Effect of add-on yoga therapy on heart rate variability in patients with schizophrenia: An open-label pilot study

BACKGROUND Schizophrenia is associated with autonomic nervous system dysfunction and reduced heart rate variability (HRV). Antipsychotics, especially second-generation agents, may further impair cardiovascular autonomic regulation, raising the risk of cardiovascular disease and sudden cardiac death. Yoga, a structured mind-body intervention, has shown promise in improving autonomic function. OBJECTIVE To evaluate the effect of add-on yoga therapy on HRV and psychopathology in patients with schizophrenia. METHODS This open-label pilot study enrolled 45 participants: 15 patients in a Yoga Group (YG), 15 in a Control Group (CG), and 15 healthy controls (HC). The YG received a validated 10-day yoga intervention (60 min/day) added to standard pharmacotherapy; the CG continued treatment as usual. Outcomes included HRV parameters (SDRR, RMSSD, LF power, HF power, LF/HF ratio), SAPS, SANS, BPRS, and BMI. RESULTS At baseline, SDRR (F(2,42) = 16.52, p < 0.01) and RMSSD (F(2,42) = 6.72, p = 0.003) were markedly lower in both patient groups than HC. Post-intervention, the YG showed a significant reduction in LF/HF ratio (p = 0.039; Cohen's d = 0.60), indicating a shift toward parasympathetic predominance. Within-group improvements were significant for BPRS, SAPS, SANS, and BMI (all p < 0.01). Post-intervention SDRR and RMSSD remained significantly lower in the YG than HC (Hedges' g = 1.86 and 1.20), reflecting persistent autonomic deficits. CONCLUSION A 10-day structured yoga intervention may improve autonomic balance and reduce psychopathology in schizophrenia. Adequately powered randomised controlled trials with longer follow-up are needed to confirm these findings.