Emotional body odors alter autonomic nervous activity during mindfulness training in social anxiety

Chemosignals found in human body odors (BOs) convey information about a person's emotional state and elicit observable responses in others. While mindfulness typically enhances parasympathetic tone and reduces anxiety, little is known about how BOs modulate these effects. This study investigated how emotional and non-emotional human BOs influence autonomic nervous system activity - heart rate variability (HRV) and electrodermal activity (EDA) - during mindfulness practice in individuals with social anxiety. The role of baseline HRV as a predictor of intervention outcome was explored. Ninety-eight women with social anxiety received two mindfulness sessions over two consecutive days, while allocated to one of four conditions: fear BO, happiness BO, neutral BO, clean air. Due to technical issues, final samples were reduced (n = 69-85 per analysis). Individuals in the fear and happiness BOs conditions, but not those in the neutral BO and clean air conditions, showed HRV reduction during the mindfulness. EDA decreased in all conditions on day 1, but on day 2, only the clean air and neutral BO groups maintained this reduction. Baseline HRV predicted the magnitude of anxiety reduction in the fear BO group; participants with higher initial HRV exhibited greater anxiety reduction. No associations were found for other odor conditions. These results suggest that emotional BOs, particularly fear BO, may enhance mindfulness efficacy by creating a socially salient and ecologically valid context. For socially anxious individuals, practicing mindfulness under a subtle social-emotional challenge may train adaptive regulation. Baseline HRV emerges as a biomarker of such regulatory flexibility and intervention responsiveness.