Red flag symptoms - Hallucinations

Establishing risk is top priority in the initial consultation, by Dr Pipin Singh.

A history of alcohol abuse may suggest alcoholic encephalopathy as a cause (Photograph: SPL)
A history of alcohol abuse may suggest alcoholic encephalopathy as a cause (Photograph: SPL)

This is a rare complaint; however it needs to be taken very seriously. Given the nature of the symptom, the patient may come to your attention from a relative or partner.

Establishing risk must be top priority in the initial consultation, however gathering relevant information may take a number of consultations.

Exploring this symptom can be difficult but asking open questions could yield a significant amount of information.

A hallucination is defined as a perception in the absence of an external stimulus. Patients often lack insight in contrast to pseudo-hallucinations.

Hallucinations can be visual, auditory, tactile (the feeling of something crawling on one's skin), gustatory (an unusual sense of taste) or olfactory (unusual sense of smell).

Patient may complain of hypnagogic hallucinations which are experienced when falling asleep or hypnapompic hallucinations which present on waking up.

Possible causes


  • Space occupying lesion.
  • Temporal lobe epilepsy.
  • Migraine.


  • Encephalopathy.


  • Prescription medications.
  • OTC medications.
  • Recreational drugs and alcohol.


  • Schizophrenia.
  • Depression.
  • Dementia.
  • Schizoaffective disorder.

Organic causes must always be considered and include neurological causes, such as space occupying lesion, temporal lobe epilepsy, migraine; metabolic causes, such as an encephalopathic process, and iatrogenic causes, such as prescription medications.

It is important to enquire about use of OTC medications and recreational drugs, such as amphetamines. Alcohol abuse can lead to encephalopathy or delirium tremens. An acute delirium may lead to visual hallucinations.

Psychiatric diagnoses to consider include schizophrenia, schizoaffective disorder, depression and dementia.

History and diagnosis
History is crucial to the diagnosis. Specific questions should focus on neurological symptoms, a comprehensive drug history, a recreational drug history, alcohol history and a mood history.

If the hallucinations are auditory then explore whether the hallucinations are commanding the patient to harm themselves or others. If schizophrenia is suspected, then Schneider's first rank symptoms need to be explored.

Ask about family history of any psychiatric problems or neurological problems.

It is vital to assess risk thoroughly. Consider whether the patient is a risk to themselves or others. If so, appropriate steps must be taken and this may involve hospital admission, urgent crisis assessment and involvement from community mental health or early intervention psychosis team.

Examination will vary depending on the type of hallucination that presents, but core components include temperature, BP, pulse and respiratory rate.

A neurological examination may reveal a focal deficit and should also include the cranial nerves. A mental state examination is necessary for formulating psychiatric diagnosis and cognitive testing, such as the mini-mental state examination, may be necessary.

Investigations in primary care include FBC, U&Es, CRP, LFT and chest X-ray.

More detailed investigations, such as a CT brain, MRI brain and EEG will require referral to secondary care.

  • Dr Singh is a GP in Wallsend, North Tyneside

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