Phys.org: “The levels of stress in dogs correlate with the stress of their owners, according to a new study from Linköping University, Sweden. The scientists believe that dogs mirror their owner’s stress level, rather than vice versa. The study has been published in the scientific journal Scientific Reports. Researchers at Linköping University have examined how stress levels in dogs are influenced by lifestyle factors and by the people that the dogs live with. Previous work has shown that individuals of the same species can mirror each others’ emotional states. There is, for example, a correlation between long-term stress in children and in their mothers. The recently published study arose from scientists speculating whether similar mirroring of stress levels over long time periods can also arise between species, such as between the domesticated dog and humans. The researchers determined stress levels over several months by measuring the concentration of a stress hormone, cortisol, in a few centimeters of hair from the dog and from its owner.

“We found that the levels of long-term cortisol in the dog and its owner were synchronized, 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…”