A Review of Multimodal Hallucinations: Categorization, Assessment, Theoretical Perspectives, and Clinical Recommendations

Abstract

Hallucinations can occur in different sensory modalities, both simultaneously and serially in time. They have typically been studied in clinical populations as phenomena occurring in a single sensory modality. Hallucinatory experiences occurring in multiple sensory systems—multimodal hallucinations (MMHs)—are more prevalent than previously thought and may have greater adverse impact than unimodal ones, but they remain relatively underresearched. Here, we review and discuss: (1) the definition and categorization of both serial and simultaneous MMHs, (2) available assessment tools and how they can be improved, and (3) the explanatory power that current hallucination theories have for MMHs. Overall, we suggest that current models need to be updated or developed to account for MMHs and to inform research into the underlying processes of such hallucinatory phenomena. We make recommendations for future research and for clinical practice, including the need for service user involvement and for better assessment tools that can reliably measure MMHs and distinguish them from other related phenomena.

Hallucinations Under Psychedelics and in the Schizophrenia Spectrum: An Interdisciplinary and Multiscale Comparison

“… 62 , 64 , 65 AH occur alone approximately half of the time, 66 , 67 while hallucinations in other modalities almost never occur alone. 66 , 68 Some studies report that multimodal or “fused” hallucinations (MMH; eg, seeing a talking head) 69 are highly prevalent in SCZs, 65 , 70–72 whereas other reports suggest that these hallucinations are rare. 73 By contrast, hallucinations induced by 5-HT 2A agonists occur primarily in the visual domain 74 (a shared feature with neurological disorders, such as Parkinson’s disease and Lewy body dementia).…”

The feeling, embodiment and emotion of hallucinations in first episode psychosis: A prospective phenomenological visual-ecological study using novel multimodal unusual sensory experience (MUSE) maps

“…The relevance of MMH to clinical work has been empirically indicated for almost 50 years [ 6 , 14 ], with renewed interest in recent years with considerations of MMH's relevance, categorisation, clinical management and potential interrelationship with trauma [ [15] , [16] , [17] , [18] ]. MMH involve two or more modalities and can either be simultaneous (multimodal at once) or serial (different modalities at different times) [19] .…”

Cognition, hallucination severity and hallucination-specific insight in neurodegenerative disorders and eye disease

“…An important limitation of the current study was that it was restricted to the use of the MMSE total score (which is not the best measure of executive functioning) as the only cognitive variable available across all groups of patients. In the future, it would be useful to either have a test with sufficient sensitivity to be able to also detect mild cognitive impairments (Bak, 2006) or to have a complete cognitive battery to reliably detect small changes in performance across different underlying cognitive domains that are known to be linked to VHs in patients with neurodegenerative disorders (e.g., executive function, working memory and visuo-spatial tasks- Montagnese and Leptourgos, 2021). Furthermore, future research should examine what kinds of specific cognitive deficits are predictive of poor insight.…”