Dogs can detect stress-related compounds in the breath of people experiencing early signs of trauma, including those with posttraumatic stress disorder (PTSD), a new proof-of-concept study suggested.
The research provides evidence that some service dogs with PTSD can be trained to detect episodes of pending distress through a person’s breath and perhaps prompt the individual to use coping skills to manage the episode.
“Ours is the first study to demonstrate that at least some dogs can detect putative stress-related volatile organic compounds in human breath that are associated with PTSD symptoms,” study author Laura Kiiroja, PhD candidate, department of psychology and neuroscience, faculty of science, Dalhousie University, Halifax, Nova Scotia, Canada, told this news organization.
The study was published online on March 28, 2024, in Frontiers of Allergy.
Heightened Sense of Smell
The lifetime prevalence of PTSD is about 8% in the general population, but data show it can reach 23% in veterans. In addition, many more trauma-exposed individuals experience subthreshold symptoms.
Research is investigating the application of dogs’ sense of smell — which is up to 100,000 times more sensitive than humans’ — to detect cancers, viruses, parasites, hypoglycemia, and seizures in humans.
The new study included 26 mostly civilian “donors” (mean age, 31 years; 18 females) who had experienced various types of trauma but had no severe mental illness. More than 50% met the criteria for PTSD.
Participants were recruited from a study examining neurocognitive mechanisms underlying the potential links between trauma and cannabis use. However, participants in the dog study abstained from using cannabis for at least 12 hours prior to the study experiments.
Breath Donors
Breath samples were collected via disposable medical-grade face masks at baseline and during ensuing experiments. In total, 40 breath sample sets were collected.
Two female companion dogs — Ivy, a red golden retriever, and Callie, a German shepherd/Belgian Malinois mix — were trained to identify target odors from the samples.
The animals were tested to determine whether they were able to discriminate between breath samples collected from these same “breath donors” during a relatively relaxed state and during induced stress testing which is known as the alternative forced choice discrimination test.
The dogs’ ability to discern trauma cues from breath samples of various individuals was tested by presenting one sample (baseline or trauma cue) at a time. The researchers used signal detection theory to evaluate the sensitivity and specificity of dogs in detecting human stress VOCs.
Investigators found the dogs had about a 90% accuracy rate across all sample sets in the discrimination experiment and 74% and 81% accuracy for Ivy and Callie, respectively, in the detection experiment.
“Our study contributed to the evidence showing that not only are dogs able to detect some physical health conditions in humans but also that some mental health conditions alter the released VOCs in a way that is detectable by dogs,” Ms. Kiiroja said.