Severity of Depressive Symptoms by Perceived Stress and Gut Microbiota Composition: A Sex-Stratified Bayesian Approach in a Non-Clinical Sample.

Women reported higher perceived stress scores than men, but no sex differences were found in depressive symptom scores.

• Sample consisted of 398 healthy adults, 241 women and 157 men.
• Participants completed the Perceived Stress Scale (PSS) and the Center for Epidemiologic Studies Depression Scale (CES-D).
• Women had significantly higher PSS scores than men.
• No statistically significant differences were found between sexes on CES-D scores.

Men and women in this non-clinical sample were characterised by similar gut microbiota composition and diversity.

• Participants provided stool samples for gut microbiota analysis.
• No significant sex differences were detected in gut microbiota diversity measures.
• No significant sex differences were detected in gut microbiota compositional features.

Perceived stress predicted depressive symptoms in both men and women.

• Bayesian analyses were used to examine the relationship between perceived stress (PSS) and depressive symptoms (CES-D).
• The predictive relationship between PSS and CES-D was observed across both sexes.
• This finding held in a non-clinical, healthy adult sample.

In women, the genus Eubacterium moderated the relationship between perceived stress and depressive symptoms.

• Higher perceived stress combined with lower Eubacterium abundance predicted more severe depressive symptoms in women.
• This moderation effect was identified using Bayesian analyses.
• The moderation by Eubacterium was specific to women and was not observed in men.
• No gut bacterial moderators of the stress-depression relationship were found in men.

No moderation of the stress-depression relationship by gut bacteria was found in men.

• Bayesian analyses were conducted separately for men and women (sex-stratified approach).
• While perceived stress predicted depressive symptoms in men, no gut microbiota genus was identified as a moderator in this sex.
• The absence of bacterial moderation in men contrasts with the significant Eubacterium moderation found in women.

The genus Eubacterium is suggested as a promising microbial biomarker associated with depressive symptoms, particularly in women under higher stress levels.

• The finding points to the need for sex-specific investigations of stress and gut microbiota interactions.
• Eubacterium's role as a potential biomarker is framed within the context of the microbiota-gut-brain axis.
• The authors note this finding is from a non-clinical, healthy adult sample, warranting further investigation.