Inflammation, Lifestyle Factors, and the Microbiome-Gut-Brain Axis: Relevance to Depression and Antidepressant Action

Depression is considered a major public health concern, where existing pharmacological treatments are not equally effective across all patients. The pathogenesis of depression involves the interaction of complex biological components, such as the immune system and the microbiota-gut-brain axis. Adjunctive lifestyle-oriented approaches for depression, including physical exercise and special diets are promising therapeutic options when combined with traditional antidepressants. However, the mechanisms of action of these strategies are incompletely understood. Accumulating evidence suggests that physical exercise and specific dietary regimens can modulate both the immune system and gut microbiota composition. Here, we review the current information about the strategies to alleviate depression and their crosstalk with both inflammatory mechanisms and the gut microbiome. We further discuss the role of the microbiota-gut-brain axis as a possible mediator for the adjunctive therapies for depression through inflammatory mechanisms. Finally, we review existing and future adjunctive strategies to manipulate the gut microbiota with potential use for depression, including physical exercise, dietary interventions, prebiotics/probiotics, and fecal microbiota transplantation.