Is your dog stressed out? Maybe you're the one who needs a belly rub.
New research finds that throughout a dog's life, the stress levels of a canine and his or her human tend to rise and fall together. In fact, stress in a dog appears to be more closely linked to the stress of its owner than it is to the dog's own temperament.
In the 15,000 years that humans and dogs have lived together, dependence and mutual affection have deepened our bond. And science has long established that "emotional contagion" between us and our canine pets is very real.
The new study, published Thursday in the journal Scientific Reports, is the first to find that this contagion is not fleeting. It also suggests that a dog owner's mental well-being shapes the pet's emotional health in a uniquely powerful way.
Much has been made of the health benefits that dogs offer to humans. Our heart rates and blood pressure routinely decline in their presence. Our levels of circulating oxytocin -- often referred to as the "love hormone" -- rise when we gaze into a dog's eyes. Probably because they walk more, and also socialize more, dog owners live longer and healthier lives than those without a canine companion.
But the latest research demonstrates the extent to which that psychological connection is a two-way street. Return from work in a consistently foul mood and even if you don't actually kick the dog -- please don't! -- your furry friend's stress level is likely to rise accordingly.
Researchers recruited 33 Shetland sheepdogs and 25 border collies and measured levels of the stress hormone cortisol in their hair and the hair of their human guardians. Unlike cortisol levels in the bloodstream, levels in hair don't vary widely over a day, week or month. Since it builds up slowly, it offers a clearer picture of stress levels over time.
The research team from the University of Linkoping in Sweden also had each participating dog owner -- all of whom were women -- complete a battery of questionnaires that measured not only their own personality traits, but the temperament of their dogs.
When the study authors looked for alignment between the temperaments of dog owners and their pets, they found no significant similarities or differences. There was little to suggest either that humans "pick" dogs that match their personalities, or that, like the stereotypical old married couple, they grow more similar over time.
But when the researchers examined the hair samples, they found clear evidence of emotional convergence between dog and human.