The Microbiome-Gut-Brain Axis and Resilience to Developing Anxiety or Depression under Stress

Abstract

Episodes of depression and anxiety commonly follow the experience of stress, however not everyone who experiences stress develops a mood disorder. Individuals who are able to experience stress without a negative emotional effect are considered stress resilient. Stress-resilience (and its counterpart stress-susceptibility) are influenced by several psychological and biological factors, including the microbiome-gut-brain axis. Emerging research shows that the gut microbiota can influence mood, and that stress is an important variable in this relationship. Stress alters the gut microbiota and plausibly this could contribute to stress-related changes in mood. Most of the reported research has been conducted using animal models and demonstrates a relationship between gut microbiome and mood. The translational evidence from human clinical studies however is rather limited. In this review we examine the microbiome-gut-brain axis research in relation to stress resilience.

Keywords: anxiety; depression; enteric nervous system; gut microbiota; gut-inflammation; gut-permeability; mood; probiotics; stress; vagus nerve.

Figure 1

The proposed mechanisms of the microbiome-gut-brain axis (MGBA) are complex and intertwined. Emerging research shows that psychological stress interacts not only directly with the brain and mood, but also with many of the MGBA mechanisms thought to contribute to changes in mood with alteration of the gut microbiota. Solid lines indicate strong evidence of an effect, and dotted lines show proposed mechanisms with limited but emerging evidence. Abbreviations: HPA; Hypothalamic-Pituitary-Adrenal.