Autonomic Arousal and Perseverative Cognition Are Associated with Depression and Suicidal Ideation: A Moderated-Mediation Model

Perseverative cognition—frequently expressed through obsessive–compulsive symptoms—is a recognized trans-diagnostic risk factor for psychopathology, with documented links to depression and suicidal ideation. While the literature suggests that altered autonomic arousal in depression may relate to suicidal risk, the conditional architecture linking these variables remains insufficiently explored. This study examined whether suicidal ideation mediates the association between depression and autonomic arousal and whether obsessive–compulsive symptoms moderate the initial pathways within this mechanism. A sample of 120 university students (61.8% female; Mage = 28.6, SDage = 10.71) completed the Symptom Checklist-90-Revised (SCL-90-R), from which the depression, obsessive–compulsive, and suicidal ideation scores were derived; notably, the suicidal ideation score was calculated from specific items (15 and 59) embedded within the depression subscale. All participants underwent a psychophysiological evaluation to record baseline Electrodermal Activity (EDA) as an index of tonic autonomic arousal. Results indicated that depression significantly predicted suicidal ideation (B = 0.05, SE = 0.006, p < 0.001, 95% CI [0.03, 0.06]), which, in turn, was a significant predictor of autonomic arousal (B = 0.17, SE = 0.08, p = 0.03, 95% CI [0.02, 0.33]). Additionally, the mediation analysis revealed that depression showed an indirect statistical association with autonomic arousal through suicidal ideation (Bootstrapped 95% CI [0.01, 0.12]). Concurrently, obsessive–compulsive symptoms significantly moderated the psychological link between depression and suicidal ideation (B = 0.20, SE = 0.04, p < 0.001, 95% CI [0.04, 0.37]), accounting for 38.40% of the variance (F (4, 115) = 22.17, p < 0.001). Sensitivity analyses, conducted by re-calculating the models after excluding items 15 and 59 from the depression score, confirmed the robustness of these findings against potential psychometric overlap. However, the formal Index of Moderated Mediation was not statistically significant (0.0000 (95% Boot CI [−0.0001, 0.0001]), explicitly demonstrating that this psychological moderation did not translate into a significant conditional indirect effect on peripheral autonomic arousal. These findings suggest that while obsessive cognitive patterns significantly intensify the psychological burden of depression into thoughts of death, their concurrent association with peripheral physiological parameters remains strictly exploratory in non-clinical cohorts, underscoring a nuanced underscoring a nuanced ‘blocking’ effect—both emotional and behavioral—where obsessive rigidity functions as a mechanism of paralysis that, while generating profound subjective distress, fails to translate into a corresponding reactive physiological response of the autonomic nervous system.