Microbiome - a (FUTURE) marker for the differential diagnosis for autism spectrum disorder and attention-deficit/hyperactivity disorder?

INTRODUCTION: The differential diagnosis between Autism Spectrum Disorder (ASD) and Attention Deficit/Hyperactivity Disorder (ADHD) is often challenging and detrimental to early and timely treatment. Co-current and overlapping symptoms contribute to erode differential diagnostic accuracy, based mainly on clinical assessment supported by standardized instruments and reports from parents and teachers. The microbiota was recently considered a valuable resource in the search for biological markers in neurodevelopmental disorders. OBJECTIVES: Our objective was to examine the published literature in order to clarify the role of the microbiome as a possible differential biomarker between ASD and ADHD. METHODS: Five hundred and sixteen articles were reviewed in order to contextualize the role of Gut- Brain Axis in neurodevelopment and neurodevelopmental disorders, the microbiome as a biomarker and ultimately to unravel microbiome abnormalities reported in patients diagnosed with ASD and/or ADHD. RESULTS: Although gut microbiome appears to be involved in the pathogenesis of ASD with several reports identifying changes in gut populations and functions, a “microbial signature” is still not reached. In ADHD patients, research confirms that the composition and predicted functions of gut microbiome are also altered, but identically controversial results were found. CONCLUSIONS: Future studies are needed to confirm the relationship between the composition and function of the microbiome and the occurrence or presentation of each of the disorders. A specific signature of the microbiota could then constitute itself as a differential biomarker in ASD and ADHD.