Atypical development of resting respiratory sinus arrhythmia in children at high risk for depression.

Compromised respiratory sinus arrhythmia (RSA, i.e., low cardiac vagal control) frequently characterizes clinically depressed adults and also has been detected in infants of depressed mothers; however, its existence has not been established in older at-risk offspring. We investigated developmental patterns of RSA in a sample of 163 5- to 14-year-old children, who were either at high risk for depression (due to having a parent with a childhood-onset mood disorder) or low-risk for depression. We hypothesized that high-risk children have lower resting RSA than do low-risk children, which could reflect atypical developmental trajectories. Children's RSA was assessed during resting baseline periods on multiple occasions, typically 1-year apart. Linear growth modeling indicated a group by age interaction. Low-risk children (but not the high-risk children) exhibited a significantly increasing trajectory in resting RSA with age. Mood disorders in offspring did not account for the Group X Age interaction effect. Our study provides new evidence that children at high risk for depression have an atypical developmental trajectory of RSA across late childhood.