Abstract
Objective Responsiveness to direct verbal suggestions (suggestibility) has long been hypothesized 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 FND patients 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 standardized behavioural scales or suggestive symptom induction protocols in FND (including somatization disorder) patients and controls. The metaanalysis followed Cochrane, PRISMA, and MOOSE guidelines. Data extraction and study quality coding were performed by two independent reviewers. Standardized suggestibility scores and responsiveness to symptom induction protocols were used to calculate standardized mean differences (SMDs) between groups.
Results Of 26,643 search results, 19 articles presenting 11 standardized suggestibility datasets (FND: n=316; control: n=360) and 11 symptom suggestibility datasets (FND: n=1285; control: n=1409) were included in random-effects meta-analyses. Meta-analyses revealed that FND patients displayed greater suggestibility than controls on standardized behavioural scales (SMD, 0.48 [95% CI, 0.15, 0.81]) and greater responsiveness to suggestive symptom induction (SMD, 1.39 [95% CI, 0.92, 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 characterized 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.
Methods Four electronic databases were searched in November 2019, with the search updated in April 2020, for original studies assessing suggestibility using standardized behavioural scales or suggestive symptom induction protocols in FND (including somatization disorder) patients and controls. The metaanalysis followed Cochrane, PRISMA, and MOOSE guidelines. Data extraction and study quality coding were performed by two independent reviewers. Standardized suggestibility scores and responsiveness to symptom induction protocols were used to calculate standardized mean differences (SMDs) between groups.
Results Of 26,643 search results, 19 articles presenting 11 standardized suggestibility datasets (FND: n=316; control: n=360) and 11 symptom suggestibility datasets (FND: n=1285; control: n=1409) were included in random-effects meta-analyses. Meta-analyses revealed that FND patients displayed greater suggestibility than controls on standardized behavioural scales (SMD, 0.48 [95% CI, 0.15, 0.81]) and greater responsiveness to suggestive symptom induction (SMD, 1.39 [95% CI, 0.92, 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 characterized 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.
| Original language | English |
|---|---|
| Journal | Journal of Neurology, Neurosurgery and Psychiatry |
| Publication status | Accepted/In press - 22 Sept 2020 |