An exploratory analysis on the association between suicidal ideation and the microbiome in patients with or without major depressive disorder

Background: Scarce research has investigated associations between suicidal ideation and the gut microbiota. We aimed to explore variations in the gut microbiome associated with suicidal ideation and major depressive disorder (MDD).

Method: A case-control study compared abundances of fecal microbiota and biomarkers of gut permeability among patients with MDD, with or without suicidal ideation, and healthy volunteers without depression. Information on demographic variables and assessments of suicidal ideation (Beck Suicidal Ideation Scale), depression (Hamilton Depression Scale, Patient Health Questionnaire, Hospital Anxiety and Depression Scale- Depression), as well as anxiety (Hospital Anxiety and Depression Scale- Anxiety), were obtained. Univariate and multivariate regression model was performed to explore the possible predictors of suicidal ideation.

Results: Among the 140 participants, significant differences in Beta diversity were found between MDD patients with (n = 43) or without suicidal ideation (n = 34), and healthy volunteers (n = 42) (all p < 0.001). The strain of g-Phascolarctobacterium was found to have significant positive associations with scores of BSSI and BSSI Part 1 (suicidal ideation), particularly in MDD patients with suicidal ideation, after controlling for demographic and mood covariates. Mediation analyses revealed that g-Phascolarctobacterium may be a partial mediator between depression and suicidal ideation; however, it is also possible that the association between g-Phascolarctobacterium and suicidal ideation was partially mediated by the level of depression.

Conclusion: We found different compositions, diversities, and possible mediating of the gut microbiome associated with suicidal ideations. Potential mechanisms need further investigation to establish whether this reflects a biological process that might be the focus for intervention development.

Synopsis: Our objective was to investigate whether the diversities and abundances of the gut microbiome varied in people with or without suicidal ideation and with or without MDD after considering possible demographic and mood confounders.