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.