New research suggests that the microbial composition of the gut may influence a child’s susceptibility to attention deficit hyperactivity disorder (ADHD). A recent study published in the Journal of Child Psychology and Psychiatry shows that children with ADHD have higher levels of certain fungi and lower levels of other species in their gut microbiome compared to healthy controls.
The human gastrointestinal tract contains a large population of microorganisms, including bacteria, viruses, and fungi. The study analysed faecal samples from 35 children with ADHD and 35 healthy controls. The samples from children with ADHD showed an increased abundance of Candida albicans, a species that can cause a “leaky gut” by increasing the permeability of cells that line the intestine. This could potentially allow bacteria into the bloodstream, causing inflammation throughout the body and brain.
The researchers explained that the human body is home to a complex and diverse microbial ecosystem, and findings from this study suggest that dysbiosis of the fungal mycobiome in ADHD can influence patient health.
The Institutional Review Board (IRB) at Chang Gung Memorial Hospital in Taiwan approved the research protocol, and the study protocols were explained to both the children and their parents/guardians. Appendix S1 demonstrates the flow chart of the study design and procedure.
To participate in the study, children with ADHD were recruited from the outpatient clinic of the Department of Child Psychiatry at Chang Gung Children’s Hospital. The inclusion criteria were a clinical diagnosis of ADHD based on the criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), between 6 and 12 years old, and a drug-naive state for ADHD. The exclusion criteria were having major neuropsychiatric diseases other than ADHD, including intellectual disabilities, autism spectrum disorder (ASD), major depressive disorders, bipolar disorders, psychotic disorders, or substance use disorders, having any major physical illnesses such as epilepsy, severe neurological or gastrointestinal disorders, and being a vegetarian or taking any probiotics or antibiotics during the recruitment period.
Healthy control children were recruited from local communities near the hospital. The inclusion criteria were children without ADHD, aged between 6 and 12 years, free from major neuropsychiatric or medical diseases, and non-vegetarians or currently taking no probiotics or antibiotics.
The researchers collected DNA from faecal samples of all participants to sequence and analyse the ITS (internal transcribed spacer) gene. The average number of raw paired reads per sample obtained from ITS-based sequencing was 143,808 for ADHD patients and 118,267 for healthy controls. After filtering the qualified reads, the average number of quality-filtered reads per sample was 93,728 for ADHD patients and 74,343 for healthy controls. The results showed that the sequencing reads were enough to represent most of the fungal community.
The diversity of the fungal community was assessed using alpha diversity and beta diversity in ADHD. The alpha diversity was presented as three indexes: “chao1” estimates the species abundance; “observed species” estimate the number of unique OTUs (operational taxonomic units) found in each sample and the “Shannon index” accounts for both species richness and evenness. No significant difference in the diversity indices observed species, Shannon index, Chao1 index, and PD whole tree between healthy controls and ADHD patients. The beta diversity reflects the difference in fungal community composition between the ADHD and control groups. A principal coordinates analysis (PCoA) plot indicated that the gut fungal community in ADHD patients is significantly different from that identified in the healthy controls.
The gut fungal profiling from healthy controls and ADHD revealed a total of three phyla, of which three accounted for 99% of the fungal. In the healthy controls, Ascomycota was the dominant phylum, followed by Basidiomycota and Mucoromycota. The abundance of Ascomycota was significantly higher in the ADHD group than in the healthy controls, while the abundance of Basidiomycota was significantly lower in the ADHD group than in the healthy controls. The relative abundances of gut fungal distribution at the class, order, and family levels between children with ADHD and healthy controls were also shown.
The researchers concluded that the abundance of Ascomycota at the phylum level and the abundance of Candida at the genus level were identified as gut fungal markers of ADHD. The impact of Candida on barrier function (intestinal permeability) was observed in an in vitro study. The study suggests that dysbiosis of the fungal mycobiome in ADHD can influence patient health.
The ADHD group showed lower average height, body weight, and performance in WISC-IV (full-scale intelligence quotient, perceptual reasoning index, working memory index, and processing speed index) compared to the control group. In addition, patients with ADHD exhibited greater severity in ADHD symptoms from the ratings of parents and teachers and worse performance of omission error in CPT3 compared to the healthy controls.
The findings from this study provide new insights into the role of the gut microbiome in the development of ADHD. While more research is needed to fully understand the complex relationship between the gut microbiome and ADHD, this study opens up new avenues for the development of novel therapies for the disorder.
The researchers explained that these findings have significant implications for the treatment of ADHD. If we can manipulate the gut microbiome in children with ADHD, we may be able to improve their symptoms and quality of life.
The study also has wider implications for the field of psychiatry and highlights the importance of considering the gut-brain axis in the diagnosis and treatment of mental health disorders. While previous studies have focused on the role of gut bacteria in mental health, this study suggests that fungi may also play an important role.
This study provides new evidence to suggest that the microbial composition of the gut may affect a child’s susceptibility to ADHD. The findings have significant implications for the treatment and management of the disorder and highlight the importance of considering the gut-brain axis in mental health research. Further studies are needed to fully understand the complex relationship between the gut microbiome and ADHD and to explore the potential for novel therapies targeting the gut microbiome.