To investigate the role of the habenula (Hb)‐centered brain network in regulating the cardiac autonomic nervous system (ANS) in subthreshold depression (StD), and to explore the brain–heart axis mechanisms underlying the antidepressant effects of heart rate variability biofeedback (HRV‐BF) as a non‐pharmacological intervention. This evidence concerns the gene GSTM1 and depressive disorder.