Some dogs can detect oncoming PTSD hyperarousal symptoms from sniffing human breath. The corresponding study was published in Frontiers in Allergy.
Around 6% of people in the US have PTSD at some point in their life. Psychiatric service dogs are a complementary or alternative treatment option for the condition. Their tasks include alerting to early signs of hyperarousal symptoms and interrupting or diffusing these episodes. PTSD service dogs are linked to better quality of life and improved family and social functioning and integration.
Currently, PTSD service dogs are trained to respond to physical signs of PTSD hyperarousal symptoms such as fidgeting and fist-clenching. In the current study, researchers investigated whether dogs can also detect early onset of these episodes by smelling the breath of people with trauma histories when reminded of their trauma.
For the study, researchers recruited 26 human participants, around half of whom met the diagnostic requirements for PTSD. The researchers collected scent samples from the participants during experimental sessions in which they wore facemasks while in a calm state and being reminded of previous trauma. Participants also filled in a questionnaire about their stress levels and emotions.
The researchers further recruited 25 pet dogs of different breeds to train in scent detection. Only two dogs- a spayed female Red Golden Retreiver called Ivy, and a spayed female mix of German Shepherd and Belgian Malinois named Callie- were sufficiently skilled and motivated to complete the study. To begin, both dogs were trained to recognize the target odour from pieces of facemasks. Ultimately, they achieved 90% accuracy in discriminating between stressed and non-stressed samples.
Next, they were presented with a series of samples one at a time. In this experiment, Ivy detected breath from participants recalling their trauma with 74% accuracy, whereas Callie did so with 81% accuracy. When comparing the dogs' successful identifications with human participants’ self-reported emotions, they found that Ivy’s detections correlated with anxiety, while Callie’s correlated with shame.
“Although both dogs performed at very high accuracy, they seemed to have a slightly different idea of what they considered a ‘stressed’ breath sample,” said first author of the study, Laura Kiiroja, of Dalhousie University, in a press release.
“We speculated that Ivy was attuned to sympathetic-adreno-medullar axis hormones (like adrenaline) and Callie was oriented to the hypothalamo-pituitary-adrenal axis hormones (like cortisol). This is important knowledge for training service dogs, as alerting to early-onset PTSD symptoms requires sensitivity to sympathetic-adreno-medullar axis hormones.”
Kiiroja noted that this is a proof-of-concept study, and that it needs to be validated by further studies with larger sample sizes.
“In addition to enrolling more participants, validation studies should collect samples from a higher number of stressful events to confirm dogs’ ability to reliably detect stress volatile organic compounds in the breath of one human across different contexts,” concluded Kiiroja.
Sources: Neuroscience News, Frontiers in Allergy
