Long-term stress in dog owners is associated with higher stress levels in their dogs, according to a study involving 58 dogs and their owners published in Scientific Reports.

Lina Roth and colleagues measured the hair cortisol concentration of 33 Shetland sheepdogs and 25 border collies and their human owners to determine their stress levels over a year. They found that when cortisol levels were elevated in humans, they were also elevated in their dogs - and especially in female dogs. This suggests that stress levels may have been synchronized in dogs and their owners. The association between stress in dogs and humans was also observed in both summer and winter, suggesting that seasonal fluctuations in cortisol levels did not affect the synchronization of stress.

The authors also asked the owners to complete two validated questionnaires, assessing traits such as excitability, responsiveness to training, aggression or fearfulness in dogs, and personality traits such as extraversion, agreeableness, or neuroticism in the owners. They found that the dogs’ personalities (as categorized by their owners) had little effect on their owners’ hair cortisol concentration. However, personality traits of conscientiousness and openness in the owners were associated with an increase in the dogs’ cortisol levels, and the trait of neuroticism was associated with a decrease in the dogs’ cortisol levels. This suggests that dogs may mirror the stress level of their owners rather than the owners responding to stress in their dogs.

These findings provide further evidence to support the strength of the relationship between humans and dogs, and may also be relevant to improving dog welfare, according to the authors.