Relationship Between the Microbiome and Posttraumatic Stress Disorder: A Scope on Pre-Clinical and Human (intervention) Studies

Background
PTSD is a significant health challenge affecting an extensive demographic worldwide. An emerging area of exploration is the influence of the human microbiome on PTSD. Several studies have correlated microbiome imbalances or dysbiosis with mental health disorders, implying potential implications for PTSD via the gut-brain axis, a two-way communication system between our brain and gut. This study provides a comprehensive look at current research on the microbiome-PTSD interplay.

Methods
We conducted a comprehensive scoping review to investigate the relationship between the microbiome and PTSD. Our systematic methodology involved conducting a literature search using the databases; Medline, Embase, and PsychINFO. Both human participants diagnosed with PTSD and preclinical studies using rodent models of PTSD were included. Outcomes of interest encompassed changes in microbiome composition and diversity, measures of the gut-brain axis, and intervention-related metrics.

Results
Our review synthesized studies published between 2016 and 2023. Tools for microbiome analysis were high throughput sequencing such as genome sequencing and 16S ribosomal RNA sequencing, with fecal samples being the major source for microbial community measurement. Observational studies reported significant shifts in microbiome diversity and specific microbial phyla due to stress. Intervention studies, mainly utilizing Mycobacterium vaccae (M. vaccae), showed it could potentially alleviate stress-induced behavioral alterations and promote microbiota stability.

Conclusions
There is a compelling argument for a relationship between PTSD and the microbiome. There is need for extensive (human) studies with larger sample sizes and more diverse study scopes. This holds potential in paving the way towards new avenues of treatment.

Keywords
Microbiome, PTSD - Posttraumatic Stress Disorder, pre-clinical, Clinical