Anyone who has had the privilege to own a dog knows that the consistent presence of a companion animal can be incredibly calming and therapeutic; at least, if said dog is a good boy or girl.
For this reason, specially trained service dogs have recently become an integral part of the recovery process for individuals struggling to function in their daily lives because of post-traumatic stress disorder (PTSD).
And though the anecdotal evidence is quite overwhelming – many combat veterans have reported that their service dog restored a will to live after intense depression drove them to thoughts of suicide – researchers have been looking for objective proof that this expensive intervention (each dog/veteran placement costs $20,000-30,000) is effective.
So, a team led by Maggie O’Haire at the Purdue University Center for the Human-Animal Bond stepped in to fill this need. Their paper, published in Psychoneuroendocrinology, examined the physiological and psychological impact of living with a service dog by comparing answers from a mental health survey and levels of the stress hormone cortisol among 73 veterans who had acquired PTSD when serving in the military after the 9/11 attacks. Forty-five of these subjects had a service dog, and the other 28, individuals who were on the waitlist to receive one, served as controls.
“Our previous research suggests that the presence of a service dog reduced clinical PTSD symptoms and improved quality of life,” O’Haire said in a statement. “In this study, we wanted to determine if those beneficial effects also included changes in the physiology of stress.”
The authors chose to measure participants' cortisol levels in the morning in order to quantify the cortisol awakening response (CAR) – a known phenomenon in which the adrenal gland secretes more circulating cortisol soon after an individual wakes up in the morning. Most healthy adults display a CAR, yet the link between this hormonal release pattern and psychological well-being remains poorly understood. For the study, O’Haire and her team instructed participants to create a saliva sample immediately after waking up and again 30 minutes later on two consecutive weekdays.
Interestingly, analysis of the samples showed that people with service dogs had a higher uptick in cortisol during that half-hour period than those without a dog. Because CAR is a normal physiological process, the authors speculate this pattern could indicate the dog-owning individuals are actually less chronically stressed. Yet judging from the available data about CAR, that hypothesis is somewhat of a leap.
On the other hand, the survey findings clearly demonstrated that the service dog owners had a lower severity of PTSD symptoms – anxiety, anger, sleep disturbances, and alcohol abuse – compared with the waitlist participants.
“These findings present exciting initial data regarding the physiological response to living with a service dog. However, the study did not establish a direct correlation, on an individual level, between cortisol levels and levels of PTSD symptoms, and further study is needed. It is important to keep in mind that service dogs do not appear to be a cure for PTSD,” O’Haire said.
Her team has already begun a large-scale trial that follows PTSD-afflicted veterans with and without dogs for a longer period of time.