Subliminal processing of threat cues in posttraumatic stress disorder?

Vietnam combat veterans with and without posttraumatic stress disorder (PTSD) performed a computerized Stroop color-naming task involving supraliminal and subliminal (masked 57 ms presentations) of trauma words (e.g., medevac), positive words (e.g., celebrate), neutral household-item words (e.g., microwave), and color words (e.g., red in blue letters). Immediately thereafter, subjects performed a card Stroop involving similar word types. Although healthy combat veterans exhibited a standard Stroop interference effect for subliminal as well as for supraliminal color words, there was no persuasive evidence of enhanced interference for subliminal trauma words in the PTSD group. PTSD subjects exhibited enhanced interference for supraliminal trauma words early in the experiment, but this effect waned, thus suggesting habituation to the semantic content of threat cues. Interference for trauma material in the PTSD group appeared much more robust in the card version than in the single-item computerized version. Although trauma-specific interference effects in PTSD may be automatic in the sense of being involuntary, they do not appear automatic in the sense of occurring outside of awareness.