The Co-Occurrence of Postural Orthostatic Tachycardia and Functional Neurological Disorder: A Meta-Analysis and Narrative Synthesis

Background: Functional Neurological Disorder (FND) and Postural Orthostatic Tachycardia Syndrome (POTS) are both complex, often debilitating conditions that frequently affect young women and involve high symptom burdens and psychiatric comorbidity. Although clinical overlap between these two disorders has long been observed, quantitative evidence assessing their co-occurrence has been lacking. Objective: The aim of this review was to determine the frequency of POTS in patients with FND and FND in patients with POTS through meta-analysis of the available literature, and to describe overlapping putative factors between the two conditions. Methods: A comprehensive literature search was conducted across PubMed and Google Scholar up to April 2025. The meta-analysis was conducted and reported in accordance with PRISMA guidelines. Studies reporting original data on the frequency of POTS in individuals with FND and FND in individuals with POTS were included. Meta-analyses were performed using random-effects models. Quality assessment was conducted using the JBI critical appraisal tools. Evidence relating to overlapping putative factors between POTS and FND was synthesised narratively. Results: From over 37,000 records, 11 studies comprising 1199 participants were included. The pooled proportion of POTS among individuals with FND was 14% (95% CI: 5–26%), with the highest rates seen in those with functional seizures (26%). Substantial heterogeneity (I2 = 94.6%) reflected differences in methodology, age group, setting, and diagnostic criteria. Evidence regarding FND in POTS remains limited. Overlapping putative factors included biopsychosocial predisposing factors, female gender, altered interoception, psychological trauma and stress response, immune dysregulation, neurohumoral factors and comorbidities. Conclusions: The findings suggest that the proportion of POTS among individuals with FND is higher than expected by chance alone. An overview of their overlap highlights potential shared biopsychosocial mechanisms and provides a framework for integrated clinical care. Recognising their co-occurrence and the need for careful differential diagnosis between these conditions may inform screening, diagnosis, and multidisciplinary management strategies. This perspective supports a non-dualistic, neuroscience-based approach and identifies priorities for future research.