A comparative study on dietary diversity and gut microbial diversity in children with autism spectrum disorder, attention‐deficit hyperactivity disorder, their neurotypical siblings, and non‐related neurotypical volunteers: a cross‐sectional study

Background Previous research has shown a significant link between gut microbiota in children with autism spectrum disorder (ASD) and attention‐deficit hyperactivity disorder (ADHD). However, much remains unknown because of the heterogeneity of disorders and the potential confounders such as dietary patterns and control group variations. Methods Children aged 6–12 years who had been clinically diagnosed with ASD and/or ADHD, their unaffected neurotypical siblings, and non‐related neurotypical volunteers were recruited cross‐sectionally. The ASD diagnosis was confirmed using the Autism Diagnostic Observation Schedule‐2 (ADOS‐2) in all patients, including those with ADHD. Standardized DNA extraction and sequencing methods were used to compare gut microbial alpha‐diversity among the groups. Dietary diversity was calculated from a standardized dietary questionnaire form. We compared the difference in gut microbiome between patients with ASD and/or ADHD with neurotypical siblings and non‐related neurotypical controls. Results Ninety‐eight subjects were included in the study (18 with ASD, 19 with ADHD, 20 with both ASD and ADHD, 13 neurotypical siblings, and 28 non‐related neurotypical controls). The alpha‐diversity indices, such as Chao 1 and Shannon index, showed a significant difference between the groups in a Linear mixed‐effect model ( F (4, 93) = 4.539, p = .02), ( F (4, 93) = 3.185, p = .017), respectively. In a post‐hoc pairwise comparison, patients with ASD had lower alpha‐diversity compared with non‐related controls after Bonferroni correction. Dietary diversity shown in Shannon index did not differ among the groups ( F (4, 84) = 1.494, p = .211). Conclusions Our study indicates disorder‐specific microbiome differences in patients with ASD. In future research on gut microbiota in neurodevelopmental disorders, it is necessary to consider the impact of ASD and ADHD co‐occurrence, and strictly control for background information such as diet, to elucidate the gut–microbiota interaction in ASD and ADHD for exploring the potential of therapeutic interventions.