Structured clinical diagnostic assessment reveals autism spectrum disorder in adults with functional neurological disorder.

Emerging evidence suggests a link between Autism Spectrum Disorder (ASD) and Functional Neurological Disorder (FND), underscoring the importance of considering neurodevelopmental traits in neurological care. This study examined the prevalence of clinically probable ASD (CP-ASD) in a specialist FND clinic and explored its associations with symptom presentation, mental health, alexithymia and interoceptive awareness. Sixteen consecutively recruited adults with FND underwent comprehensive ASD assessment, including self-report questionnaires (RAADS-R, AdAS Spectrum), observational interview (ADOS-IV), and evaluation against DSM-5 criteria. Additional validated psychometric measures assessed anxiety (GAD-7), depression (PHQ-9), dissociation (Cambridge Depersonalization Scale, CDS), alexithymia (TAS-20), camouflaging (CAT-Q), and interoceptive sensibility (MAIA-2). Half of the participants (n = 8) met criteria for CP-ASD. Compared with the non-CP-ASD group, the CP-ASD group had a younger age at symptom onset and a longer interval from onset to FND diagnosis. After correction for multiple comparisons, significant group differences remained for anxiety (GAD-7), dissociation (CDS), and camouflaging behaviours (CAT-Q total, Compensation, and Assimilation subscales). Several further differences reached uncorrected significance with large effect sizes, including alexithymia (TAS-20) and the MAIA-2 Not Worrying and Emotional Awareness subscales, but did not survive correction and should be considered exploratory. Among functional symptom types, only sensory symptoms differed, being more prevalent in the CP-ASD group (62.5% vs 12.5%, p =.021), while treatment response did not differ between groups. . These findings suggest that ASD may frequently co-exist with FND but remain under-recognised. Incorporating routine screening and neurodevelopmentally informed care could improve diagnostic accuracy and support more personalised interventions. Larger, adequately powered studies are needed to confirm these preliminary results and to clarify further the role of neurodevelopmental factors in the onset, persistence, and treatment response of FND.