Dogs can discriminate between human baseline and psychological stress condition odours.
Level 4 - case-series / case-control
Laboratory diagnostic/discrimination study using biological samples from 36 participants tested on 4 canine subjects
PubMed 36170254 · doi:10.1371/journal.pone.0274143
What was done
Combined breath and sweat samples were collected from 36 human participants at baseline and immediately following an acute psychological stressor (a mental arithmetic task). Stress was confirmed using self-report and physiological monitoring via a Biopac MP150 system. In a double-blind, two-phase, three-alternative forced-choice setup, four trained dogs evaluated the samples across 36 sessions (16, 11, 7, and 2 sessions per dog). Each session included 10 training trials (stress sample versus two blanks) and 20 discrimination trials (stress sample, matching baseline sample, and one blank) to measure whether dogs correctly alerted to the stress sample.
What was found
Across 720 discrimination trials in Phase Two, dogs alerted to the correct stress sample with individual accuracies ranging from 90.00% to 96.88% and a pooled accuracy of 93.75%. A binomial test against a 0.33 chance probability confirmed performance was significantly above chance (p < 0.001).
Why it matters
This study provides evidence that acute psychological stress alters human volatile organic compounds in breath and sweat sufficiently for canine olfactory detection. These findings offer an empirical physiological basis for the capability of psychiatric and post-traumatic stress disorder service dogs.
Limits
The study tested only four dogs, with highly unequal session allocation across animals (one dog completed only two sessions). The acute laboratory arithmetic stressor may not replicate real-world psychological distress, and the specific volatile organic compounds driving the olfactory discrimination were not chemically characterized.
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