Responses to Aversive Acoustic Stimuli in Posttraumatic Stress Disorder: Moderation by the Presence of a Service Dog in Training.

Psychophysiologic responses to a series of aversively loud tones have discriminated groups with posttraumatic stress disorder (PTSD) from those without in multiple studies. Using a within-subjects design, we examined whether such responses were moderated by repeated presentation, by the severity of PTSD-related hyperarousal, and by the custody of a service dog in training. The US military veterans engaged in residential treatment for PTSD and concurrently participating in a service animal training intervention were administered a loud tones protocol over four to six weekly sessions. During approximately one-half of sessions, participants were accompanied by their assigned service dog in training. Skin conductance responses (SCRs) and heart rate responses to the tones were quantified and modeled. Dog presence was associated with smaller SCRs and cardioacceleratory responses to aversively loud tones. In the case of SCRs, dog presence moderated the amplification of those responses in participants endorsing more severe hyperarousal and accelerated habituation over sessions. Moderation of autonomic responses to aversive stimuli by dog presence may offer insight into reports of "calming" provided by PTSD patients when queried about benefits they received from service dogs. Objective psychophysiological measures may inform studies of the physical and mental health benefits associated with service and pet dog companionship.