Dogs have been trained to detect stress in people with PTSD by smell

Scientists from Canada have shown in an experiment that the sensitive noses of assistance dogs can "smell" signs of stress in people with post-traumatic stress disorder in the odor of their breath.

Olfaction is dogs' primary and most developed sense organ. Our four-legged friends' ability to detect odors is 10,000 to 100,000 times better than the average human. Researchers are studying the possibilities of using the keen sense of smell of dogs for biomedical purposes. For example, earlier they conducted experiments on detection by dogs of different human diseases, including cancer, viral and parasitic diseases.

Dogs are also able to sense the approach of life-threatening conditions. By detecting changes in odor, a trained animal warns its owner in advance of an epileptic attack or hypoglycemia (a drop in blood glucose levels).

Canadian experts in psychology and neuroscience from Dalhousie University suggested that in a similar way dogs can help sufferers of post-traumatic stress disorder (PTSD). The condition develops in survivors of a traumatic event - shock, extreme fright or danger - about 25 to 35 percent of the time. It is also common among those who have been involved in warfare. In the general population, PTSD is thought to occur in 7 to 10 percent of people.

One frequent symptom of PTSD is recurrent reliving of traumatic events, or flashbacks, which can be accompanied by falling into a stupor or panic attacks. Scientists believe dogs could interrupt such attacks, or even warn of them, by responding to stress markers in a person's breathing.

To test how realistic this is, the researchers organized a series of experiments. Their results were published in the journal Frontiers in Allergy.

Out of 25 potential candidate dogs, they managed to select only two suitable dogs. Sufficiently prepared and motivated to pass the experiment to the end, were a golden retriever Ivy and a mix of German Shepherd and Belgian Malinois named Kelly (both are females aged five to six years and three to four years at the time of the experiments).

On the human side, the odor donors were 26 participants in another study that examined the neurocognitive mechanisms responsible for the link between psychological trauma and cannabis use. Among the volunteers, 14 people, about 54 percent, met the diagnostic requirements for PTSD.

Odor samples for the experiments were obtained using face masks. Some, control masks, were donned and worn by donors in a calm state, while others, which became the target samples, were worn by volunteers during sessions where they were reminded of their trauma experiences. Participants also filled out questionnaires about their stress levels and their emotions.

Giving the dogs two pieces of face masks to sniff each, the animals were first trained to distinguish the target odor from the control odor and to point to the first with an agreed signal. At this stage, the dogs showed a 90 percent accuracy in identifying the stressed samples.

In the second series of experiments, the sniffers were given one sample at a time. After examining it, the dogs had to signal if they detected the target odor. Kelly showed a higher accuracy of 81 percent here, while Ivy's result was 74 percent.

Comparing the dogs' achievements with questionnaires in which volunteers described emotions, the researchers found that one responded to anxiety and the other to displays of shame. Scientists hypothesized that Ivy's sense of smell could "tune in" to hormones associated with sympatho-adreno-medullary responses, one of which is adrenaline. Kelly, on the other hand, picked up the scent of hormones from the hypothalamic-pituitary-adrenal axis like cortisol.

According to the authors of the paper, this is important because the sensitivity of the sense of smell to hormones of the first group is necessary to warn of early symptoms of PTSD. The scientists intend to conduct additional experiments to confirm the assumption.

If the researchers succeed in what they have envisioned, their findings could find serious medical application in the therapy of patients with PTSD. However, given that only two of the 25 dogs were found to be fit enough for such tasks, finding personnel for such a method will not be easy.