Resting vagal tone is negatively associated with suicide ideation

The present study aimed at investigating whether resting vagally mediated heart rate variability (HRV) as a trait-like biomarker of cognitive inhibitory control capacity is related to suicide ideation in a sample without suicide attempt history.

Thirty-seven healthy students participated voluntarily (18 to 34 years, M=24.5, SD=4.1; 73.0% female). Time and frequency measures of HRV were derived from an electrocardiogram that was recorded using Einthoven's Triangle lead II. Participants filled in the Rasch-based Depression Screening and four questions concerning lifetime suicide ideation (SI). Bivariate Pearson's and partial (controlling for depression severity) correlation coefficients were calculated between SI and measures of vagally mediated HRV.

A significant correlation between the ln10-transformed high-frequency band of resting vagally mediated HRV and SI was found (r=-.33, p<.05). Correlations did not change substantially when controlling for depression. Mean heart rate as a time domain measure also significantly correlated with SI while controlling for depression (r=.36, p<.05). A trend correlation between SI and Root Mean Square of Successive Differences between interbeat intervals emerged.

SI was assessed with a composite score of four items measuring SI. Future studies should consider using more comprehensive assessment instruments.

The relation between resting vagally mediated HRV and suicide ideation may be interpreted as indicating that reduced inhibitory cognitive control capacity may be a risk factor for suicidality. It may act already early in the suicidal process, before suicidal behavior develops and should be further investigated as potentially clinically important physiological predictor of suicidality.