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Hidden Ways Your Pet Can Suffer From Your Stress

Analysis by Dr. Karen Shaw Becker

pet stress causes

Story at-a-glance -

  • Recently published research that used cortisol levels in hair shows that long-term stress in humans can transfer to their dogs
  • The study also suggests that stress synchronization is especially pronounced in owners with dogs involved in canine competitive events
  • The study was limited to Border Collies and Shetland Sheepdogs; the researchers hope to expand their investigation to include other breeds
  • Earlier studies have shown that dogs pick up on human emotions through their eyes, ears, and noses, and that the odor of human fear can trigger a fearful response in canine companions

Here’s yet another reason (as if you needed one) to get serious about managing stress in your life: your dog’s health. According to recently published research, long-term stress in dog parents can transfer to their canine companions.1

The study, titled “Long-term stress levels are synchronized in dogs and their owners,” was conducted by a team of scientists at Linkoping University in Sweden. The experiment involved 58 owners of either Border Collies or Shetland Sheepdogs, and the researchers analyzed cortisol levels in hair from both the owners and their dogs.

Cortisol is a hormone released into the bloodstream in response to stressors such as depression, excessive exercise, and unemployment, and is ultimately absorbed by and can be measured in hair follicles.

Cortisol Levels Suggest Dogs and Their Humans Are in ‘Stress Sync’

The researchers discovered that the cortisol level patterns in the humans and their dogs closely matched in both winter and summer months, which suggests their stress levels were in synch.

The scientists haven’t yet nailed down exactly what causes the synching of cortisol levels between dog parents and their pets. However, interestingly, the synchronization effect appears stronger between owners of competitive dogs than between owners of regular family dogs.

According to Roth, the bond that develops between an owner and a competitive dog during training may intensify the dog’s emotional reliance on the owner, which in turn could increase the degree of cortisol synchronization.

In an email to STAT News, the director of animal behavior with the Nebraska Humane Society, Alicia Buttner, who believes the study results are no surprise, stated:

“New evidence is continually emerging, showing that people and their dogs have incredibly close bonds that resemble the ones that parents share with their children.”2

The study authors believe owners influence their dogs vs. the other way around, because certain human personality traits (e.g., neuroticism, conscientiousness, and openness) appear to affect canine cortisol levels.

In addition, it’s possible this mostly one-way influence is because dog owners are the proverbial “center of the universe” to their pets, whereas humans generally have broader social networks.

Cortisol Levels Are a Measure of Response to Both ‘Bad’ and ‘Good’ Stressors

Buttner believes we don’t have enough evidence yet to assume the influence only goes one way.

“It’s not just as simple as owner gets stressed, dog gets stressed,” she said.

There are multiple factors that affect both human and canine stress levels, some of which can actually alleviate stress rather than cause it. Cortisol levels aren’t always a measure of negative stress. In dogs, they can also be in response to positive stressors, such as a ride in the car or a hike in the mountains.

The Linkoping University researchers hope to follow up this study with an investigation into how other dog breeds react to their owners as measured by their cortisol levels. In the meantime, since dogs who play more show fewer signs of stress, Roth suggests dog parents “just be with your dog and have fun.”

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Dogs Pick Up on Our Emotions With Their Eyes, Ears and Noses

Our canine companions absorb our stress by sensing our emotions, and science has now confirmed that they not only see and hear human emotions, but also use their incredible sense of smell to inform them about how their humans are feeling.

Recently, I had the privilege of interviewing a team of university researchers in Italy and Portugal who set out to answer this question: “Do human body odors (chemosignals) produced under emotional conditions of happiness and fear provide information that is detectable by pet dogs (Labrador and Golden retrievers)?”3

For the study, 8 human study volunteers watched a 25-minute video designed to provoke emotional states of either fear or happiness. The volunteers’ sweat was collected on pads as they watched the video, and then the samples were pooled to obtain composite “fear sweat” and “happiness sweat” samples. There was also an unscented control sample.

The 40 study dogs were Labs and Goldens fitted with heart rate monitors. Each dog was placed in a small room with his owner and a stranger who had not provided a sweat sample. The two people were seated, reading magazines, and not purposely interacting with the dog.

The samples (either fear or happy sweat, or no scent) were diffused into the room from an open vial containing the sweat pads. The dogs were able to sniff the vial itself, but they weren’t able to directly touch the pads.

Behind the scenes, for 5-minute periods the researchers evaluated the dogs’ heart rate, body language, movements toward and away from the owner and the stranger, and stress-related behaviors. To goal was to learn whether the dogs would show a consistent set of behaviors in response to the three conditions.

Dogs Are Stressed by the Smell of Human Fear and Become Fearful in Response

The dogs exposed to the happy sweat sample had fewer and shorter interactions with their owners, and more interactions with the strangers in the room. This indicates the dogs felt relaxed enough to check out strangers and didn’t need to seek reassurance from their owners.

In contrast, the dogs exposed to the fear sweat sample displayed more frequent and longer-lasting stress-related behaviors, in some cases, for the entire 5-minute period. These dogs also sought out their owners rather than the strangers, indicating they were looking for reassurance because they felt stressed.

The thing that amazed me, as I watched the dogs’ behavior from a monitor outside the room, was how quickly the dogs picked up and reacted to the fear samples; it was almost immediate. And although the sweat samples were blinded (the researchers didn’t know which sample they were testing), it was clear from the dogs’ behavior which samples contained “fear sweat.”

The dogs exposed to the fear sweat sample also had consistently higher heart rates than the dogs exposed to the happy sweat sample and the control sample.

“While the dogs were clearly responding emotionally to the scent of fear,” writes dog expert Stanley Coren Ph.D., “it seemed as though their response mirrored the emotion that they were detecting in that they were acting in a fearful manner themselves.

There was no evidence of aggression toward either the owner, the stranger, or the scent dispensing apparatus.”4

A bigger question for me, as a veterinarian, is how long-term exposure to human stress and emotional imbalances in the home (fear, anger, frustration, etc.) impact our pets’ health without our knowledge. When Rodney Habib and I were working on our dog cancer documentary, almost every expert we interviewed brought up the role of stress in canine disease — a topic that hasn’t been studied.

These studies bring up the question of how negative human emotions play into health and disease patterns in pets. Hopefully, we’ll begin to answer these important questions in the near future and in the meantime, this is reason enough, in my opinion, to be conscientiously aware of the emotional health and wellbeing of every family member on a daily basis.