Brain Functional Correlates of Resting Hypnosis and Hypnotizability: A Review

This comprehensive review delves into the cognitive neuroscience of hypnosis and variations in hypnotizability by examining research employing functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalography (EEG) methods. Key focus areas include functional brain imaging correlations in hypnosis, EEG band oscillations as indicators of hypnotic states, alterations in EEG functional connectivity during hypnosis and wakefulness, drawing critical conclusions, and suggesting future research directions. The reviewed functional connectivity findings support the notion that disruptions in the available integration between different components of the executive control network during hypnosis may correspond to altered subjective appraisals of the agency during the hypnotic response, as per dissociated and cold control theories of hypnosis. A promising exploration avenue involves investigating how frontal lobes' neurochemical and aperiodic components of the EEG activity at waking-rest are linked to individual differences in hypnotizability. Future studies investigating the effects of hypnosis on brain function should prioritize examining distinctive activation patterns across various neural networks.

Assessing responsiveness to direct verbal suggestions in depersonalization-derealization disorder

The dissociative disorders and germane conditions are reliably characterized by elevated responsiveness to direct verbal suggestions. However, it remains unclear whether atypical responsiveness to suggestion is similarly present in depersonalization-derealization disorder (DDD). 55 DDD patients and 36 healthy controls completed a standardised behavioural measure of direct verbal suggestibility that includes a correction for compliant responding (BSS-C), and psychometric measures of depersonalization-derealization (CDS), mindfulness (FFMQ), imagery vividness (VVIQ), and anxiety (GAD-7). Relative to controls, patients did not exhibit elevated suggestibility (g = 0.26, BF₁₀ = .11) but displayed significantly lower mindfulness (g = 1.38), and imagery vividness (g = 0.63), and significantly greater anxiety (g = 1.39). Although suggestibility did not correlate with severity of depersonalization-derealization symptoms in controls, r = -.03 [95% CI: -.36, .30], there was a weak tendency for a positive association in patients, r = .25, [95% CI: -.03, .48]. Exploratory analyses revealed that patients with more severe anomalous bodily experiences were also more responsive to suggestion, an effect not seen in controls. This study demonstrates that DDD is not characterized by elevated responsiveness to direct verbal suggestions. These results have implications for the aetiology and treatment of this condition, as well as its classification as a dissociative disorder in psychiatric nosology.

Hypnotic suggestibility in dissociative and related disorders: A meta-analysis

Elevated responsiveness to verbal suggestions is hypothesized to represent a predisposing factor for dissociative disorders (DDs) and related conditions. However, the magnitude of this effect has not been estimated in these populations nor has the potential moderating influence of methodological limitations on effect size variability across studies. This study assessed whether patients with DDs, trauma- and stressor-related disorders (TSDs), and functional neurological disorder (FND) display elevated hypnotic suggestibility. A systematic literature search identified 20 datasets. A random-effects meta-analysis revealed that patients displayed greater hypnotic suggestibility than controls, Hedges's g=0.92 [0.66, 1.18]. This effect was observed in all subgroups but was most pronounced in the DDs. Although there was some evidence for publication bias, a bias-corrected estimate of the group effect remained significant, g=0.57 [0.30, 0.85]. Moderation analyses did not yield evidence for a link between effect sizes and methodological limitations. These results demonstrate that DDs and related conditions are characterized by elevated hypnotic suggestibility and have implications for the mechanisms, risk factors, and treatment of dissociative psychopathology.

Hypnotic predictors of agency: Responsiveness to specific suggestions in hypnosis is associated with involuntariness in fibromyalgia

Hypnosis is associated with alterations in the sense of agency which can play a role in its utilization as a nonpharmacological option for pain management. The goal of the current study was to examine the relationships between responsiveness to suggestions in hypnosis and alterations of the sense of agency among patients with fibromyalgia. Ninety-eight participants with fibromyalgia underwent two hypnotizability assessments followed by the Sense of Agency Rating Scale. Clinical pain measures were also collected. Involuntariness was predicted by responsiveness to control, ideomotor, and dissociation suggestions. Effortlessness was predicted by responsiveness to control and ideomotor suggestions, and age. Hypnotizability was associated with main clinical pain outcomes, but agency alterations were not. Results suggest a shared mechanism between responsiveness to specific suggestions and the sense of agency in hypnosis. We discuss theoretical and clinical implications for pain management and the need for further research.

Suggestibility in functional neurological disorder: a meta-analysis

OBJECTIVE

Responsiveness to direct verbal suggestions (suggestibility) has long been hypothesised to represent a predisposing factor for functional neurological disorder (FND) but previous research has yielded conflicting results. The aim of this study was to quantitatively evaluate whether patients with FND display elevated suggestibility relative to controls via meta-analysis.

METHODS

Four electronic databases were searched in November 2019, with the search updated in April 2020, for original studies assessing suggestibility using standardised behavioural scales or suggestive symptom induction protocols in patients with FND (including somatisation disorder) and controls. The meta-analysis followed Cochrane, Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Meta-analyses Of Observational Studies in Epidemiology (MOOSE) guidelines. Data extraction and study quality coding were performed by two independent reviewers. Standardised suggestibility scores and responsiveness to symptom induction protocols were used to calculate standardised mean differences (SMDs) between groups.

RESULTS

Of 26 643 search results, 19 articles presenting 11 standardised suggestibility data sets (FND: n=316; control: n=360) and 11 symptom suggestibility data sets (FND: n=1285; control: n=1409) were included in random-effect meta-analyses. Meta-analyses revealed that patients with FND displayed greater suggestibility than controls on standardised behavioural scales (SMD, 0.48 (95% C, 0.15 to 0.81)) and greater responsiveness to suggestive symptom induction (SMD, 1.39 (95% CI 0.92 to 1.86)). Moderation analyses presented mixed evidence regarding the extent to which effect sizes covaried with methodological differences across studies. No evidence of publication bias was found.

CONCLUSIONS

These results corroborate the hypothesis that FND is characterised by heightened responsiveness to verbal suggestion. Atypical suggestibility may confer risk for FND and be a cognitive marker that can inform diagnosis and treatment of this condition.

Multicomponent Theories of Hypnotizability: History and Prospects

This review addresses multicomponent theories of hypnotizability by focusing on 3 important exemplars from the history of hypnosis research: E. R. Hilgard's (1965) Hypnotic susceptibility; R. E. Shor's (1962) Three dimensions of hypnotic depth; and T.X. Barber's (1999) A comprehensive three-dimensional theory of hypnosis. Taken together, they illustrate the variety of hypnotic phenomena examined in research - overt responses, subjective experiences, and underlying processes - and the ways in which evidence about each has implied the existence of multiple underlying components. Particularly highlighted are the different ways in which the theories conceptualize the joint contribution of multiple individual differences. Also covered is relevant later work by other researchers as well as important issues remaining to be resolved.

A Critical Review of Standardized Measures of Hypnotic Suggestibility

The most well-established finding gleaned from decades of experimental hypnosis research is that individuals display marked variability in responsiveness to hypnotic suggestions. Insofar as this variability impacts both treatment outcome in therapeutic applications of hypnosis as well as responsiveness to suggestions in experimental contexts, it is imperative that clinicians and researchers use robust measures of hypnotic suggestibility. The current paper critically evaluates contemporary measures of hypnotic suggestibility. After reviewing the most widely used measures, we identify multiple properties of these instruments that result in the loss of valuable information, including binary scoring and single-trial sampling, and hinder their utility, such as the inclusion of suboptimal suggestion content. The scales are not well-suited for contemporary research questions and have outlived their usefulness. We conclude by outlining ways in which the measurement of hypnotic suggestibility can be advanced.

Anomalous experiences are more prevalent among highly suggestible individuals who are also highly dissociative

Introduction: Predictive coding models propose that high hypnotic suggestibility confers a predisposition to hallucinate due to an elevated propensity to weight perceptual beliefs (priors) over sensory evidence. Multiple lines of research corroborate this prediction and demonstrate a link between hypnotic suggestibility and proneness to anomalous perceptual states. However, such effects might be moderated by dissociative tendencies, which seem to account for heterogeneity in high hypnotic suggestibility. We tested the prediction that the prevalence of anomalous experiences would be greater among highly suggestible individuals who are also highly dissociative.Methods: We compared high and low dissociative highly suggestible participants and low suggestible controls on multiple psychometric measures of anomalous experiences.Results: High dissociative highly suggestible participants reliably reported greater anomalous experiences than low dissociative highly suggestible participants and low suggestible controls, who did not significantly differ from each other.Conclusions: These results suggest a greater predisposition to experience anomalous perceptual states among high dissociative highly suggestible individuals.

Trauma and anxious attachment influence the relationship between suggestibility and dissociation: a moderated-moderation analysis

INTRODUCTION

Hypnotic suggestibility is elevated in the dissociative disorders but the relationship between dissociative tendencies and suggestibility in the general population seems to be constrained by additional factors. The diathesis-stress (DS) model stipulates that suggestibility interacts with trauma exposure to augment the propensity for dissociative states whereas the dual pathway to suggestibility (DPS) model proposes two developmental routes involving either dissociation preceded by trauma, or a healthy cognitive profile characterised by superior imagination.

METHODS

This study sought to discriminate between these partially competing accounts and further considered the moderating role of anxious attachment. 209 participants completed psychometric measures of dissociative tendencies, trauma, and attachment, and a behavioural measure of suggestibility.

RESULTS

In support of the DS model, trauma moderated the relationship between suggestibility and dissociation and, as predicted by the DPS model, dissociation moderated the relationship between trauma and suggestibility. Anxious attachment additionally moderated both effects. Model comparisons indicated that the DS model consistently provided a superior fit to the data. Further analyses showed that secure attachment independently predicted suggestibility, thereby supporting the non-dissociative pathway in the DPS model.

CONCLUSIONS

These results suggest that high suggestibility confers vulnerability to dissociative states in individuals exposed to trauma and displaying an anxious attachment style.

THE ROLES OF RESPONSE EXPECTANCIES, BASELINE EXPERIENCES, AND HYPNOTIZABILITY IN SPONTANEOUS HYPNOTIC EXPERIENCES

This study evaluated factors underlying individual differences in spontaneous (unsuggested) experiences during hypnosis. Participants varying in hypnotizability (low, medium, and high) completed a questionnaire about various dimensions of consciousness they would expect to experience at the "deepest level of hypnosis" (expectancy), an eyes-closed resting condition (baseline), and their actual experiences during "neutral hypnosis" (hypnosis). Responses during hypnosis were characterized by higher scores in dimensions related to alterations in conscious experience, affect, and imagery, and lower scores in rationality and agency. Only highs and mediums evinced increases in altered experience and body image. Across conditions, highs reported greater alterations in time experience and lower self-awareness than other groups. Participants overall tended to overestimate the changes they would experience in hypnosis. Baseline and hypnosis correlated in various dimensions, including affect, arousal, and internal dialogue. After controlling for baseline scores and hypnotizability, expectancies correlated with some dimensions having to do with alterations in consciousness. In sum, spontaneous experiences during hypnosis are driven by response expectancies, hypnotizability, and baseline experiences, which show differential effects.

Reconsidering the autohypnotic model of the dissociative disorders

The dissociative disorders field and the hypnosis field currently reject the autohypnotic model of the dissociative disorders, largely because many correlational studies have shown hypnotizability and dissociation to be minimally related (r = .12). Curiously, it is also widely accepted that dissociative patients are highly hypnotizable. If dissociative patients are highly hypnotizable because only highly hypnotizable individuals can develop a dissociative disorder - as the author proposes - then the methodology of correlational studies of hypnotizability and dissociation in random clinical and community samples would necessarily be constitutively unable to detect, and statistically unable to reflect, that fact. That is, the autohypnotic, dissociative distancing of that small subset of highly hypnotizable individuals who repeatedly encountered intolerable circumstances is statistically lost among the data of (1) the highly hypnotizable subjects who do not dissociate and (2) subjects (of all levels of hypnotizability) who manifest other kinds of dissociation. The author proposes that, when highly hypnotizable individuals repeatedly engage in autohypnotic distancing from intolerable circumstances, they develop an overlearned, highly-motivated, automatized pattern of dissociative self-protection (i.e., a dissociative disorder). The author urges that theorists of hypnosis and the dissociative disorders explicitly include in their theories (a) the trait of high hypnotizability, (b) the phenomena of autohypnosis, and (c) the manifestations of systematized, autohypnotic pathology. Said differently, the author is suggesting that autohypnosis and autohypnotic pathology are unacknowledged nodes in the nomothetic networks of both hypnosis and dissociation.

Is high hypnotizability a necessary diathesis for pathological dissociation?

During the 19th century, high hypnotizability was considered to be a form of psychopathology that was inseparable from hysteria. Today, hypnotizability is considered to be a normal trait that has no meaningful relationship with psychopathology. Psychiatric patients generally manifest medium to low hypnotizability. Nevertheless, several psychiatric diagnoses are marked by an unexpectedly large proportion of patients with high hypnotizability. This is especially true of the diagnostic categories that were subsumed by the 19th-century concept of hysteria: dissociative identity disorder, somatization disorder, and complex conversion disorders. These hysteria-related modern diagnoses are also highly dissociative. A review and analysis of the literature regarding the relationship between hypnotizability and dissociation indicates that high hypnotizability is almost certainly a necessary diathesis for the development of a severe dissociative disorder. Such a diathesis has significant implications for (a) the psychiatric nosologies of the American Psychiatric Association and the World Health Organization, (b) the hypnosis field, and (c) the etiology and construct validity of dissociative identity disorder and other severe dissociative disorders. Specifically, the dissociative disorders (excepting depersonalization disorder, which is not classified as a dissociative disorder by the World Health Organization) are manifestations of hypnotic pathology.

Nuances and Uncertainties Regarding Hypnotic Inductions: Toward a Theoretically Informed Praxis

Although most definitions of hypnosis consider inductions as the initial stage in a hypnosis protocol, knowledge of inductions remains poor and uninformed by recent developments in theory and research. It is frequently argued that inductions play a critical role in hypnotic responding or, by contrast, are largely interchangeable and unimportant. Drawing on the literature on suggestibility, spontaneous phenomenology, neurophysiology, and cognition, this article argues that the value of inductions, as well as the potential value of inductions, is more nuanced and uncertain. Certain components of standard inductions appear to be efficacious in enhancing suggestibility, whereas others do not have any clear benefits. The impact of inductions on suggestibility seems to vary across suggestions and modes of assessment with the sources of this variability being unknown. Considering these effects, and the broader impact of inductions on spontaneous conscious states and cognition, through the lens of heterogeneity in high hypnotic suggestibility and componential models of hypnotic suggestibility may offer novel research avenues in this area. The article concludes by arguing for the practical and theory-driven optimization of inductions.