Hallucinations as a presenting complaint in emergency departments: Prevalence, diagnosis, and costs.

Hallucinations occur in the context of many disorders. When experienced as distressing, they are a likely cause of presentation to emergency departments. Knowledge about the rates, diagnoses, and associated costs of hallucinations in emergency departments however is currently lacking. In this study, we analysed patients' presenting complaints in Western Australia's Emergency Department Data Collection dataset during a two year period (n = 1,798,754). Visits to emergency departments because of distressing hallucinations were more common than previously assumed. Hallucinations (auditory, visual, undifferentiated modality) accounted for 1.8% of all mental health-related presentations and 0.09% of all general health presentations (84.7 per 100,000 persons). Psychotic disorders accounted for a third of all presentations, and hallucinations without a clear medical or psychiatric cause represented 17% of the sample. Hallucination presentations had significantly prolonged lengths of stay compared to other mental health presentations (15 vs 7.5h, p < 0.001) and were linked to frequent re-admissions (average of 7.4 visits per year). Cost estimates revealed that hallucinations were in the top-10 most costly mental health complaint, and twice as costly to treat as delusions. Altogether, the service utilisation and care needs of people with distressing hallucinations outside of mental health services appear much larger than usually estimated.