Associations Between Irritable Bowel Syndrome, Depression, Anxiety, and Suicidal Ideation: a Partial Least Squares Path Analysis.

Psychiatric comorbidities, especially depression, anxiety, and suicidal ideation, are highly prevalent among patients with Irritable Bowel Syndrome (IBS). Nevertheless, the ways in which psychological factors are associated with suicide risk in this population remain insufficiently understood. This study examined whether depression statistically mediates the association between anxiety and suicidal ideation among adults with IBS, within a gut–brain axis framework. A cross‑sectional study was conducted among 280 adults with IBS diagnosed according to the Rome IV criteria. Depression, anxiety, and suicidal ideation were assessed using validated Persian versions of the Beck Depression Inventory‑II (BDI‑II), Beck Anxiety Inventory (BAI), and Beck Scale for Suicide Ideation (BSS). Partial least squares structural equation modeling (PLS‑SEM) was used to estimate direct and indirect associations, with 5,000 bootstrap resamples. Model quality was evaluated using factor loadings, composite reliability, average variance extracted (AVE), heterotrait–monotrait ratio (HTMT), variance inflation factors (VIF), and standardized root mean square residual (SRMR). In additional sensitivity analyses, age, sex, IBS subtype, and previous psychiatric diagnosis were included as covariates predicting depression and suicidal ideation to assess the robustness of the main structural paths. Clinically significant depression, anxiety, and high suicide risk were observed in 41.1%, 35.7%, and 12.5% of participants, respectively. Higher anxiety scores were positively associated with higher depression scores (β = 0.43, p < 0.001), and higher depression scores were associated with higher suicidal ideation (β = 0.56, p < 0.001). Anxiety also showed a direct positive association with suicidal ideation (β = 0.18, p = 0.026), and the indirect association of anxiety with suicidal ideation via depression was statistically significant (β = 0.24, p = 0.008). The model explained 52% of the variance in suicidal ideation (R²=0.52), and measurement model criteria were fully met (CR = 0.89–0.94; AVE = 0.59–0.71; HTMT < 0.85). In sensitivity analyses adjusting for age, sex, IBS subtype, and previous psychiatric diagnosis, the direction and magnitude of the main paths and the indirect effect via depression remained largely unchanged. Findings suggest that depression may occupy a central, mediating role in the pattern of associations linking anxiety and suicidal ideation within the gut–brain–suicide network among IBS patients. Routine screening for depressive symptoms and suicidal ideation in gastrointestinal settings, together with integrated biopsychosocial management, may help identify patients at elevated risk, although causal relationships cannot be inferred from these cross‑sectional data.