Dissociation and its biological and clinical associations in functional neurological disorder: systematic review and meta-analysis

Abstract

Background Studies have reported elevated rates of dissociative symptoms and comorbid dissociative disorders in functional neurological disorder (FND); however, a comprehensive review is lacking. Aims To systematically review the severity of dissociative symptoms and prevalence of comorbid dissociative disorders in FND and summarise their biological and clinical associations. Method We searched Embase, PsycInfo and MEDLINE up to June 2021, combining terms for FND and dissociation. Studies were eligible if reporting dissociative symptom scores or rates of comorbid dissociative disorder in FND samples. Risk of bias was appraised using modified Newcastle–Ottawa criteria. The findings were synthesised qualitatively and dissociative symptom scores were included in a meta-analysis (PROSPERO CRD42020173263). Results Seventy-five studies were eligible (FND n = 3940; control n = 3073), most commonly prospective case–control studies (k = 54). Dissociative disorders were frequently comorbid in FND. Psychoform dissociation was elevated in FND compared with healthy (g = 0.90, 95% CI 0.66–1.14, I2 = 70%) and neurological controls (g = 0.56, 95% CI 0.19–0.92, I2 = 67%). Greater psychoform dissociation was observed in FND samples with seizure symptoms versus healthy controls (g = 0.94, 95% CI 0.65–1.22, I2 = 42%) and FND samples with motor symptoms (g = 0.40, 95% CI −0.18 to 1.00, I2 = 54%). Somatoform dissociation was elevated in FND versus healthy controls (g = 1.80, 95% CI 1.25–2.34, I2 = 75%). Dissociation in FND was associated with more severe functional symptoms, worse quality of life and brain alterations. Conclusions Our findings highlight the potential clinical utility of assessing patients with FND for dissociative symptomatology. However, fewer studies investigated FND samples with motor symptoms and heterogeneity between studies and risk of bias were high. Rigorous investigation of the prevalence, features and mechanistic relevance of dissociation in FND is needed.

Factors Influencing Triage to Rehabilitation in Functional Movement Disorder

“…When present, therapeutic strategies include helping patients learn to set boundaries, to identify and prioritize their own emotional needs, and to schedule self‐care. These results emphasize the importance of a holistic approach to triage and treatment in FMD that includes non‐pathological psychological factors, which are important drivers of treatment suitability 24 …”

“…These results emphasize the importance of a holistic approach to triage and treatment in FMD that includes non-pathological psychological factors, which are important drivers of treatment suitability. 24 An interesting observation was that an inability to notice symptom inconsistency was a significant indicator of poor rehabilitation suitability. A key strategy in FMD physiotherapy is helping the patient recognize that periods of normal function can occur, usually when distracted or performing automatic tasks.…”

“…These results emphasize the importance of a holistic approach to triage and treatment in FMD that includes non‐pathological psychological factors, which are important drivers of treatment suitability. 24 …”

Biomarkers of dissociation

“…This themed series also invited systematic reviews and meta-analyses. A review of dissociation and its biological and clinical associations in functional neurological disorder (FND) by Campbell and colleagues 18 might be perceived as controversial, because although FND is currently classified as a dissociative disorder in ICD-11, this conceptualisation is not widely accepted. The findings that dissociation in FND is associated with structural and functional brain alterations, including frontal brain regions, are clinically relevant and support the classification as a dissociative disorder.…”

Interoceptive disruption in functional neurological disorder: a multimodal brain imaging study

“…Functional neurological symptoms are not primarily driven by a discrete structural lesion, but rather reflect abnormal activations within and across several distributed brain networks (Baizabal-Carvallo et al, 2019; Hallett et al, 2022. Core FND and non-motor symptoms (e.g., fatigue, pain, dissociation, depression and anxiety) lead to high disability and impaired quality of life comparable with those observed in other major neuropsychiatric conditions (Campbell et al, 2022; Forejtová et al, 2023). Traditionally, emphasis has been placed on psychophysiological factors such as emotion dysregulation and adverse life experiences as predisposing vulnerabilities and/or acute precipitants in patients with FND (Drane et al, 2020).…”