Seeing ghosts? Hearing voices? Feeling a dread or anxiety that is extreme and unexpected? Do you smell things others do not? Perhaps you are hallucinating… Hallucinations are sensations (seen, heard, felt, or smelled) that are not real i.e. they are not based on reality. For clarity, proper hallucinations, in this article anyway,  refer to the repeated experiencing of things that are not real, as opposed once-off instances.

Common causes include:

  • High fever (especially in children) – this is quite common and can be very scary for kids.
  • Psychotic illness (a psychiatric condition) – the defining characteristic of psychotic illnesses is that the patient is not completely in touch with reality, some or even all of the time.
  • Insufficient sleep – this is also quite common, but only really when sleep deprivation becomes significant such as is seen in students studying for exams, the military, sailors, certain jobs, etc.
  • Medication side effects
  • Alcohol and drug intoxication
  • Alcohol and drug withdrawal
  • Dehydration
  • Diabetic coma
  • Brain conditions such as brain abscess, brain tumour, and meningitis (infection of the membranes surrounding the brain)
  • Alzheimer’s disease – the early and middle phases of this dreadful condition can involve hallucinations, which can be very frightening for the patient and the family.

As you can see there is a long list of possible causes but several can be easily excluded or diagnosed quite quickly. The doctor will usually assess mental state (considering mental illness) and perform a careful physical examination. Referral to a specialist (psychiatrist or neurologist) may be needed. Tests that may be needed include:

  • CT or MRI scan of the brain – computer assisted techniques that create detailed images.
  • Blood tests to check for alcohol or drug usage.

Hallucinations are sometimes simply explained but there are also serious medical and psychiatric conditions that can cause hallucinations.