Dynamics in physiological acute stress response trajectories: uncovering latent variability

Background: Acute stressors trigger an immediate physiological response, involving multiple intricating pathways. These adaptive physiological responses include, among other processes, an increase in heart rate (HR) and a decrease in heart rate variability (HRV). Despite substantial efforts, linking individual variability in physiological acute stress response patterns with related psychological constructs such as anxiety and depression remains challenging. Notably, the majority of studies to date treated physiological stress responses as static entities, overlooking putative inter-individual variability in the dynamics at which physiological acute stress response trajectories unfold over-time. Methods: To address this gap, physiological responses (HR and HRV) were continuously recorded from 78 healthy adult female participants during an established 10-min-long laboratory acute stress induction manipulation. These physiological responses were separately quantified for three consecutive 3.3-min-long segments that together encompass the entire acute stress procedure, as well as for the 3.3-min-long segments immediately before and after stress. Results: At the whole group level stress was found to immediately increase HR, while HRV showed a delayed decrease with a post-stress overshoot effect. Latent class modeling revealed subgroups with unique physiological response trajectories, including a subset of participants that exhibited an atypical increase in HRV during stress. These individuals also exhibited elevated anxiety levels. Conclusions: Results underscore the complexity of physiological responses to acute stress and suggest that a dynamic approach could contribute to our understanding of the interplay between physiological stress responses and related psychological constructs. Further research is needed to replicate these findings and explore putative implications for stress-related mental health conditions.