RSA fluctuation in major depressive disorder.

Cardiac vagal control, as measured by indices of respiratory sinus arrhythmia (RSA), has been investigated as a marker of impaired self-regulation in mental disorders, including depression. Past work in depressed samples has focused on deficits in resting RSA levels, with mixed results. This study tested the hypothesis that depression involves abnormal RSA fluctuation. RSA was measured in depressed and healthy control participants during rest and during two reactivity tasks, each followed by a recovery period. Relative to controls, depressed persons exhibited lower resting RSA levels as well as less RSA fluctuation, primarily evidenced by a lack of task-related vagal suppression. Group differences in RSA fluctuation were not accounted for by differences in physical health or respiration, whereas group differences in resting RSA level did not survive covariate analyses. Depression may involve multiple deficits in cardiac vagal control.