Autonomic and cortical reactivity in acute and chronic posttraumatic stress

Abstract

This study investigated attention (P300 amplitude) and orienting (skin conductance amplitude) to auditory tones in a standard oddball task in early trauma-exposed groups (Acute Stress Disorder: ASD) (n = 12) or no ASD (n = 13), compared to individuals with chronic posttraumatic stress disorder (PTSD) (n = 17) and non-trauma-exposed controls (n = 17). Individuals with ASD displayed significantly higher SCR and P3 amplitudes to target tones than individuals with PTSD, non-traumatized controls, and traumatized controls. These findings suggest that attention and orienting responses are greater to neutral, task-relevant target tones in ASD than PTSD and traumatized and non-traumatized controls.

Introduction

Deficits in attention are commonly reported in Posttraumatic Stress Disorder (PTSD: Vasterling and Proctor, 2011). The P300 component of the Event-related Potential (ERP) is thought to reflect the allocation of attentional resources (Polich and Kok, 1995). P3 amplitude is reduced to neutral target stimuli in PTSD (McFarlane et al., 1993, Felmingham et al., 2002), but increased to trauma-relevant or novel stimuli (Attias et al., 1996, Kimble et al., 2000, Karl et al., 2006). It has been suggested that reduced P3 amplitudes to neutral target stimuli may be related to trauma exposure rather than PTSD status (Karl et al., 2006, Kimble et al., 2010). Kimble et al. (2010) found that trauma exposure, but not PTSD symptom severity, predicted reduced P3 amplitude. However, many participants did not reach criteria for PTSD in their study. Kimble et al. (2010) noted that most ERP studies do not include trauma-exposed and non-trauma exposed controls and comorbidity is ignored.

Accordingly, research needs to examine P3 amplitude to neutral target stimuli in a PTSD group relative to non-trauma and trauma-exposed controls. It would be informative to compare patients with ASD and chronic PTSD to examine the effects of amount of exposure to ongoing trauma reminders. Finally, ERP studies need to examine the effects of comorbid disorders. The most prevalent comorbidity (up to 50%) in PTSD is major depression (Kessler et al., 1995). Although depression is associated with reduced P3 amplitude (Kemp et al., 2009), no ERP studies have examined the effect of comorbid depression on P3 amplitudes in PTSD.

This study examined the impact of PTSD status and the amount of trauma exposure on P300 amplitude by comparing participants with PTSD, ASD, trauma-exposed and non-trauma exposed controls. Secondly, to examine the effect of comorbid depression, analyses were repeated removing PTSD participants with comorbid depression. Finally, skin conductance (reflecting orienting) was recorded concurrently with P300.