Psychological heterogeneity in functional neurological disorders: A systematic review of studies exploring psychopathological sub-types

BACKGROUND: Functional Neurological Disorders (FND) are characterised by distressing neurological symptoms arising from altered brain network functioning rather than structural damage. FND were traditionally conceptualised as homogeneous (conversion) disorders despite the apparent heterogeneity of the condition. OBJECTIVE: In order to aid our understanding of the clinical spectrum of FND, this systematic review explores empirical evidence for psychological patient sub-groups. METHODS: OVID Medline/Embase/PsycINFO, Scopus and WoS were searched from 1980 to September 2025. We used the SURE quality appraisal process and an analytic process involving four steps of narrative synthesis. RESULTS: Of 10,414 articles screened, 13 papers met our inclusion criteria. Six non-exclusive and potentially interacting psychological themes were identified: "emotional dysregulation associated with high distress", "constricted affect with low overt distress", "presence of comorbid mental disorders", "overt traumatisation", "dissociation" and "lower intellectual abilities". CONCLUSIONS: This review confirms that there is an empirical basis for the perception of FND as aetiologically heterogeneous disorders. Six recurring psychological themes, often overlapping and interconnected, were identified. These findings emphasize the necessity of adopting a multidimensional framework for understanding FND. Further empirical validation may allow for FND treatment to be tailored to the specific psychological needs of this diverse patient group.