The benefits of therapy dogs for various types of populations, including hospital patients, students, children learning to read, nursing home residents, and others, have been well documented, but how this work affects the dogs themselves has been less studied. Having made therapy dog visits with Chloe for over six years, I have known a number of teams that have stopped because the handler concluded a therapy dog was burning out. One handler told me that she took her boxer out of service because the dog had an expression that she had not seen before when a child picked up a fold from the dog’s back. “He was not happy. I could not risk that it might go further.”
Concern for stress in therapy dogs was expressed by James Serpell, Raymond Coppinger, and Aubrey Fine in 1999, and various research teams have been looking to identify and measure stress in dogs doing therapy work, with some studies being largely anecdotal, some behavioral, and some looking for chemical markers that might indicate whether therapy dog work is stressful, and when it is too stressful for the dogs. Although levels of oxytocin and insulin have been studied in the search for chemical profiles of stress, the studies discussed here were particularly focused on measuring levels of cortisol. These studies often included measurement of specific behaviors and generally—though not consistently—found that therapy dogs did not have higher cortisol levels while they were doing therapy dog work or had recently completed therapy assignments.
Cortisol is a steroid hormone secreted naturally in response to numerous mental and physical stimuli, some but not all of which are negative and stressful. Cortisol rises in response to sexual stimuli and activities such as hunting and guarding. Also, since dogs have long been valued for waking a village at night at the approach of intruders, it is possible that being approached and petted by strangers, as happens in therapy work, may produce some discomfort and raise cortisol. Short-term effects of elevated cortisol are useful in allowing an animal to regulate bodily responses to situations requiring energy and focus, but prolonged high levels can lead to stress-related diseases and have negative effects on an animal’s health. (Glenk et al., 2014) Therefore, research has begun to focus on a combination of behavioral indications and high cortisol levels to establish that a dog is under stress.
Research Issues
A number of questions have been posed by the research teams involved in this work, which are listed here with pithy summaries of the answers reported so far. After this summary of issues, I will attempt some additional elaboration on some important studies.
- Are cortisol levels higher while therapy dogs are working than when they are at home or in other environments? Some studies say yes, but an increasing number have found no significant difference during or after therapy work. It is not clear that a reconciliation of inconsistent results is yet possible or wise, but I will hazard some thoughts on why the disparate results may have been reached.
- Do the length and frequency of therapy dog work sessions affect cortisol levels? Most studies looked at dogs doing nearly identical regimens of therapy work, though there may be indications that particularly long and frequent assignments lead to elevated cortisol levels.
- Does providing breaks to therapy dogs during work sessions avoid cortisol levels elevating during work days? A study that was designed to answer this specific question found that the breaks made no significant difference in cortisol levels between a group of dogs that got breaks and a control group that did not.
- Does working on leash increase cortisol levels for therapy dogs as opposed to working off leash? A recent study found that working on leash resulted in higher cortisol levels. I will discuss policy implications.
- Are dogs stressed when working with specific target populations? There is some evidence that working with children under age 12 is stressful for dogs, but other groups, such as nursing home residents, Alzheimer’s patients, and drug addicts do not seem to increase canine cortisol levels.
- Does positive reinforcement as a training approach reduce stress in subsequent therapy work by dogs? A number of studies emphasize the use of positive reinforcement in training dogs for therapy work, but this has not been isolated as a factor in identifying which dogs will be more stressed by the work. Because of ethical considerations, I doubt that it will be.
- Are particular canine behavioral patterns correlated with higher cortisol levels? Since some studies did not find higher cortisol levels from therapy work by dogs, correlations could not be provided between behavioral patterns and higher cortisol levels. Nevertheless, a number of research teams have proposed lists of behaviors that should be recorded when seeking to verify that higher cortisol levels indicate stress rather than arousal from some other stimulus. A standard list of such behaviors should be developed so that studies from various research groups can be correlated.
Before looking at individual studies, it is appropriate to provide a summary of their approaches and most important results, which is attempted in the following table. The lead authors and dates of publication are listed in the first row, followed by summary characteristics of the teams, their training, the facilities where they work and what therapeutic functions they have. Because one paper in particular raises the question of whether use of a leash may be a significant stress factor, a row is provided for what information is available from each study in this respect. Finally, a summary of the behavioral and cortisol results is provided.
Figure 1. Characteristics of Dogs, Training, Facilities, Activities, and Results of Cortisol Studies
Figure 1. Characteristics of Dogs, Training, Facilities, Activities, and Results of Cortisol Studies
Paper | Haubenhofer & Kirchengast, 2006 | Piva et al., 2008 | King et al., 2011 | Glenk et al., 2013 | Ng et al, 2014 | Glenk et al., 2014 |
Number of dogs/teams | 18 | 1 | 27 selected (data from 21) | 21 | 15, but one team eliminated because of atypical results | 5 dogs 3-10 years old |
M/F | 15 (4 spayed)/3 (1 neutered) | 1 female intact (sometimes in heat) | 14/13 | 7/14 (all spayed) | 8/6, all fixed or spayed | 3 (2 fixed)/2 (1 spayed) |
Certification/training | Teams members of Tiere als Therapie | Basic obedience commands | Certified by Therapy Dogs, Inc. (Cheyenne) | Austrian AAI organization, certified dogs had ? 1 year experience in mental healthcare facilities | Vet Pets, Therapy Dogs International, AAA sessions, averaging visits from an 1 to 10/ month | Certified in Italy for AAI work, all with ? 2 years working experience; all trained with positive reinforce-ment and averaging ? 1 visit/ month |
Facility/ population | Various facilities (hospitals, rehabilitation centers, retirement homes, schools) | Alzheimer’s patients | Edward Hospital, Naperville, Ill., most patients 41-60 years old, but some children | 8-10 patients | Students in common area of U. Penn. Dormitory, 30 to 56 individuals in same room during study breaks | Drug-addicted inpatients |
Activities | Dogs participate in “all types of work in AAA and AAT,” ranging from 1 to 8 hours (!) | 20-minute AAA sessions | 2-hour shifts, involving petting, hugging, watching the dog (AAT) | 50-60 minute AAI sessions (~AAT) | Highly structured petting, scratching interactions in 60 minute sessions | Multi-professional animal assisted intervention (similar to AAT); sessions 55-60 minutes |
Frequency | Variable number of sessions, sampling over 3 months | 3-4 times/week | 2 sessions/ week | 1 time weekly for 8 weeks | Two 2-week periods during March & April 2012 | 1/week with 8-10 participants (and 1 dog and 2 therapists) |
Use of leash | Not described | Allowed to roam free | Certifying organization requires use of leash, so presumably applied here | For experiments, 7 certified dogs were on leash and 7 were off; dogs in training were on leash | Off leash at home, on leash in novel and AAA environments, but could be attached to collar, harness, or head collar | Off leash |
Reward | Not described | Praise, allowed to be free in garden and chase lizards | 2-minute quiet-play time-out session (found not t
 
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