groups, likely reflecting socioeconomic deprivation and migration-related stress. Cannabis use (particularly high-potency "skunk") is a significant contributing factor in the UK context. The duration of untreated psychosis (DUP) is a strong predictor of outcomes — shorter DUP correlates with better prognosis, which underpins the urgency of early intervention services.
Clinical Features
Symptoms
Delusions: fixed, false beliefs — persecutory, grandiose, referential, bizarre
Hallucinations: auditory most common (voices); also visual, tactile, olfactory
Disorganised thinking and speech: tangential, loose associations, incoherent
Disorganised or bizarre behaviour: agitation, aggression, catatonia
Impaired insight: patient may not recognise they are unwell
Acute confusion, disorientation, fluctuating consciousness (suggests ORGANIC cause)
Visual hallucinations (more suggestive of organic cause, substance-induced, or delirium)
Risk behaviours: responding to command hallucinations, aggression, self-harm, wandering
Signs
Bizarre or disorganised behaviour, poor self-care
Responding to unseen stimuli, talking to self
Suspiciousness, paranoia, guarded manner
Agitation, restlessness, or catatonic immobility
Signs of organic cause: fever, focal neurology, clouded consciousness, visual hallucinations
Investigations
First-line
Full physical examinationIncluding neurological examination — exclude delirium, encephalitis, head injury, substance intoxication/withdrawal
BloodsFBC, CRP, U&Es, LFTs, TFTs, glucose, calcium, B12/folate — exclude metabolic and endocrine causes
Urine drug screenEssential in first-episode psychosis — cannabis, amphetamines, cocaine, novel psychoactive substances
MSE and risk assessmentDetailed mental state examination, risk to self and others, capacity assessment
Second-line
CT/MRI headIf first-episode psychosis, atypical features, or suspicion of organic cause
HIV, syphilis serologyConsider in first-episode psychosis — neurosyphilis and HIV encephalopathy can present with psychosis
Anti-NMDA receptor antibodiesIf young woman with acute psychosis + seizures/movement disorder/autonomic instability → autoimmune encephalitis
Specialist
EEGIf temporal lobe epilepsy or encephalitis suspected
Lumbar punctureIf encephalitis suspected (fever, seizures, confusion, focal neurology)
1
Immediate safety and assessment
- Ensure safety of patient and staff — calm, low-stimulus environment
- De-escalation techniques first-line for agitation
- Assess capacity and consider Mental Health Act if patient refuses assessment/treatment and is at risk
2
Rapid tranquillisation (if severely agitated/violent)
- Oral lorazepam preferred if patient will accept oral medication
- IM lorazepam 1–2 mg if oral refused
- IM haloperidol 5 mg + promethazine 25–50 mg if lorazepam insufficient
- Monitor pulse, BP, respiratory rate, temperature, SpO₂ every 15 minutes after rapid tranquillisation
- If on IM haloperidol → ECG monitoring (QTc prolongation risk)
3
Antipsychotic initiation
- Start oral atypical antipsychotic: olanzapine, risperidone, aripiprazole, or quetiapine
- Low dose initially, titrate over days to weeks
- Review at 2–4 weeks — if no response at adequate dose, consider alternative antipsychotic
4
Referral and follow-up
- Refer to Early Intervention in Psychosis (EIP) service if first-episode psychosis (NICE mandated)
- Treat underlying cause if identified (substance, organic, mood disorder)
- If substance-induced: monitor for 1 month off substance — if psychosis persists, may indicate primary psychotic disorder
- CBTp and family intervention as per NICE CG178
Complications
- Self-harm and suicide: Elevated risk in acute psychosis — command hallucinations, paranoia, distress
- Violence and aggression: Rare but possible — associated with persecutory delusions and command hallucinations
- Self-neglect: Not eating, drinking, or maintaining personal hygiene
- Missed organic diagnosis: Failure to exclude delirium, encephalitis, or brain tumour can be fatal
- Prolonged DUP: Delayed treatment worsens long-term outcomes in primary psychotic disorders
UKMLA Exam Tips
- 1Acute psychosis is a PRESENTATION — always determine the CAUSE (primary psychotic, mood, substance, organic)
- 2Visual hallucinations + confusion + fluctuating consciousness → think ORGANIC (delirium, encephalitis, drugs) NOT schizophrenia
- 3Young woman + acute psychosis + seizures + dyskinesia → anti-NMDA receptor encephalitis (exam favourite)
- 4Cannabis-induced psychosis: symptoms usually resolve within 1 month of cessation; if persistent → primary psychosis
- 5Rapid tranquillisation: IM lorazepam first; IM haloperidol + promethazine if needed. Monitor observations every 15 minutes
- 6First-episode psychosis → ALWAYS refer to Early Intervention in Psychosis (EIP) service
- 7Neuroleptic malignant syndrome: fever + rigidity + autonomic instability + raised CK after antipsychotic — medical emergency
practicetest your knowledge on acute psychosisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — psychiatry and beyond.
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