Effect of Yoga-based Intervention on Stress and Autonomic Balance in Substance Abuse Recovery: A Psychophysiological Study

Background: Individuals with substance use disorders (SUD) commonly exhibit elevated psychological stress, autonomic dysregulation, and altered biochemical stress markers, which adversely affect rehabilitation outcomes.Mind-body interventions, such as yoga, may support recovery by modulating psychophysiological stress pathways.This study examined the effects of a structured yoga-based intervention on psychological stress, autonomic function, and biochemical stress markers among inpatients undergoing substance abuse rehabilitation in Kerala, India.Materials and methods: A quasi-experimental, pre-post control group design was employed due to practical constraints within the rehabilitation setting.Sixty male inpatients aged 18-50 years were allocated to either an experimental group (n = 30) receiving yoga in addition to standard rehabilitation care, or a control group (n = 30) receiving standard rehabilitation care alone.The yoga intervention was conducted for 12 weeks, six sessions per week, each lasting 60 minutes, and included asanas, pranayama, and meditation.The control group participated in routine rehabilitation activities, including counseling, group sessions, recreational activities, and medical supervision.Psychological stress was assessed using the depression anxiety stress scales-21 (DASS-21) stress subscale and the perceived stress scale (PSS-10).Autonomic function was evaluated through heart rate variability (HRV) indices [standard deviation of normal-to-normal intervals (SDNN), root mean square of successive Differences (RMSSD), and the low frequency (LF)/high frequency (HF) ratio].Serum cortisol and C-reactive protein (CRP) were measured as biochemical stress markers.Data were analyzed using paired and independent t-tests, Pearson's correlation, and Cohen's d.Baseline-adjusted analysis of covariance (ANCOVA) was applied with pre-intervention scores as covariates to control for initial group differences.Statistical significance was set at p < 0.05. Results:The yoga group demonstrated significant reductions in psychological stress scores and significant improvements in HRV indices, alongside decreases in serum cortisol and CRP levels (p < 0.01).The control group showed no significant changes.Baseline-adjusted ANCOVA confirmed that post-intervention group differences remained significant after controlling for baseline scores.Reductions in psychological stress were positively correlated with improvements in HRV and decreases in biochemical stress markers, indicating coordinated psychophysiological regulation. Conclusion:A 12-week yoga-based intervention adjunctive to standard rehabilitation care was associated with significant improvements in psychological stress, autonomic regulation, and biochemical stress markers in individuals with SUD.While causal inference is limited by the quasi-experimental design, these findings support the potential role of yoga as a complementary intervention in substance abuse rehabilitation.