The National Center for Post-Traumatic Stress Disorder PTSD RESEARCH QUARTERLY

Clinicians have traditionally viewed cognition as equivalent to conscious thought, and accordingly have relied on questionnaires and structured inter­ views to study the cognitive aspects of emotional disorders. But limitations of introspective self-re­ port have prompted investigators to apply increas­ ingly the information-processing methods of ex­ perimental psychology in an effort to elucidate cog­ nitive pathology in disorders such as PTSD (e.g., Litz & Keane, 1989; McNally, 1993). These methods can isolate dysfunctions in attention and memory, and can supplement traditional self-report ap­ proaches to assessment. PTSD researchers have conducted two types of information-processing studies.Valence-independent studies require subjects to process information that varies in complexity, but not in emotional valence. Included under this rubric are experiments on intel­ ligence, short-term memory, and so forth (e.g., McNally & Shin, 1995; Yehuda et al., 1995). Valencedependent studies require subjects to process affectively charged information related to trauma. Included under this rubric are experiments on attentional and memory biases favoring processing of trauma-relevant information. This article reviews a bibliography of studies of valence-dependent pro­ cessing biases in PTSD. PTSD researchers have devised methods for as­ sessing intrusive cognition in the laboratory that do not require introspective self-report (McNally et al., 1990). One such method is the emotional Stroop (1935) color-naming paradigm. In this attentional paradigm, subjects are shown words of varying emotional significance that are printed in different colors. They are asked to name the colors in which the words appear while ignoring the meanings of the words. Delayed color-naming (i.e., Stroop inter­ ference) occurs when the meaning of a word cap­ tures the subject’s attention despite the subject’s effort to focus on its color. Because color-naming delays reflect involuntary activation of meaning, interference produced by trauma-related material may provide a quantitative index of intrusive cog­ nition. That is, PTSD patients ought to take longer to name the colors of words related to trauma relative to other words, whereas people without PTSD should not. To test the viability of this paradigm for capturing intrusive cognition, McNally et al. (1990) had Viet­ nam combat veterans with and without PTSD colorname words related to trauma (e.g., bodybags), words related to another anxiety disorder (obsessive-com­ pulsive disorder, e.g., germs), words having positive emotional valence (e.g., love), and words having neutral valence (e.g., input). Each word was printed in one of several colors and words of a certain type appeared on a single large card. The dependent measure was the time taken for the subject to name the colors of all the words on a single card. PTSD patients took significantly longer to color-name trauma words relative to other words and relative to healthy combat veterans who did not respond dif­ ferentially as a function of word type. Moreover, interference for trauma words was significantly re­ lated to severity of PTSD symptoms, but not to extent of combat exposure. These results suggest that Stroop interference for trauma-related words may reflect severity of intrusive cognition rather than just a history of exposure to traumatic events. Cassiday et al. (1992) provided further data con­ sistent with this interpretation of the trauma-spe­ cific Stroop effect. Studying rape victims with and without PTSD, they found that interference for words related to rape trauma was related to severity of intrusive symptoms, but not to severity of avoid­ ance and numbing symptoms. Thus, experimental (Stroop) and self-report indices of intrusion con­ verged. Stroop experiments have repeatedly shown that words closely related to trauma produce more inter­ ference than negative words less closely related to trauma. Using a computerized procedure that en­ abled them to select idiographic stimuli for each subject, Kaspi and colleagues (1995) found that pa­ tients with combat-related PTSD exhibited more interference for trauma words than for equally “nega­ tive” words that were unrelated to trauma. Also studying veterans with PTSD, Vrana and colleagues