P3a amplitude to trauma-related stimuli reduced after successful trauma-focused PTSD treatment.

An elevated P3a amplitude to trauma-related stimuli is strongly associated with posttraumatic stress disorder (PTSD), yet little is known about whether this response to trauma-related stimuli is affected by treatment that decreases PTSD symptoms. As an analysis of secondary outcome measures from a randomized controlled trial, we investigated the latency and amplitude changes of the P3a in responses in a three-condition oddball visual task that included trauma-related (combat scenes) and trauma-unrelated (threatening animals) distractors. Fifty-five U.S. veterans diagnosed with combat-related PTSD were randomized to receive either active or sham repetitive transcranial magnetic stimulation (rTMS). All received cognitive processing therapy, CPT+A, which requires a written account of the index trauma. They were tested before and 6 months after protocol completion. P3a amplitude and response time decreases were driven largely by the changes in the responses to the trauma-related stimuli, and this decrease correlated to the decrease in PTSD symptoms. The amplitude changes were greater in those who received rTMS + CPT than in those who received sham rTMS + CPT, suggesting that rTMS plays beneficial role in reducing arousal and threat bias, which may allow for more effective engagement in trauma-focused PTSD treatment.