Piazza, Giulia G; Iskandar, Georges; Hennessy, Vanessa; Zhao, Hannah; Walsh, Katie; McDonnell, Jeffrey; Terhune, Devin Blair; Das, Ravi K and Kambo, Sunjeev K. 2022. Pharmacological modelling of dissociation and psychosis: An evaluation of the Clinician Administered Dissociative States Scale and Psychotomimetic States Inventory during nitrous oxide (‘laughing gas’)-induced anomalous states. Psychopharmacology, 239(7), pp. 2317-2329. ISSN 0033-3158 [Article]

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Abstract or Description

Rationale: A significant obstacle to an improved understanding of pathological dissociative and psychosis-like states is the lack of readily implemented pharmacological models of these experiences. Ketamine has dissociative and psychotomimetic effects, but can be difficult to use outside of medical and clinical-research facilities. Alternatively, nitrous oxide (N 2 O) - like ketamine, a dissociative anaesthetic and NMDAR antagonist – has numerous properties that make it an attractive alternative for modelling dissociation and psychosis. However, development and testing of such pharmacological models relies on well-characterized measurement instruments.

Objectives: To examine the factor structures of the Clinician Administered Dissociative States Scale (CADSS) and Psychotomimetic States Inventory (PSI) administered during N 2 O inhalation in healthy volunteers.

Methods: Secondary analyses of data pooled from three previous N 2 O studies with healthy volunteers.

Results: Effect sizes for N 2 O-induced dissociation and psychotomimesis were comparable to effects reported in experimental studies with sub-anesthetic ketamine in healthy volunteers. Although, like ketamine, a three-factor representation of N 2 O-induced dissociation was confirmed, a more parsimonious two-factor model might be more appropriate. Bayesian exploratory factor analysis suggested that N 2 O-induced psychosis-like symptoms were adequately represented by two negative and two positive symptom factors. Hierarchical cluster analysis indicated minimal item overlap between the CADSS and PSI.

Conclusion: N 2 O and ketamine produce psychometrically similar dissociative states, although parallels in their psychosis-like effects remain to be determined. The CADSS and PSI tap largely non-overlapping experiences under N 2 O and we propose the use of both measures (or similar instruments) to comprehensively assess anomalous subjective states produced by dissociative NMDAR antagonists.

Item Type:	Article
Identification Number (DOI):	https://doi.org/10.1007/s00213-022-06121-9
Additional Information:	The online version of the article contains supplementary material available at https://doi.org/10.1007/s00213-022-06121-9 This study was funded by a grant from the Sir Bobby Charlton Foundation award to SKK, VH and RKD. GP is a recipient of a Wellcome Trust PhD studentship. The authors declare that they have no conflict of interest.
Keywords:	Dissociation, psychosis, psychotomimesis, CADSS, dissociative anaesthetic, nitrous oxide, ketamine, NMDA, glutamate
Departments, Centres and Research Units:	Psychology
Dates:	Date Event 15 March 2022 Accepted 26 March 2022 Published Online July 2022 Published
Item ID:	31678
Date Deposited:	04 Apr 2022 09:35
Last Modified:	20 Jun 2022 13:45
Peer Reviewed:	Yes, this version has been peer-reviewed.
URI:	https://research.gold.ac.uk/id/eprint/31678

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