Comorbidity rates of autism spectrum disorder and functional neurological disorders: A systematic review, meta-analysis of proportions and qualitative synthesis

Abstract

This study evaluated the comorbidity rates of autism spectrum disorder (ASD) with functional neurological disorders (FNDs). A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A subset of data was suitable for meta-analysis of proportions. Studies which assessed either the prevalence of ASD in patients with FNDs, or the prevalence of FNDs in patients with ASD were considered. Critical appraisal was conducted using Joanna Briggs Institute Critical Appraisal Tools. Fourteen studies met the inclusion criteria. Three cross-sectional studies which reported the comorbidity of ASD among children presenting with functional seizures met inclusion for meta-analysis. The pooled comorbidity rate of ASD in this group was 10.26% [3.92, 18.95], with an I2 value of 81%, indicating significant heterogeneity between studies. Most included studies ( n = 5) reported on the rates of Somatic Symptom Disorders in adults with ASD. Comorbidity rates were also reported for ASD with Functional Motor Disorders and for mixed FND cohorts. Critical appraisal indicated that studies were underpowered, did not match cases with controls and failed to account for confounding factors. Identifying ASD and FND comorbidity may guide treatment options and reduce the risks of unnecessary medical investigations. Lay abstract Autism spectrum disorder (ASD) and functional neurological disorders (FND) are relatively common conditions, and there has been recent interest in the overlap between them. Both conditions share core features of alexithymia, impaired interoception and deficits in attentional focus. To date, relatively little is known about the comorbidity rates between ASD and FND. This is the first meta-analysis and qualitative synthesis on the subject. We found that around 10% of children presenting with functional seizures have a comorbid ASD diagnosis. People with ASD are more likely than the neurotypical population to have functional somatic disorders, and there is also evidence that ASD rates are higher for other FNDs such as functional motor disorders. Since FND comes with risks of unnecessary medical procedures and investigations, it is important to recognize the potential for people with ASD to have an FND comorbidity.