Are You Stressing Out Your Dog?

You—or, more particularly, your personality and your lifestyle—may be stressing out your dog. New research shows that the stress level in dogs mirrors the stress level in their owners.

Dogs, like people, suffer from the effects of stress. Stressors come in a variety of types, but one of the most important factors is how long the stress continues. Some stressors can be severe but short in duration (like when you safely survive a traffic accident), while others can be long-term (such as continuing financial difficulties). It is the long term stressors which are most dangerous since psychological research has shown that these can cause a variety of physical and mental problems. People under continuing stress are more likely to have cardiovascular and immune system difficulties and are also apt to suffer from depression and other psychological troubles. The same holds for dogs. In fact, the same types of pharmacological agents are used to treat stress in both humans and canines. To counteract the effects of continuing stress and depression in dogs, veterinarians often prescribe a canine equivalent of Prozac—beef-flavored, of course.

When behavioural researchers became interested in the study of stress in dogs, however they encountered some problems. Dogs are not verbal, so they can't tell us when they are feeling tense and anxious. That meant researchers had to rely on visible signs and signals. This included a variety of dog body language signs, such as how the dog's ears were postured, the activity of the dog’s tail, and whether the dog crouched, cowered or moved lethargically. While such signals can answer the yes or no question, “Is this dog stressed?”, they cannot provide a quantitative measure of just how stressed the dog is.

The breakthrough for the study of canine stress came when researchers recognized that dogs under stress secrete the same hormones that humans do. The critical marker for stress is the amount of cortisol that is released into the blood system by the adrenal glands, a crucial part of the body's response to different kinds of stressors. For example, an increased cortisol level can indicate a sharp increase in stress, such as from a sudden frightening event. For researchers, the concentration of cortisol is a wonderful tool since it is possible to determine, in real time, the amount of stress that the dog is feeling by taking blood samples, or more recently, by simply taking saliva samples—preferable since swabbing a dog's mouth does not add to his stress level.

However, suppose the researcher was interested in measuring the continuing stress level experienced by the dog over a period of days, weeks, or longer. This would require many saliva swabs to be taken over a long period of time, perhaps on a daily schedule. Not only is this a labour-intensive process, but the radioimmunoassay to determine the cortisol concentration in each sample is complex and costly.

Fortunately, a new technique has been developed. It turns out that some molecules of cortisol in the blood also tend to be incorporated into growing hair—or fur. As the hair grows, it captures an extended picture of the amount of cortisol in the body, and presumably, the amount of stress experienced by the individual over longer periods of time. Thus, a strand of hair becomes a sort of stress diary. Studies on humans have shown increased cortisol levels in the hair of individuals suffering from chronic pain, as well as people who are unemployed, and in those who have continuing depression. Based on such findings one can suppose that dogs living with long-term stress levels will similarly show greater amounts of cortisol in their fur.

Recognizing the usefulness of this measurement technique for determining extended stress levels was fundamental for a team of researchers headed by Lina Roth in the biology department at Linköping University in Sweden. The interesting thing about this methodology is that it allows the same measurement of long-term stress levels to be used on the dog's owners as well, letting researcher determine if there is any synchronization in the amount of stress that the dog and the human are experiencing.
 

"The big surprise came with the finding that people who are high on the personality dimension of neuroticism tended to have dogs with lower stress levels."
 

The research team studied 58 dogs, all Shetland Sheepdogs and Border Collies, and their owners. The dogs and humans were tested twice, once in the summer and once in the winter, with fur and hair samples taken and analyzed for their cortisol level.

The investigators knew that if they found any association in the ongoing stress levels of the humans and canines, the next question to answer would be why such a relationship existed. The dog owners filled out several different research questionnaires which were designed to give information about the personality of the dogs, their typical behaviours, and the lifestyle that the dogs most commonly experienced.

The major finding was that dogs and their owners indeed had similar stress levels—dogs with high levels of continuing stress tended to have owners with similarly high long-term stress levels. Dogs with low extended levels of stress tended to have owners who also seemed to be relatively stress-free.

There was a correlation between the stress levels of dogs and their owners, leaving the unanswered key question: what causes this association? To determine if the dog was influencing the owner or vice versa, the scientists took measures of the dog's personality, the human's personality, and their lifestyle. 

Statistical analyses clearly showed the dog's personality was not having an influence on the owner's stress level, however the personality of the human member of the pair did seem to be important. The researchers used a measure of what are called the “Big Five” dimensions of personality. You might find it helpful to use the acronym OCEAN which stands for openness, conscientiousness, extraversion, agreeableness, and neuroticism. In this particular piece of research, high scores on the dimensions of openness and conscientiousness caused an increase in the dog's stress levels while a high level of neuroticism caused a decrease.

Openness is a trait associated with imagination and the willingness to explore new things and enjoyment of new experiences. People who are low in openness tend to dislike changes and are most comfortable in familiar settings doing familiar things. Since dogs tend to enjoy routine and predictable situations this helps to explain why they are more stressed when their owner is high on this personality dimension.

People who are high in conscientiousness are well organized and tend to pay attention to detail. They really dislike messy things and are bothered when tasks are not finished or done poorly. As we all know, dogs are not bothered by details in most of their actions, and dogs tend to be messy. Furthermore, dogs often procrastinate or are slow at completing tasks. That means that having an owner who is high in this dimension and who therefore puts pressure on the dog to be more conscientious is apt to raise the stress level of the pair.

The big surprise came with the finding that people who are high on the personality dimension of neuroticism tended to have dogs with lower stress levels. Individuals who are high on the neuroticism trait tend to have mood swings, are anxious, and are susceptible to sadness and depression. My initial thought was that this kind of person should stress their dogs, which is the opposite of what the research shows. The authors explain their findings by saying that there is some indication that humans scoring high on neuroticism form a strong attachment bond to their dogs, and they also use their dog as a social support—meaning more interaction and physical contact. These behaviours simultaneously function as social support for their dog who benefits from loving attention and thus the stress level of both the human and the canine decrease.

In short, researchers concluded that long-term stress hormone levels are indeed synchronized between dogs and their humans, and it is the dogs who are responding to the stress levels of their owners rather than owners responding to the stress in their dogs. In other words, if your dog seems stressed, you may want to take a look in the mirror.