Does HRV actually make a difference, or is it overhyped?

A 2017 meta-analysis found HRV biofeedback training — deliberately practicing slow, paced breathing to increase heart rate variability — produces a meaningful reduction in self-reported stress and anxiety, a mechanism-consistent finding supported by a separate meta-analysis showing voluntary slow breathing reliably increases HRV. Weighing the data: HRV looks an early-stage, lower-priority area for now — the evidence is only moderate (70/100), and its estimated impact (50/100) is on the lower end too.