Title: The possible link of gut microbiota Attention-Deficit Hyperactivity Disorder (ADHD)

Abstract

Gut-Brain Axis (GBA) is extensively studied nowadays, especially about its possible link to various neuropsychiatric disorders, one of them being Attention-Deficit Hyperactivity Disorder (ADHD). We reviewed the existing studies analyzing the gut microbiota between human samples in ADHD and health individuals. The literatures were obtained using Google Scholar, Pubmed, and Science Direct databases. The keyword used were “ADHD”, “gut microbiota”, “stool”, “gut”, and “microbiota”. All of the selected studies were case-control study. We found forty-nine bacterium taxa, but for now none of them can explain the precise relationship between ADHD and gut microbiota. Bifidobacterium was found increased in ADHD, but other study stated that this genus was decreased in ADHD with post-micronutrient treatment. This may suggest that micronutrient can modulate the population of Bifidobacterium and improve the behaviour of ADHD patients. Another genus found decreased in ADHD was Dialister, but found to be increased in those consumed medications. Lastly, the abundance of genus Faecalibacteriumwas found lower which may induce over-production of pro-inflammatory cytokines. We can say this because Faecalibacteriumis known for its anti-inflammatory products, whilst ADHD patients tend to have high level of pro-inflammatory cytokines. There were no studies that explain which bacterial taxa correlated most to ADHD. This might occur due to different model and methods in each study. Further study is needed to identify the correlation between gut microbiota and ADHD.