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Psychiatry Res. 2017 Jun;252:154-160. doi: 10.1016/j.psychres.2017.01.102. Epub 2017 Feb 24.

Occurrence and co-occurrence of hallucinations by modality in schizophrenia-spectrum disorders.

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Department of Psychiatry, Trinity College Dublin, Ireland.
Department of Psychology, Leeds Trinity University, Leeds, UK.
School of Psychology and Discipline of Biochemistry, National University of Ireland Galway, Ireland.
Department of Psychiatry, University College Cork, Ireland.
Department of Psychiatry, Royal College of Surgeons in Ireland, Dublin, Ireland.
Department of Psychiatry, Queen's University Belfast, Northern Ireland, UK.
Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland.
Schizophrenia Research Institute, NSW, Australia.
School of Psychology, Newcastle University, Newcastle, UK; Northumberland Tyne and Wear NHS Foundation Trust, UK. Electronic address:


It is not only unclear why hallucinations in schizophrenia occur with different prevalence by modality, but also to what extent they do. Reliable prevalence estimates of hallucinations by modality in schizophrenia are currently lacking, particularly for non-auditory hallucinations. Studies have also tended to report lifetime, not point prevalence by modality. This study assessed the prevalence and co-occurrence of hallucinations, for both lifetime and point prevalence, across the auditory, visual, olfactory, and tactile modalities, in people diagnosed with chronic schizophrenia-spectrum disorders in Ireland (N=693) and Australia (N=218). Lifetime prevalence was 64-80% auditory, 23-31% visual, 9-19% tactile, and 6-10% olfactory. Past month prevalence was 23-27% auditory, 5-8% visual, 4-7% tactile, and 2% olfactory. The majority of participants had only hallucinated in one modality, with this nearly always being the auditory. Approximately one-third had hallucinated in two modalities, most commonly the auditory and visual. Most currently hallucinating patients also hallucinated in a single modality, again, nearly always the auditory. Whereas 30-37% of patients with lifetime auditory hallucinations had experienced visual hallucinations, 83-97% of patients with experience of visual hallucinations had experienced auditory hallucinations. These findings help delineate the modality distribution of hallucinations in schizophrenia, and provide an explanatory target for theoretical models.


Auditory; Olfactory; Psychosis; Tactile; Visual

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