Assessing response to stressful emotions: a controlled crossover study using pupillometry.

Background: Fear and horror induce autonomic protective responses, acting as "survival intelligence." Pupillometry is an innovative method that captures real-time autonomic nervous system reactions to stress.

Objective: To evaluate the feasibility of pupillometry to assess the acute response to a passive real-life stressor-viewing a truthful war scene.

Methods: Thirteen medical students (10 women) with an average age of 20.4 years were enrolled in a nonrandomized controlled crossover trial. Selected clips from two different audiovisual stimuli (M1: Saving Private Ryan as a fear and horror inducer and M2: Life Is Beautiful as a control) were watched for 15 minutes, separated by a washout period of 48-72 hours. The differences in pupillometry parameters between the exposure movie and the assessment time (T0 and T1 for M1 and T0 and T1 for M2) were evaluated using a Wilcoxon test. The Wilcoxon test was also used to assess the difference between M1 and M2 within each assessment time point (T0 and T1).

Results: A significant difference in response to acute fear and horror-induced stress was observed in pupillometry parameters {baseline [6.90 (5.95; 7.40) vs. 6.60 (5.55; 7.10), P = 0.030] and final pupil diameter [4.50 (3.90; 5.20) vs. 4.10 (3.50; 4.60), P = 0.012]} between M1 and M2 in T1, suggesting the acute increase in sympathetic parameters. Although not significant, there was also a difference in pupillometry parameters (final pupil diameter [P = 0.060], average constriction velocity [P = 0.059]) after watching M1 compared with T0.

Conclusion: Our proof-of-concept study suggests that pupillometry may be used to evaluate changes in the activity of the autonomic nervous system induced by an acute passive stress stimulus.