Dogs Can Detect PTSD Episodes By Smelling Humans' Breath: Study

Dogs might be able to detect an onset of a post-traumatic stress episode, according to a new study.

Post-traumatic Stress Disorder (PTSD) arises from being exposed to a catastrophic or traumatic event. Symptoms can include re-experiencing that catastrophic event, hyperarousal, avoiding any reminders, and cognitive or mood issues.

While dogs are currently trained to respond to behavioural and physical cues suggesting the study showed that at least some dogs can also detect these episodes via breath, according to Laura Kiiroja of Dalhousie University, Canada, first author of the study published in the journal Frontiers in Allergy.

"PTSD service dogs are already trained to assist people during episodes of distress," Kiiroja said.

For the study, the scientists recruited 26 humans as 'scent donors', 54 per cent of whom met the diagnostic requirements for PTSD. They 'donated' scents by attending sessions where they were reminded of their traumatic experiences while wearing different facemasks.

One facemask, worn by the participants under normal conditions, provided a calm breath sample, while another one, worn while recalling trauma, provided a target breath sample. The participants also responded to a questionnaire about their stress levels and their emotions.

The scientists also recruited 25 pet dogs to train in scent-detection. Only two -- Ivy and Callie -- were skilled and motivated enough to complete the study, they said.

These dogs were trained to recognise the target odour from the facemasks, and were found to be 90 per cent accurate in distinguishing between a stressed and a non-stressed facemask sample.

The scientists then presented the dogs with a series of samples - one at a time - to see if they could still accurately detect the chemicals the participants were releasing under stress and contributing to their 'scent profile'.

In this second experiment, Ivy achieved 74 per cent accuracy while Callie achieved 81 per cent accuracy.

"Both Ivy and Callie found this work inherently motivating," Kiiroja said. "Their limitless appetite for delicious treats was also an asset. In fact, it was much harder to convince them to take a break than to commence work. Callie in particular made sure there was no dilly-dallying." The researchers said that while there is some evidence that dogs may be capable of sensing bodily chemicals linked to a human's stress, no studies have investigated if dogs could learn to detect such chemicals linked to PTSD.

Dogs can help patients by alerting to and interrupting episodes when their companions are struggling with their symptoms, the researchers said.

If dogs could respond to their companions' stress markers on the breath, they could potentially interrupt PTSD episodes at an earlier stage, and make their interventions more effective, the team said.

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