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

A global neuronal workspace model of functional neurological disorders

We introduce here a general model of Functional Neurological Disorders based on the following hypothesis: a Functional Neurological Disorder could correspond to a consciously initiated voluntary top-down process causing involuntary lasting consequences that are consciously experienced and subjectively interpreted by the patient as involuntary. We develop this central hypothesis according to Global Neuronal Workspace theory of consciousness, that is particularly suited to describe interactions between conscious and non-conscious cognitive processes. We then present a list of predictions defining a research program aimed at empirically testing their validity. Finally, this general model leads us to reinterpret the long-debated links between hypnotic suggestion and functional neurological disorders. Driven by both scientific and therapeutic goals, this theoretical paper aims at bringing closer the psychiatric and neurological worlds of functional neurological disorders with the latest developments of cognitive neuroscience of consciousness.

Hypnosis and suggestion as interventions for functional neurological disorder: A systematic review

OBJECTIVE

Functional neurological disorder (FND) involves the presence of neurological symptoms that cannot be explained by neurological disease. FND has long been linked to hypnosis and suggestion, both of which have been used as treatments. Given ongoing interest, this review examined evidence for the efficacy of hypnosis and suggestion as treatment interventions for FND.

METHOD

A systematic search of bibliographic databases was conducted to identify group studies published over the last hundred years. No restrictions were placed on study design, language, or clinical setting. Two reviewers independently assessed papers for inclusion, extracted data, and rated study quality.

RESULTS

The search identified 35 studies, including 5 randomised controlled trials, 2 non-randomised trials, and 28 pre-post studies. Of 1584 patients receiving either intervention, 1379 (87%) showed significant improvements, including many who demonstrated resolution of their symptoms in the short-term. Given the heterogeneity of interventions and limitations in study quality overall, more formal quantitative synthesis was not possible.

CONCLUSIONS

The findings highlight longstanding and ongoing interest in using hypnosis and suggestion as interventions for FND. While the findings appear promising, limitations in the evidence base, reflecting limitations in FND research more broadly, prevent definitive recommendations. Further research seems warranted given these supportive findings.

Hypnotic analgesia in chronic pain: role of psychopathology and alexithymia

Although the belief that hypnotizability is a mental dysfunction has been refuted over time, there is still research today that seeks to explore and clarify this preconception. The results of recent research indicate that, on the contrary, greater psychopathology is more frequent in subjects with low hypnotic susceptibility. Using the Stanford Hypnotic Susceptibility Scale type A (SHSS-A) for hypnotizability, Symptom Checklist-Revised (SCL-90-R) for psychopathology, and the Somatosensory Amplification Scale (SSAS) and Toronto Alexithymia Scale (TAS-20) for psychosomatic dimensions, we found no relationship between baseline psychopathology, alexithymia and hypnotizability in 69 subjects with chronic pain in this retrospective observational study. Psychopathology did not affect the 2-month outcomes of hypnotic suggestions for pain in terms of either pain (assess using Italian Pain Questionnaire), anxiety or depression (assessed through Hospital Anxiety and Depression Scale) scores. Furthermore, i) no relationships were found between hypnotizability and degree of either psychopathology or alexithymia, definitively eliminating any doubts about the belief that hypnosis is a mental dysfunction; ii) only single hypnotic phenomena (SHSS-A) could be linked to some psychopathological dimensions; iii) analgesia suggestions also acted on anxiety and depression; and iv) the use of hypnotic suggestions for analgesia revealed a close relationship between improvements in sensorial and evaluative dimensions of pain and mitigation of anxiety. Hypnosis thereby seems to be a powerful tool in psychosomatic medicine whose effects on mind and body are inextricably linked.

Absorption and dissociation mediate the relationship between direct verbal suggestibility and impulsivity/compulsivity

Direct verbal suggestibility refers to the capacity for an individual to experience perceptual, motor, affective and cognitive changes in response to verbal suggestions. Suggestibility is characterized by pronounced, yet reliable, inter-individual differences. Previous research and theoretical considerations suggest that greater impulsivity and compulsivity is associated to higher suggestibility, but the characteristics and mediating factors of this association are poorly understood. Using established psychometric measures in an online sample, we found positive correlations between the domain comprising impulsivity, compulsivity and behavioural activation, and the domain of suggestibility, dissociation and absorption. We also observed that dissociation and absorption mediated the link between suggestibility and impulsivity, and between suggestibility and behavioural activation, respectively. These results confirm the positive link between suggestibility and the impulsivity/compulsivity domain and shed new light on the characterisation of traits associated with suggestibility.

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.