Felix Menne, Hali Lindsay, Johannes Tröger, Silke Paulmann, Alexandra König, Nadine Steinbach, Andreas Reif, Michael M. Plichta, Maren Schmidt-Kassow
Acta Neuropsyhiatrica. 2025.
Abstract:
Objective: Cortisol is a well-established biomarker of stress, assessed through salivary or
blood samples, which are intrusive and time-consuming. Speech, influenced by physiological
stress responses, offers a promising non-invasive, real-time alternative for stress detection.
This study examined relationships between speech features, state anger, and salivary cortisol
using a validated stress-induction paradigm. Methods: Participants (N = 82) were assigned to
cold (n = 43) or warm water (n = 39) groups. Saliva samples and speech recordings were
collected before and 20 minutes after the Socially Evaluated Cold Pressor Test (SECPT),
alongside State–Trait Anger Expression Inventory (STAXI) ratings. Acoustic features from
frequency, energy, spectral, and temporal domains were analysed. Statistical analyses
included Wilcoxon tests, correlations, linear mixed models (LMMs), and machine learning
(ML) models, adjusting for covariates. Results: Post-intervention, the cold group showed
significantly higher cortisol and state anger. Stress-related speech changes occurred across
domains. Alpha ratio decreased and MFCC3 increased post-stress in the cold group,
associated with cortisol and robust to sex and baseline levels. Cortisol–speech correlations
were significant in the cold group, including sex-specific patterns. LMMs indicated baseline
cortisol influenced feature changes, differing by sex. ML models modestly predicted SECPT
group membership (AUC = 0.55) and showed moderate accuracy estimating cortisol and
STAXI scores, with mean absolute errors corresponding to ~ 24–38% and ~16–28% of
observed ranges, respectively. Conclusion: This study demonstrates the potential of speech
features as objective stress markers, revealing associations with cortisol and state anger.
Speech analysis may offer a valuable, non-invasive tool for assessing stress responses, with
notable sex differences in vocal biomarkers.