Carney believes that the large amounts of stress hormones produced by depressed patients may affect the body's autonomic nervous system, which controls heart rate. That could explain the link. The researchers will follow the study patients for at least 18 months to learn whether the depressed and nondepressed patients have different mortality rates. They also will determine whether treatment for depression improved heart-rate variability. A small study has suggested a modest improvement, but Carney would like to follow those patients for a longer time.
Patients do feel better after therapy.
What we don't know yet is whether their improved mood translates into higher heart-rate variability and reduced mortality. We suspect it might, but we still need to investigate that.