Simply put, the closer you are to your dog, the more likely it may be to pick up on your stress.
When dog owners go through a stressful period, they're not alone in feeling the pressure - their dogs feel it too. It also suggests that a dog owner's mental well-being shapes the pet's emotional health in a uniquely powerful way. What's more, dog bites are an issue of increasing importance to society. Our levels of circulating oxytocin - often referred to as the "love hormone" - rise when we gaze into a dog's eyes. The owners and the dogs provided hair samples on two occasions separated by a few months.
But the latest research demonstrates the extent to which that psychological connection is a two-way street.
In examining the relationship between dog owners and their canine companions, Swedish researchers examined 58 individuals who owned Shetland sheepdogs or border collies that were either defined as regular "pet dogs" or "actively competing dogs". Cortisol is stored in hair as it grows in proportion to the amount of cortisol in blood.
One big question: Could dogs also influence human 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.
Though the seasons can impact one's cortisol levels, the research team did not find a difference in the mirroring of HCC levels between summer and winter.
Roth said she was surprised to find there were few associations between a dog's own personality and its long-term stress level, while an owner's personality appeared to have a strong effects on their pet's stress level.
"We found that the levels of long-term cortisol in the dog and its owner were synchronised, such that owners with high cortisol levels have dogs with high cortisol levels, while owners with low cortisol levels have dogs with low levels", says Ann-Sofie Sundman of the Department of Physics, Chemistry and Biology (IFM) at LiU, principal author of the study and newly promoted doctor of ethology.
They examined hair from the dog owners and their canine pals, looking at the concentrations of a hormone called cortisol, a chemical released into the bloodstream and absorbed by hair follicles in response to stress.
But they didn't. Canine cortisol levels did not seem to rise and fall with their position on the temperamental spectrum from fearful to calm. This led the researchers to believe that dogs mirror owners' stress levels, and not the other way around. "We suggest that dogs, to a great extent, mirror the stress levels of their owners", the scientists write in the journal.
The new research suggests some intriguing trends for researchers to explore in the future. It is suggested that the reason for the differing effects of neuroticism may be that females of many mammal species are more responsive to the emotions of others, causing the female dogs to be directly affected by the owners' anxiety levels.
Roth, a biologist who specializes in canine and equine cognition, said her group's past research with German shepherds has found that play and similar affectionate interactions are the key factor in tamping down dogs' anxieties. And somehow, their dog just knew something was wrong and responded with a loving gesture. "Have fun with your dog".