Heart rate variability reactivity moderates the relationship between behavioral disinhibition and suicide attempts in mood disorders

BACKGROUND Distinguishing suicide attempters from those with only ideation remains a major clinical challenge. This study investigated whether heart rate variability (HRV) reactivity, a marker of autonomic regulation, moderates the relationship between behavioral disinhibition and suicide attempts. METHODS We conducted a cross-sectional study of 61 inpatients with major depressive episodes, categorized into a Suicide Attempt group (SA, n = 23) and a Suicidal Ideation group (SI, n = 38). HRV was recorded during baseline and Go/No-Go task performance as a stress condition. We calculated HRV reactivity as the change in log-transformed high-frequency (HF) power from baseline to task. Logistic regression and interaction analyses were used to predict attempt status while adjusting for age, sex, and smoking. RESULTS The SA group was significantly younger and had more lifetime attempts. Groups did not differ in depression, self-reported impulsivity, or aggression (all p > 0.05). Unadjusted analyses showed the SA group had fewer omission errors (Median: 4.0 vs. 9.0, p = 0.014) and higher resting HRV-HF Power (181.0 vs. 63.5 ms2, p = 0.033) compared to the SI group. However, these differences were attributable to younger age and became non-significant after adjustment. In exploratory interaction analyses, a significant effect emerged between Go/No-Go commission errors and HRV-HF reactivity (β = 0.12, p = 0.022). High commission errors were associated with suicide attempts only when coupled with blunted HRV reactivity. CONCLUSION Recent suicide attempt was associated with the coexistence of motor disinhibition and impaired HRV-HF reactivity. These exploratory findings highlight the importance of stress-related physiological reactivity over resting measures for risk stratification, providing preliminary proof-of-concept for differentiating high-risk subgroups.