GSTM1 and sexually transmitted disease: In the present study, HRV‐BF increased vagal tone (Figure 5), partially restored Hb‐related network connectivity (Figure 4, right panel and Figure 6), and alleviated depressive symptoms in StD participants, supporting the role of the Hb as a regulatory node of the brain–heart axis and providing neurofunctional evidence for HRV‐BF intervention.