By smelling human breath, trained dogs can recognize the scent of reactions to trauma and help their owners by alerting them to early signs of distress.
- In the study, two dogs were able to detect stress-related volatile organic compounds in the breath of people with a history of trauma, with 90% accuracy.
- The performance of the dog, called Ivy, correlated with anxiety, while that of the other dog, Callie, correlated with shame.
- “Ivy was attuned to hormones of the sympathetic-adreno-medullary axis (like adrenaline) and Callie was attuned to hormones of the hypothalamic-pituitary-adrenergic axis (like cortisol).”
Post-traumatic stress disorder is a mental health disorder with a high prevalence among both military personnel and the general population. Assistance dogs for patients affected by this syndrome constitute a complementary and alternative intervention “requiring scientific validation”. In a new study, scientists from Dalhousie University (Canada) wanted to know if these animals could detect volatile organic compounds (i.e. molecules emitted by the body in secretions like sweat) linked to stress in the breath of people with a history of trauma.
Dogs can detect distinct endocrine stress markers
To carry out their work, the team recruited 26 adults, 54% of whom met the diagnostic criteria for post-traumatic stress disorder. Breath samples were taken during 40 experiments, specifically in a calm state and in a state of stress induced by exposure to trauma reminders. Next, participants had to fill out a questionnaire about their stress level and emotions. Second, the researchers presented the breath samples to two dogs, Callie and Ivy, who were trained to recognize the smell of stress.
According to the results, published in the journal Frontiers in Allergy, the dogs’ accuracy in distinguishing between a “stressed” and a “non-stressed” sample was 90%. In a second experiment, Ivy achieved 74% accuracy and Callie 81%. Further analysis of the animals’ olfactory performance in relation to volunteers’ reported emotional responses to exposure to trauma reminders suggested that the dogs could detect distinct endocrine stress markers.
Post-traumatic stress: their performance was correlated with anxiety and shame
Ivy’s performance correlated with anxiety, while Callie’s performance correlated with shame. “We assumed that Ivy was in tune with hormones of the sympathetic-adreno-medullary axis (like adrenaline) and that Callie was in tune with hormones of the hypothalamic-pituitary-adrenergic axis (like cortisol) This is important knowledge for training service dogs, as detecting early symptoms of post-traumatic stress requires sensitivity to hormones of the sympathetic-adreno-medullary axis. has explained Laura Kiirojawho led the research.
In future studies, the authors plan to perform experiments to confirm the involvement of the sympathetic-adreno-medullary axis. “Our study proves a concept that needs to be validated by work with larger samples. In addition to recruiting a larger number of participants, validation studies should collect samples from a larger number of events stressors to confirm the ability of dogs to reliably detect volatile organic stress compounds in human breath in different contexts.”