Cognitive performance in functional neurological disorder: A systematic review and meta-analysis

Background: Cognitive complaints are common in functional neurological disorder (FND), but it is unclear whether objective neurocognitive deficits are present. This systematic review summarised validated/standardised cognitive test performance in FND samples across cognitive domains. Methods: Embase, PsycInfo and MEDLINE were searched from inception to 15th May 2023, combining terms for FND and cognitive domains (e.g., attention, memory, executive functioning). Studies included a range of FND phenotypes (seizures, motor, cognitive disorder, mixed), compared to healthy or clinical controls. Risk of bias was assessed with the modified Newcastle-Ottawa Scale and a qualitative synthesis/narrative review of cognitive performance in FND was conducted. Test performance scores were extracted, and random-effects meta-analyses were run where appropriate. This review was registered on PROSPERO, CRD42023423139.Results: Fifty-six studies including2260 individuals with FND were eligible. Although evidence for some impairments emerged across domains of executive functioning, attention, memory, and psychomotor/processing speed, this was inconsistent across studies and FND phenotypes. Common confounds included group differences in demographics, medication, and intellectual functioning. Only 24% of studies objectively assessed performance validity. Meta-analyses revealed higher scores on tests of naming (g=.67, 95%CI [.50, .84]) and long-term memory (g=.43, 95%CI [.13, .74]) in functional seizures versus epilepsy, but no significant differences in working (g=-.08, 95%CI [-.44, .29]) or immediate (g=.25, 95%CI [-.02, .53]) memory and cognitive flexibility (g=-.01, 95%CI [-.29, .28]). Conclusions: There is mixed evidence for objective cognitive deficits in FND. Future research should control for confounds, include tests of performance validity, and assess relationships between objective and subjective neurocognitive functioning.