The cortisol awakening response in a 3 month clinical trial of service dogs for veterans with posttraumatic stress disorder

Recent literature suggests that service dogs may be a valuable complementary intervention option for posttraumatic stress disorder (PTSD) among military veterans due to the potential influence on stress response dysregulation. The aim of this short-term longitudinal study was to quantify the impact of service dogs in US military veterans with PTSD with particular attention to the cortisol awakening response. A sub aim of the study was to empirically evaluate the physiological effects of PTSD service dogs on veteran partners. We conducted a clinical trial (ID: NCT03245814) that assessed the cortisol awakening response for 245 participants at baseline and 3 months follow-up across an intervention group (service dog: veterans n = 88, partners n = 46) and control group (usual care: n = 73, partners n = 38). A total of N = 161 veterans and N = 84 partners collected whole saliva samples via a passive drool collection immediately upon waking, 30 min after waking, and 45 min after waking on three consecutive weekdays at baseline and again at follow-up. Mixed model repeated measures (MMRM) with a fixed effect of the intervention group (service dog or control) were utilized. Covariates considered for the model included time of awakening, sleep duration, sleep efficiency, prior day experiences (measured via ecological momentary assessment), traumatic brain injury, age, gender, race, ethnicity, socioeconomic status, smoking status, alcohol use, physical health, and body mass index. A total of 3951 salivary samples were collected (veterans: 2613, partners: 1338). MMRM results demonstrated that veterans with a service dog had a statistically significant higher cortisol awakening response, including the area under the curve with respect to both increase (AUCi, β = 1.46, p = 0.046) and absolute increase (AINC, β = 0.05, p = 0.035). Results were not statistically significant for partners. Findings suggest that veterans with service dogs have a higher, less blunted CAR in comparison to veterans receiving usual care alone. In veterans with a blunted morning cortisol response, service dog placement could help boost their morning cortisol response.