Reduced microbiome alpha diversity in young patients with ADHD.
Prehn-Kristensen A, Zimmermann A, Tittmann L, Lieb W, Schreiber S, Baving L, Fischer A
PLoS One. 2018. doi: 10.1371/journal.pone.0200728
COMMENT: Attention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed psychiatric diseases in childhood and adolescence. ADHD is characterized by symptoms of hyperactivity, impulsivity and attention problems. Due to recent findings of microbial involvement in other psychiatric disorders like autism and depression, a role of the gut microbiota in ADHD pathogenesis is assumed but has not yet been investigated.
In this study Prehn-Kristensen and coworkers examined the gut microbiota of 14 male ADHD patients (mean age: 11.9 yrs.) and 17 male controls (mean age: 13.1 yrs.) via next generation sequencing of 16S rDNA and analyzed for diversity and biomarkers. They found that the microbial diversity (alpha diversity) was significantly decreased in ADHD patients compared to controls (pShannon = 0.036) and that the composition differed significantly between patients and controls (pANOSIM = 0.033, pADONIS = 0.006, pbetadisper = 0.002).
In detail, the bacterial family Prevotellacae was associated with controls, while patients with ADHD showed elevated levels of Bacteroidaceae, and both Neisseriaceae and some Neisseria species were found as possible biomarkers for juvenile ADHD.
A limitation of the study is the concomitant medication: Ten of 14 patients had taken methylphenidate (MPH), the first-line treatment of ADHD, for more than one year. Another limitation is the small sample size of 14 patients and 17 controls. Studies with larger cohorts are required not only to replicate our findings in a medication-controlled sample but also to investigate possible differences in alpha diversity between subtypes of ADHD. Moreover, including females is mandatory to investigate possible gender effects as indicated by the parental microbiome.
According to the author's conclusion:
Taking the small sample size and the concomitant medication into account, our findings support the hypothesis of an ADHD-specific microbiota. We suggest that the genus Neisseria and elevated levels of Bacteroides spec. are associated with juvenile ADHD.