Where is the emotional Stroop effect in depression?

A multitude of studies have employed the emotional Stroop task, and its emotional Stroop effect (ESE), to find the attentional bias proposed to be one of the main factors in Beck’s Cognitive Theory of depression (1967; 1976). Nevertheless, the literature has remained inconsistent. This study aimed to investigate alternative accounts for both the ESE and depression. Fourteen participants were measured on depression severity and their response times to classifying the colour of positive, negative and neutral words compared across two tasks: the emotional Stroop task, where they were asked to ignore the word content, and a novel forced-processing task, where participants were required to process the content of each emotional word. There was a significant difference between when participants were required and not required to process emotion, suggesting that emotional processing is voluntary on the emotional Stroop task, and thus challenging the use of the task to investigate an automatic process such as attention. Rather than a specific negative bias, emotional interference was found from both positive and negative stimuli, and thus the ESE was identified as the difference between emotional and neutral conditions. The ESE was also deconstructed into the fast effect, interference from the current emotional word, and the slow effect, interference from the previously presented emotional word. Although the fast effect is typically used in the literature to identify an automatic attentional bias, it was the slow effect that was significantly related to depression severity in this study. With the support of other studies, a bias in depression is suggested to occur in a later disengagement stage of attentional processing rather than during the initial shifting of attention that is assumed in the fast effect. An inability to disengage from interfering emotional information is linked to rumination and a difficulty in regulating emotion in depression. The findings suggest the importance of focusing treatment on strategies to disengage from unhelpful emotional information, and have implications for how the ESE is used in research on depression.