“False dichotomies” and “FND fundamentalists”: an international mixed methods exploration of clinician and rheumatology patients’ views and experiences of functional neurological disorder (FND) co-diagnoses

Abstract Functional neurological disorder (FND) presentations include limb weakness, tremors, non-epileptic seizures, and sensory symptoms. FND can present diagnostic challenges in systemic autoimmune rheumatic diseases (SARDs) due to overlapping neuropsychiatric symptoms. Evidence regarding its role and impact as a potential co-diagnosis in SARDs remains limited. Mixed methods data from international surveys and interviews were used to explore FND as a co-diagnosis in SARDs. Quantitative analyses included group comparisons using t-tests, ANOVA and Kruskal-Wallis tests as appropriate. Qualitative data were analysed thematically. Survey responses (N = 1853 patients, N = 400 clinicians, N = 463 general population) and in-depth interviews (N = 19 patients, N = 27 clinicians), indicated substantial variation in perspectives. Patients’ agreement with their co-diagnoses was higher for depression (86%) than for FND (30%). Participants described experiences suggestive of misattribution in both directions and perceived variation in diagnostic attribution between clinicians. Communication of an FND co-diagnosis varied; when interpreted as implying symptom controllability, this was associated with increased distress and reduced acceptance. Clinicians (72.1%) were significantly more likely than patients (50.2%) and the general population (47.9%) to state that mental health symptoms were considered more acceptable/less stigmatised if they were from the direct effects of the systemic disease (Welch’s F(2647) = 135.006), p < 0.01. Clinicians often used dualistic categorisations of symptoms (e.g., functional versus “organic”). Other clinicians considered dualism particularly unhelpful in SARDs due to the multiplicity, complexity and inter-relatedness of symptoms and aetiologies. FND as a co-diagnosis in SARDs is variably understood and applied, with differing levels of clinician agreement and patient acceptance. Clear, patient-centred explanations of diagnostic attribution, including how symptoms are interpreted and how symptoms being attributed to FND differ from SARD symptoms, may improve understanding and acceptance. These findings highlight the need for improved communication, multidisciplinary approaches and holistic care to support patients with complex neuropsychiatric symptoms.