Anxiety and autonomic regulation in major depressive disorder: An exploratory study

Spectral analysis of fluctuations in heart rate and blood pressure was employed to explore sympathetic and parasympathetic cardiovascular control mechanisms in relation to trait anxiety in major depressive disorder. Sixteen drug-free female depressed patients were divided into two groups: those who were high on trait anxiety (HTA, n = 9) and those who were normal or low on trait anxiety (LTA, n = 7). In patients and age-matched female controls (n = 10), heart rate (HR), blood pressure (BP; Finapres device) and respiration were recorded during a period of supine rest (10 min), orthostatic challenge (60 degrees head-up tilting, 8 min), and post-orthostatic supine rest (8 min). Power spectra were calculated over the last 4 min of these three situations for HR, systolic BP, as well as for respiration. Spectral density was assessed for three frequency bands: low (0.02-0.06 Hz), mid (0.07-0.14 Hz) and high (0.15-0.50 Hz). Patients did not differ from controls during supine rest. During orthostatic challenge, HTA patients showed significantly more HR increase and suppression of high-frequency fluctuations of HR (suggesting stronger vagal inhibition) in comparison with the controls; this effect was accompanied by a significant increase in respiratory frequency. Both patients groups did not show the normal increase in mid-frequency band fluctuations of BP during orthostatic challenge, indicating reduced sympathetic activation. Low-frequency fluctuations of HR, as well as respiratory frequency during post-orthostatic supine rest of the HTA patients were significantly increased versus controls. This exploratory study indicates that trait anxiety may be a relevant factor when evaluating parasympathetic and sympathetic dysbalances in the state of a major depressive disorder.