Abstract

Background Recent studies reveal increasing interest in the link between Autism Spectrum Disorder (ASD) and Functional Neurological Disorder (FND), prompting a systematic review and meta-analysis of their co-occurrence. Method The review covered a comprehensive literature search across multiple databases up to November 2024, focusing on peer-reviewed studies of ASD and FND co-occurrence. Twenty-four studies qualified for inclusion. Results The study included 11,324 participants, predominantly female (73.4%). It estimated the proportion of ASD in FND populations to be 0.10 (95% CI: 0.07–0.15), with significant heterogeneity (I² = 97%, p < 0.01). Subgroup analysis showed variation among different age groups and diagnoses. The proportion of ASD was 0.09 in adults and 0.10 in children with FND, 0.15 in adults and 0.19 in children with Functional Tic-Like Behaviours (FTLB), and 0.07 in children with Functional Seizures (FS). Conclusion Many studies have reported the co-occurrence of ASD in FND, suggesting a higher-than-expected rate of 10%. Emerging themes exploring the overlapping determinants of FND and ASD, are discussed. However, the significance of this correlation and the overlapping determinants that might explain it, require further research due to the heterogeneity in methodologies, settings, conditions studied and findings. The presence of publication bias warrants cautious interpretation of the results.