Probiotic Use and Self-Reported Psychological, Cognitive, and Gastrointestinal Outcomes in a Community Sample: A...

Research on probiotics and health outcomes has produced mixed findings. While the gut-brain axis provides a theoretical framework for probiotics to influence psychological and cognitive health, evidence remains inconsistent, particularly in community samples. This study examined associations between probiotic use and psychological, cognitive, and gastrointestinal outcomes, with particular attention to delivery method (supplement vs. fermented food).

One hundred and fifty adults (M = 25.82, SD = 10.99) completed validated measures of depressive and anxiety symptoms, stress resilience, gastrointestinal complaints, cognitive lapses, hazardous drinking, and disordered eating. Group differences were examined using Kruskal-Wallis tests (unadjusted) and two covariate-adjusted ANCOVA models (Model 1: age, gender, and physical activity; Model 2: additionally adjusting for prebiotic use and dietary adherence).

In unadjusted analyses, probiotic supplement users reported lower depressive and anxiety symptoms, fewer gastrointestinal complaints, and reduced cognitive lapses than non-probiotic users. After adjustment, gastrointestinal symptoms remained significantly associated with probiotic use across both models (p = 0.034, Model 1; p = 0.017, Model 2). Anxiety symptoms and cognitive lapses were significantly associated with probiotic use in Model 1 (p = 0.026 and p = 0.018, respectively) but attenuated to non-significance in the fully adjusted model. Stress resilience was non-significant in Model 1 but reached significance in Model 2 (p = 0.035). However, none of these associations survived Bonferroni correction for multiple comparisons across the five primary outcomes (α = 0.01). Fermented food users did not differ from other groups on any outcomes.

In this community sample, unadjusted analyses suggested probiotic supplement use was associated with lower depressive symptoms, anxiety symptoms, gastrointestinal symptoms, and cognitive lapses. After adjustment, gastrointestinal symptoms showed the most consistent association, while anxiety symptoms, cognitive lapses, and stress resilience showed inconsistent, model-dependent associations. No associations were robust to correction, and all findings should be interpreted as preliminary. Longitudinal and experimental research with larger samples is needed to establish causality and clarify the conditions under which probiotic use may confer health benefits.