The Potential Influence of the Bacterial Microbiome on the Development and Progression of ADHD

Abstract

The latest research cumulates staggering information about the correlation between the microbiota-gut-brain axis and neurodevelopmental disorders. This review aims to shed light on the potential influence of the microbiome on the development of the most prevalent neurodevelopmental disease, attention-deficit-hyperactive disorder (ADHD). As the etiology and pathophysiology of ADHD are still unclear, finding viable biomarkers and effective treatment still represent a challenge. Therefore, we focused on factors that have been associated with a higher risk of developing ADHD, while simultaneously influencing the microbial composition. We reviewed the effect of a differing microbial makeup on neurotransmitter concentrations important in the pathophysiology of ADHD. Additionally, we deduced factors that correlate with a high prevalence of ADHD, while simultaneously affecting the gut microbiome, such as emergency c-sections, and premature birth as the former leads to a decrease of the gut microbial diversity and the latter causes neuroprotective Lactobacillus levels to be reduced. Also, we assessed nutritional influences, such as breastfeeding, ingestion of short-chain fatty acids (SCFAs) and polyunsaturated fatty acids (PUFAs) on the host's microbiome and development of ADHD. Finally, we discussed the potential significance of Bifidobacterium as a biomarker for ADHD, the importance of preventing premature birth as prophylaxis and nutrition as a prospective therapeutic measurement against ADHD.

Keywords: ADHD; attention-deficit-hyperactive-disorder; microbiome; microbiota-gut-brain axis.

Figure 1

The most prevalent bacterial phyla in utero and in the GI-tract of humans. This figure represents the dynamic and development of the composition of the microbiome from fetuses in utero until the age of three years, at which point the microbiome gains its stability and consists of mostly four phyla: Proteobacteria, Actinobacteria, Firmicutes, and Bacteroides.

Figure 2

The synthesis pathway from L-phenylalanine to noradrenaline including all its intermediary products. Dopamine acts as an important metabolite for the emotional response and reward system [64].