The gut-brain axis: Investigating the effects of diet, physical activity, and prior adversity on anxiety via autonomic nervous system

Abstract

Previous literature has highlighted a bidirectional relationship between the gut and brain called the gut-brain axis (de Punder & Pruimboom, 2015; Hill et al., 2008; Leistner & Menke, 2020). The current study aimed to investigate directional relations between different stressors (e.g. poor diet, vigorous activity, and prior adversity) and anxiety and how interactions with gut issues and autonomic dysfunction may impact these relationships. Based on previous literature, we examined (a) physical activity and diet as moderators of stress and anxiety as well as stress and GI symptoms, (b) GI symptoms as a mediator between various predictors (i.e., diet, stress, physical activity, prior adversity) and anxiety, and (c) GI symptoms and perceived stress as serial mediators for various stressors to anxiety. We also explored whether GI symptoms and autonomic reactivity serially mediate the relationship between stress and anxiety. We recruited our sample from university students (n = 177) and a Jacksonville, Fl community participant pool (n = 32) who answered survey questions regarding demographics, diet quality, physical activity, prior adversities, stress, autonomic reactivity, and anxiety. Key findings included: (a) vigorous activity was a significant moderator of the relationship between stress and GI symptoms; (b) GI symptoms significantly mediated the relationship between stress and anxiety as well as prior adversity and anxiety; (c) stress and GI symptoms were significant serial mediators of the relationship between diet quality and anxiety as well as prior adversity and anxiety; and (d) GI symptoms and autonomic reactivity were significant serial mediators of the relationship between stress and anxiety. Our findings suggest that factors such as diet and physical activity levels should be considered when examining gut-brain relations specific to stress, anxiety, and GI symptoms. Future research should investigate directionality of these relationships more clearly through longitudinal study designs, especially given the bidirectional nature of the gut-brain axis