Physiological Effects of Suppression of Neutral and Traumatic Thoughts in Posttraumatic Stress Disorder
Type of DegreeDissertation
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Posttraumatic Stress Disorder (PTSD) is characterized by oscillation of cognitive intrusions and avoidance. Recent research findings suggest that thought suppression may lead to increased intrusive thoughts for trauma survivors, paradoxically increasing symptoms. Although the psychological effects of suppression have been studied, the possible physiological effects have yet to be investigated. Participants with trauma history, 25 with PTSD symptoms and 22 without symptoms (no-PTSD) engaged in a neutral white bear and trauma suppression task. A ten-minute adaptation period was observed in order to achieve accurate baseline recordings of galvanic skin response (GSR), heart rate (HR), and respiration. During session one, participants completed the neutral suppression task consisting of three phases, baseline, suppression, and expression. Participants returned to the lab one week later for session two, the trauma-related suppression task. During all phases of both tasks measures of GSR, HR, and respiration were collected. After each phase of both suppression tasks participants completed measures of thought control difficulty, subjective distress, and mood. Additionally, a baseline measure of salivary cortisol was collected at the beginning of session one, and a post-task saliva collection occurred five minutes after each expression phase. The primary goals of the current study were to: (1) examine Sympathetic Nervous System (SNS) physiological effects of suppression of trauma and neutral targets between groups with and without PTSD; (2) examine Central Nervous System (CNS) response to suppression of trauma and neutral targets between groups via salivary cortisol collection; and (3) replicate the post-suppression rebound effect found for trauma thought targets, but not neutral targets, within the PTSD group only. Patterns of target thought data revealed a post-suppression rebound effect for the no-PTSD group and the PTSD group for the neutral and trauma tasks, respectively. This data suggests that it is the content of target thoughts rather than suppression ability that leads to intrusions for those with PTSD. Suppression of neutral and trauma targets resulted in physiological reactivity; however each response system showed distinct patterns. No phasic cortisol group differences were found, although the no-PTSD group had somewhat higher post-neutral cortisol levels in comparison to the PTSD group. Overall, it appears that suppression is an effortful form of mental control that is taxing physiologically and mentally.