The relationship between pre-treatment heart rate variability and response to low-frequency accelerated repetitive transcranial magnetic stimulation in major depression

•There are no validated and scalable biomarkers for response prediction in MDD.•Heart rate variability (HRV) has shown promise in some antidepressant studies.•We tested the role of HRV for outcome prediction to accelerated 1 Hz rTMS in MDD.•A linear mixed effects model did not show association between HRV and outcomes.•Other approaches using cardiac biomarkers might prove useful.