**Stephanie Bull-Larsen and M. Hasan Mohajeri \***

Institute of Anatomy, Department of medicine, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland; stephanie.bull-larsen@uzh.ch

**\*** Correspondence: mhasan.mohajeri@uzh.ch; Tel.: +41-79-938-1203

Received: 15 October 2019; Accepted: 13 November 2019; Published: 17 November 2019

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