Associations between heart rate variability, peripheral inflammatory markers and major depressive disorder

Background: Measures for the irregularity of the heartbeat, for example respiratory sinus arrhythmia, have been implicated as a measure for restorative functions of the vegetative nervous system. Methods: In the current observational study, we investigated 265 subjects, 70 of whom had a lifetime history of major depression, with a plethysmographic heartbeat monitor, blood sampling, as well as a range of psychiatric questionnaires. Results: Subjects with a history of MDE had significantly reduced respiratory sinus arrhythmia (RSA) as compared to never-depressed controls; in the whole sample, higher RSA went with lower anxiety/fear variables, especially in subscores related to cardiac symptoms as well as being afraid of dying. A reduced RSA was also associated with an increased concentration of cytokines (TNFa, IL1a, IL6, IFNg) and thyroid-stimulating hormone in the serum, pointing to a possible triangular relationship between immune system, vegetative nervous system, and emotional dysregulation. Limitations: We used a plethysmographic device for the measurement of heartbeat instead of an electrocardiogram, and had a single time point only. Conclusions: This data corroborate the idea that a disequilibrium of the vegetative nervous, especially if accompanied by a dysregulation system in immune function, can increase the risk for depression. Conversely, vagal stimulation and anti-inflammatory treatments may support the treatment with antidepressants.

Automated summary

Subjects with a history of major depressive episode (MDE) showed significantly reduced respiratory sinus arrhythmia (RSA) compared to those who never experienced depression. Higher RSA was associated with lower anxiety and fear levels, particularly in relation to cardiac symptoms and the fear of dying. Lower RSA was also linked to elevated levels of cytokines and thyroid-stimulating hormone in the serum, suggesting a potential connection between the immune system, vegetative nervous system, and emotional dysregulation.