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Post-Traumatic Stress Disorder

Do Service Dogs Help Military Veterans with PTSD?

Encouraging evidence from a new study.

New research from Purdue University's College of Veterinary Medicine in conjunction with Florida-based non-profit K9s for Warriors finds military veterans with PTSD do better on both physiological and psychological measures if they have a service dog compared to if they are waiting to receive one. The study provides preliminary evidence service dogs may improve well-being for veterans with Post Traumatic Stress Disorder (PTSD).

Danika Perkinson / Unsplash
Source: Danika Perkinson / Unsplash

When military veterans come back from war, between 5% and 20% are estimated to suffer from post-traumatic stress disorder.

According to the American Psychiatric Association, “Posttraumatic stress disorder (PTSD) is a psychiatric disorder that can occur in people who have experienced or witnessed a traumatic event such as a natural disaster, a serious accident, a terrorist act, war/combat, rape or other violent personal assault.”

Can service dogs help military veterans with symptoms of PTSD? One study from Purdue earlier this year looked at psychological symptoms in veterans with a service dog to those who were waitlisted to get one.

The veterans who had a service dog reported significantly fewer symptoms of PTSD and better scores for psychological well-being, coping skills, and other measures of well-being.

Writing about the study on Psychology Today, Dr. Hal Herzog wrote, “This research provides the best evidence we have that psychiatric service dogs may reduce PTSD in veterans.”

Now a second study, also from Purdue, looks at a physiological measure, too — differences in salivary cortisol between veterans with PTSD who have a service dog and those still on the waitlist.

According to Kerri Rodriguez, first author of the study:

“We found that military veterans with a service dog in the home produced more cortisol in the mornings than those on the waitlist. This pattern is closer to the cortisol profile expected in healthy adults without PTSD. Having a service dog was also associated with less anger, less anxiety, and better sleep.”

Like the previous study, the research was carried out in conjunction with K9s for Warriors. They provide service dogs to military veterans who have PTSD, traumatic brain injury, or military sexual trauma. The study looked only at veterans with PTSD.

K9s for Warriors takes shelter dogs and trains them to become service dogs. The dogs are a range of breeds including Labradors, Golden Retrievers, and mixed-breed dogs, and must be at least 24 inches tall.

As well as learning general obedience, the dogs learn specific commands that are designed to help veterans with PTSD. For example, “block” means to help the veteran get some personal space by standing sideways in front of them.

And because veterans with PTSD can be hypervigilant in crowds, another command the dogs are taught is “cover.” This means they position themselves behind the veteran and will warn of approaching people–essentially, they are watching their back. The dogs are also trained to notice signs of anxiety and will comfort and calm the veterans if needed.

When veterans are assigned a service dog, they attend a three-week training program to learn how to care for and interact with the dog, and how to maintain the dog’s training.

The new study looks at veterans with PTSD who wanted to have a service dog. The vets in the service dog group had had the dog for between 1 month and 4 years. The vets who were on the wait-list had been waiting from two and a half months to just over one and a half years. The final data set included 45 veterans with a service dog and 28 who were on the wait-list.

Participants were asked to provide saliva samples on waking up and 30 minutes later on two different days. They were reminded by text message.

The study looked at cortisol levels in saliva. We think of cortisol as a stress hormone, and it is often used as a physiological marker of stress. It is a measure of arousal and levels fluctuate during the day.

The scientists looked at the cortisol awakening response, the change in cortisol levels between first waking up and 30 minutes later. Normally, cortisol is low when we wake up, and increases by about 50% to 75% over the next 30 minutes. In people who are chronically stressed, this response is often much lower.

The scientists used two measures of salivary cortisol: the cortisol awakening response itself (i.e. the difference between the cortisol levels at the two time-points), and another measure (technically called area under the curve with respect to increase) that looks at rate of change over time.

The results showed both measures were bigger for the veterans with service dogs compared to the wait-listed veterans. This was still the case after taking account of other factors that can affect cortisol, such as the time of waking up, quality of sleep, and use of medication and alcohol. This suggests the veterans with a service dog had better levels of well-being.

Survey results also showed that veterans with a service dog had less sleep disturbance, lower levels of anxiety and anger, and less alcohol abuse than those on the wait-list.

These results suggest service dogs can help military veterans with PTSD both physiologically (as measured by cortisol awakening response) and psychologically.

The researchers are careful to say these results do not show causality. They do not show that a service dog cures PTSD, or do not explain the relationship between the physiological measures taken and PTSD symptoms. For that, more research is needed. Luckily, a longitudinal trial is already underway to investigate whether service dogs can help veterans with PTSD. The results will be eagerly awaited.


Rodriguez, K. E., Bryce, C. I., Granger, D. A., & O’Haire, M. E. (2018). The Effect of a Service Dog on Salivary Cortisol Awakening Response in a Military Population with Posttraumatic Stress Disorder (PTSD). Psychoneuroendocrinology.

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