Service dogs prove effective in identifying PTSD-related stress markers through human breath

Service dogs prove effective in identifying PTSD-related stress markers through human breath

In a recent study published in Frontiers in Allergy, researchers examined whether dogs can detect potentially stress-related volatile organic compounds (VOCs) in the breath of trauma survivors (54% with post-traumatic stress disorder (PTSD)) who were exposed to individualized trauma signals.

background

PTSD, a mental illness, is characterized by persistent stress reactions to life-threatening situations. Service dogs are supplemental treatment dogs that are permanently housed with patients and trained to help them.

There is evidence that the use of service dogs results in significant long-term reductions in PTSD symptoms, with intrusive and hyperarousal symptoms having the greatest impact. Dogs have unique abilities to detect volatile stressors, which can benefit predator species.

Chronic amygdala and overactivity of the stress response are hallmarks of PTSD and anxiety disorders, with the sympathetic-adrenal-medullary axis (SAM) and the hypothalamic-pituitary-adrenal (HPA) axis playing critical roles in restoring balance.

About the study

In the present study, researchers examined whether dogs could detect early-onset PTSD episodes in breath samples from people with prior trauma when exposed to trauma reminders. They examined training dogs to use olfactory cues to detect the early onset of post-traumatic stress disorder (PTSD) and hyperarousal symptoms.

The team collected breath samples from 26 people between the ages of 20 and 53 during 40 sessions in relaxed (control sample) and agitated states due to trauma cue exposures (target sample).

They showed two odor detection dogs of donor samples in the two alternative forced choice (2AFC) discrimination and no/yes detection tasks.

The researchers used signal detection theory (SDT) to assess the dogs' sensitivity, specificity, accuracy, and response bias. They recruited human donors from research on the neurocognitive processes underlying the links between trauma and cannabis use.

Donors aged 19 to 65 years were free of adverse mental illnesses reported using the Life Events Checklist (LEC), had more than one Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), Category A criteria for PTSD, and had used more than one gram of cannabis per week in the previous month.

The Self-Reported Posttraumatic Stress Disorder Checklist (PCL-5) assessed symptom severity and the percentage of individuals likely to have PTSD.

The Clinician-Administered PTSD Scale (CAPS-5) identified PTSD and provided an additional measure of PTSD symptom severity (CAPS-5 Symptom Count).

The researchers recruited 25 service dogs of various types and began scent recognition training at the Dalhousie Canine Olfaction Laboratory. Two dogs, Callie and Ivy, demonstrated consistently accurate performance, indicating that they could detect the target odor and were prepared for testing with donor samples.

The team used the Positive and Negative Affect Schedule (PANAS) and the Visual Analog Scale (VAS) to measure donors' emotional state after trauma and cannabis exposure, respectively. The dogs worked in the lab in two-hour shifts once a week, using positive reinforcement training methods.

They examined the relationship between the dog's performance and the severity of PTSD symptoms or diagnostic parameters. They also examined the dogs' responses to cannabis-related VOCs and correlated the severity of cannabis use disorder (CUD) symptoms and the donors' cannabis appetite with exposure to traumatic stimuli.

Results

Callie and Ivy achieved 90% accuracy on both pairs of samples in the discrimination test, while the recognition test yielded 81% and 74% accuracy, respectively.

Further investigation of dogs' olfactory performance in relation to human donors' self-documented emotional responses to trauma memories revealed that the dogs were able to detect separate endocrine stress signals.

One dog's performance was associated with human donors' self-documented fear responses, while the second dog's performance was associated with donors' self-documented shame responses.

Based on the relationships between dogs' performances and measurements documented by human donors themselves, the researchers hypothesized that the volatile organic compounds (VOCs) detected by the dogs developed from the sympathetic-adrenal-medullary axis (adrenaline and norepinephrine) in one of the dogs and the hypothalamic-pituitary-pituitary system. adrenal cortex (glucocorticoids) for the second.

The mean PCL-5 score was 45, above the threshold for a probable PTSD diagnosis. Eighteen people (69%) were above the threshold. The CAPS-5 interview confirmed the PTSD diagnosis in 14 (54%).

The mean CAPS-5 symptom count was 11, suggesting that the typical donor reported 11 PTSD symptoms. The average value was 11.4, which was above the threshold for dangerous cannabis use. Fourteen individuals exceeded the threshold for a probable CUD diagnosis (54%).

Exposure to traumatic cues during interviews increased donors' negative emotions, particularly fear of the condition. Ivy performance was positively associated with donor state anxiety, PANAS negative influence, and multiple PANAS negative effects.

Callie's performance was positively correlated with the PANAS trauma cue “ashamed.” Both dogs were able to recognize the target scent in different stressful situations.

The study showed that dogs could detect VOCs emitted by people with previous trauma episodes who are distressed due to post-traumatic stress disorder or hyperarousal symptoms.

The study results are consistent with previous research showing dogs' ability to detect tension in humans through their sense of smell. The researchers expanded the study to include trauma, with all donors reporting traumatic experiences and more than half suffering from PTSD.

They found that dogs can generalize olfactory indicators of this stress response, supporting the concept of PTSD-aware dogs.

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