Studies & Research
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Nancy Dreschel has long been interested in the ways people and animals interact. She got her degree in veterinary medicine from Cornell University, but her lifelong interest in behavior led her to return to graduate school five years ago to pursue a PhD in biobehavioral health at Penn State University. She, her husband and their two sons share their home with one dog, two cats, four fish and a mouse.
In her recent study, "Physiological and behavioral reactivity to stress in thunderstorm-phobic dogs and their caregivers,"* Dr. Dreschel investigated stress responses—pacing, salivating, panting, trembling, whining, hiding, increased salivary cortisol levels—of dogs with thunderstorm phobia and their human caregivers when both were exposed to simulated thunderstorms. Listening to a simulated storm elicited behavioral and physiological responses in nearly all the dogs, but not in their human caregivers. The way the dogs responded was not influenced by their caregivers’ reactions, or by how close the relationship was between person and dog. But dogs who lived with other dogs had less change in salivary cortisol levels and a more complete return to baseline levels by 40 minutes after the simulated thunderstorm than did dogs in single-dog households. Dogs in multidog households had slightly higher baseline levels of salivary cortisol. (For more, see “Is a Dog a Dog’s Best Friend?,” Jan/Feb 06.) The Bark recently interviewed Dr. Dreschel about her work.
Bark: How did you get interested in this subject?
Nancy Dreschel: My colleague Dr. Doug Granger, and the Behavioral Endocrinology Laboratory at Penn State are well known for their research on salivary hormone measurement, particularly in children. I was struck by the ease of saliva collection and thought that it would be a nice, noninvasive way to measure stress in dogs as well as in people. Thunderstorm phobia seems to be particularly frustrating for people and particularly stressful for dogs. I feel strongly about the humane use of animals and am interested in developing tools to measure stress in welfare situations.
B: How do you define stress?
ND: In order to define stress, I think you first have to understand that all aspects of living systems are [intended to be] in balance. Things constantly affect our physiological and psychological states, and our bodies respond to keep everything in homeostasis, or equilibrium. I define stress as being anything that knocks this off, including immune stressors (being exposed to a virulent disease), environmental stressors (being wet and standing outside on a 20-degrees-below-zero day) or mental stressors (enduring a thunderstorm if you are terrified of them).
B: Could baseline cortisol levels be affected by the difficulty that some people had in collecting the samples—wouldn’t the “phobic” dog demonstrate stress simply as a result of the collection process itself?
ND: Specimens collected on the control day did not show any increase in cortisol, which is what would be expected if the collection method itself caused stress. [On the control day, there was no simulated thunderstorm.] It should be noted that these dogs were behaviorally quite normal, other than their very specific fear of storms.
B: Are you familiar with any other studies that have measured the cortisol levels in multidog households?
ND: No—this was the first (and only) study I know of to measure cortisol in a home situation. Salivary cortisol has been measured in shelters and research facilities, however.
B: What sorts of clinical applications do you imagine could result from your research on dogs with thunderstorm phobia?
ND: Collecting saliva from dogs is a minimally invasive procedure that can be done by regular people in a number of different settings. I could see this procedure being used in studies of dogs with anxiety, in stressful situations and in welfare applications. I also think it could possibly be used to determine if dogs on medication for anxiety or fear are responding physiologically as well as behaviorally.
B: What kind of treatment program do you advise for people whose dogs have thunderstorm phobia?
ND: I recommend a number of individualized programs for dogs with thunderstorm phobia, including offering a “safe” place to go (covered crate, basement, etc.), behavior modification (counter-conditioning and desensitization), pheromone therapy and anti-anxiety medication. Many dogs require medication in order to calm down enough to be able to learn new behaviors.
B: What do you think is the most significant result of the study?
ND: I think the most significant result is finding the degree of increase in cortisol that these dogs experienced and the fact that it lasted so long. When I think of the number of dogs who experience similar stressors (which might range from a car ride to panic when left alone), I wonder if all these experiences are accompanied by a similar physiological reaction. We know by their behavior that some dogs become upset by certain situations, but these results show that a physiological response that could have adverse health effects is also occurring.
B: Why do you think the presence of other dogs in the household had an effect on cortisol reactivity in dogs with thunderstorm phobia? Is the higher baseline a key factor in the faster return to near-baseline levels?
ND: I’m not sure why living with other dogs had an effect in our subjects. Their baseline cortisol levels were somewhat higher to begin with, which could indicate they were under more stress on a regular basis. I think it is likely that something about living with other dogs mediates how their stress-response works. Maybe the day-to-day interactions better prepare the hypothalamic/pituitary/adrenal axis for response to major stressors.
I would emphasize that the dogs that lived with other dogs didn’t “seem” calmer—behaviorally, there was no difference. Because this was a fairly small study, it is hard to draw many conclusions about the multiple-dog findings.
B: Did the other dogs actually do anything to alleviate stress in these dogs?
ND: What struck me was a total lack of “comforting” as we define it in human terms, from the other dogs in the household. We think of comforting as having a shoulder to cry on, a hug, a gentle word or listening ear. Many of the dogs in our study (both those who lived with other dogs and those who were the only dog) sought out this type of comforting from their human companions. However, there was very little, if any, physical contact between the dogs in this study. Many of the non-subject dogs in the household weren’t even present during the procedure—the caregivers had isolated them in other rooms so they only had to deal with the subject dog.
B: Our magazine promotes adoption of shelter/rescue dogs, and likes to think that dogs benefit by living in multidog households (with compatible canines, of course). Is there any scientific basis for this?
ND: I think our research provides some evidence to support this statement. However, I do not recommend that people with storm-phobic dogs run out and obtain another dog, thinking that will make their dog’s problem go away. The dogs who lived in multidog households still had thunderstorm phobia and severe behavioral responses, despite the fact that they lived with other dogs.
*Published with co-author Douglas Granger, PhD, in Applied Animal Behaviour Science 95: 153–168.