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A study published by Scientific Reports in June 2019 has found that when you are stressed, your dog gets stressed, too.

The authors of the study, a team of scientists based in Sweden, looked at levels of the stress hormone cortisol, by analysing hair samples from dogs and their owners. Cortisol is stored in hair as it grows in proportion to the amount in the blood, enabling measurement of how stressed someone has been over the months before the sample is taken.

Females More Sensitive

Long paper short: the 58 dogs in the study were all found to have increased cortisol levels if they had owners who were also stressed.

What’s more, female dogs were more sensitive to their owners than male dogs, the study found, especially if the owners had been classified as "neurotic personalities" in personality surveys. If the owners had "conscientious" as a personality trait, however, it was the male dogs that seemed to become more stressed.

The study authors wrote: "Emotional contagion, the mirroring of emotional or arousal states between individuals, is commonly seen among group-living species, for example as a synchronisation of acute stress responses."

Mirror Effect

In addition, the report says: "Our results show that long-term stress hormone levels were synchronised between dogs and humans, two different species sharing everyday life. This could not be explained by either physical activity or by the amount of training.

Since the personality of the owners was significantly related to the HCC of their dogs, we suggest that it is the dogs that mirror the stress levels of their owners rather than the owners responding to the stress in their dogs."

Two things to note is that, first of all, coincidentally, all the dog owners studied were female. Secondly, the stress levels of the dogs did not seem to affect the stress levels of the owners, so it's a one-way street.

Either way, stress has now been proven to be contagious.

* This article was updated on 8 July 2020. It first appeared in Pets Magazine, 6 July 2019.