Certain gut bacteria, including Bifidobacterium and Actinobacteria, were associated with a reduced risk of specific depressive symptoms, such as anhedonia and depressed mood, with body mass index acting as a potential mediator, according to a recent study.

The Mendelian randomization study examined causal relationships between gut microbiota (GM), body mass index (BMI), and specific depressive symptoms, exploring potential links between GM and depression. Researchers used genome-wide association study data to analyze the effects of GM on depressive symptoms and assessed BMI as a mediating factor.

Key findings showed that the Bifidobacterium genus (β=–0.03; 95% confidence interval [CI], –0.05 to –0.02; p<0.001) and the Actinobacteria phylum (β=–0.04; 95% CI, –0.06 to –0.02; p<0.001) exerted protective effects on anhedonia and depressed mood. Actinobacteria was also linked to a reduced risk of appetite changes (β=–0.04; 95% CI, –0.06 to –0.01; p=0.005), while Family XI was associated with an increased risk of appetite changes (β=0.03; 95% CI, 0.01 to 0.04; p<0.001). Additionally, Actinobacteria and the Bifidobacteriaceae family were associated with lower risks of suicidality (β=–0.01; 95% CI, –0.02 to –0.01; p=0.001). BMI mediated the effect of GM on depressive symptoms, with mediation proportions of 14.14% for Bifidobacterium and 13.10% for Actinobacteria in anhedonia, and 34.42% for Actinobacteria in appetite changes.

These findings, published in General Psychiatry, indicated that specific gut bacteria, particularly Bifidobacterium and Actinobacteria, may have a role in specific depressive symptoms, especially among patients with obesity. Although the study highlighted BMI as a mediating factor, further clinical trials were suggested to explore whether probiotics targeting these bacterial groups could influence depressive symptoms and metabolic disorders.

Full disclosures are available in the published study.