Didn't Even Blink: Dissociation, Complex Trauma Exposure and Decreased Startle Reactivity

The startle eyeblink reflex is thought to function as a means of orienting to salient stimuli, and, by proxy, sensitivity to threat cues. The absence or attenuation of this reflex may thus suggest disengagement from one's environment, potentially in circumstances when engagement is called for, and, therefore, may serve as a potential marker for dissociation as it occurs. The present study investigates whether individual differences in startle response magnitude and habituation are attributable to early and multiple trauma exposure, dissociation, and PTSD symptom severity. Fifty-four Black college students with at least one traumatic event completed self-report measures of trauma exposure, PTSD symptoms, and in-task dissociation, and underwent a standard acoustic startle task. Startle data were analyzed for quadratic trauma feature (symptoms/exposure) by time interactions in order to detect nonlinear decreases in reactivity. Participants with earlier trauma (before age 6) and greater in-task dissociation showed significantly decreased startle reactivity, but neither multiple trauma exposures nor PTSD were related to startle reactivity. Contrary to expectations of solely exaggerated startle reactivity, the group with early life trauma exposure and dissociative experiences had attenuated startle reactivity compared to their peers with later-onset exposure and lower dissociation. Data are consistent with the existing literature on DSM-5 Dissociative subtype of PTSD, and supports the notion that some symptomatic individuals may in fact benefit from greater engagement with their environments, which may counter a notion of habituation to stressors as a primary therapeutic goal.