Stress-detecting dogs learn to sniff out PTSD

Dogs could soon sniff out an oncoming post-traumatic stress disorder (PTSD) flashback after a pair of pooches were trained to smell stress on survivors’ breath.

A pilot study has shown that our four-legged friends can be taught to recognise the scent of trauma reactions.

Scientists say the breakthrough will make PTSD assistance dogs more effective.

PTSD is a mental health condition that’s triggered by a terrifying event such as a car crash or terror attack, either experiencing it or witnessing it.

Symptoms may include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.

However, sniffing out PTSD is still tricky.

Dogs’ sensitive noses can detect the early warning signs of many potentially dangerous medical situations, such as an impending seizure.

But Ivy, a Golden Retriever, and Callie, a German Shepherd cross Belgian Malinois mix, were the only two of 25 dogs ‘skilled and motivated enough’ to complete the rigorous training process.

First author Laura Kiiroja, of Dalhousie University, Canada, said: ‘PTSD service dogs are already trained to assist people during episodes of distress.

‘However, dogs are currently trained to respond to behavioural and physical cues.

‘Our study showed that at least some dogs can also detect these episodes via breath.’

She said assistance dogs can help patients by alerting to and interrupting episodes when their companions are struggling with their symptoms.

If dogs could respond to stress markers on the breath, the research team say they could potentially interrupt episodes at an earlier stage – making their interventions more effective.

All humans have a ‘scent profile’ of volatile organic compounds (VOCs) – molecules emitted by the body in secretions such as sweat – influenced by our genetics, age, activities, and other variables.

There is some evidence that dogs may be capable of detecting VOCs linked to human stress.

However, no studies have previously investigated whether dogs could learn to detect VOCs associated with PTSD symptoms.

Ms Kiiroja said: ‘This is a multidisciplinary collaboration between Dr Sherry Stewart’s clinical psychology lab and Dr Simon Gadbois’ canine olfaction lab, both at Dalhousie University.

‘Neither lab could have done this work on their own. We brought together two distinct sets of expertise.’

The scientists recruited 26 people as scent donors. The participants were also taking part in a study about the reactions of people who have experienced trauma to reminders of that trauma – 54% met the diagnostic requirements for PTSD.

To donate scents, the participants attended sessions where they were reminded of their trauma experiences while wearing different facemasks.

One facemask provided a calm breath sample that acted as the control, while another, which was worn as the participants recalled their traumatic experience, provided a target breath sample.

The participants also completed a questionnaire about their stress levels and their emotions.

The research team recruited 25 pet dogs to train in scent-detection. Only two, Ivy and Callie, completed the study.

Ms Kiiroja, currently working on her PhD in biomedical scent-detection dogs, said: ‘Both Ivy and Callie found this work inherently motivating.

‘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.’

Ivy and Callie were trained to recognise the target odour from pieces of the facemasks.

They achieved 90% accuracy in discriminating between a stressed and a non-stressed sample, according to the study published by the journal Frontiers in Allergy.

The dogs were then presented with a series of samples, one at a time, to see if they could still accurately detect the stress VOCs.

In the second experiment, Ivy achieved 74% accuracy while Callie achieved 81%.

The team now plans to carry out further research.

Ms Kiiroja added: ‘With 40 sample sets, ours is a proof-of-concept study that needs to be validated by 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 VOCs in the breath of one human across different contexts.’