Seeking the source of emotional Stroop interference effects in PTSD: a study of P3s to traumatic words.

We investigated the source of emotional Stroop interference effects in posttraumatic stress disorder (PTSD) by measuring reaction times and P3 latencies and amplitudes to personal traumatic, personal positive, and neutral words in a modified Stroop paradigm. Individuals with PTSD were slower to indicate word color, especially for traumatic words, thereby replicating emotional Stroop interference in PTSD. Individuals with PTSD also had significantly reduced and delayed P3 components across word types. Across diagnostic groups, frontal P3 amplitudes were larger to personal positive and traumatic words compared to standard neutral words. However, the absence of Diagnosis x Word Type interactions for P3 measures suggests that individuals with PTSD do not differ from individuals without PTSD in the encoding and recognition of the color of traumatic relative to nontraumatic words, and that Stroop interference does not occur during these early stages of processing.