Suggestibility in functional neurological disorder: a meta-analysis, 2020, Wieder et al

Andy · Nov 22, 2020

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.
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Paywall, https://jnnp.bmj.com/content/early/2020/11/19/jnnp-2020-323706.full
Sci hub, https://sci-hub.se/10.1136/jnnp-2020-323706

Snow Leopard · Nov 22, 2020

GIGO

Previously referred to as hysteria, and also known as conversion disorder, functional neurological symptom disorder and dissociative neurological symptom disorder, FND has a prevalence of 4–12 per 100 0004 5 and is found in 16% of neurology outpatients.6 It is associated with considerable diagnostic delays and frequent misdiagnosis,7 which add to the already significant psychological, social and economic impact of the condition.8
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FND has long been hypothesised to be characterised by elevated responsiveness to direct verbal suggestions (suggestibility),9 and suggestion and the expression of functional symptoms have been hypothesised to recruit overlapping mechanisms.10 Suggestibility is theorised to confer vulnerability for FND11 through aberrant meta-awareness of intentions,12–15 the capacity for suggestions to trigger automatised behavioural routines or mental representations11 and/or a tendency to form precise (symptom) priors that override motor and perceptual systems.16 17 The use of suggestion to provoke FND symptoms is widely used to aid diagnosis18 19 and functional symptoms are responsive to suggestion-based treatments such as hypnosis and placebo.20
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Mhmm.

Hutan · Nov 22, 2020

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.
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Assuming the scales etc really measured suggestibility (which is a big assumption), I think this might say more about the nature of people willing to participate in these studies and be labeled as having 'previously referred to as hysteria, and also known as conversion disorder, functional neurological symptom disorder and dissociative neurological symptom disorder', than anything about the wider 'FND' patient population.

Hutan · Nov 22, 2020

No evidence of publication bias was found.
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How many bottom drawers did they look in though?

Hutan · Nov 22, 2020

Insofar as suggestibility is a positive predictor of outcome with suggestion-based treatments,52 these results also support greater incorporation of suggestion techniques in treatment protocols, which show promising results in randomised controlled trials.20

However, they also highlight the need to control for suggestion, or consider its role, in diagnostic and treatment procedures, particularly those that evoke strong response expectancies.46
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Suggestibility in functional neurological disorder: a meta-analysis, 2020, Wieder et al

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Suggestibility in functional neurological disorder: a meta-analysis, 2020, Wieder et al

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