تاثیر استفاده از داروهای ضدافسردگی بر پردازش اطلاعات عاطفی در افسردگی عمده Effect of Antidepressant Medication Use on Emotional Information Processing in Major Depression

There is now substantial theoretical and empirical support for the importance of information processing biases in the maintenance, and perhaps the etiology, of major depression (1–۳). Specifically, biased attention to depression-relevant material and avoidance of positive information are hypothesized to maintain the disorder. Recent research has also demonstrated that modifying these biases reduces symptoms of depression (4–۶). According to a recent cognitive neuropsychological model of depression (7), antidepressant medications—particularly those that target serotonin and norepinephrine—may act by modifying emotional information processing. Modified emotional information processing, in turn, is thought to lead to downstream antidepressant effects. This model helps explain why antidepressant medication use is not immediately associated with amelioration of depressed mood. As Harmer and colleagues note (7), “Rather than acting as direct ‘mood enhancers,’ antidepressants may re-tune how we process personal and socially relevant affective information” (p. 107). This model follows from a series of studies suggesting that 1) antidepressants influence emotional information processing early in treatment; 2) changes in emotional information processing occur earlier than and in the absence of changes in subjective mood; and 3) early changes in information processing are associated with eventual therapeutic improvement (see the review by Harmer et al. [7]). Thus far, much of this research has been conducted with healthy subjects. For example, Browning et al. (8) randomly assigned 32 healthy volunteers to receive either one dose of citalopram or a placebo pill. Consistent with the cognitive neuropsychological hypothesis, individuals who received the antidepressant demonstrated greater attention to positive stimuli, as assessed with a visual probe task. More recently, researchers have begun to evaluate this phenomenon in individuals with depression. For instance, Harmer et al. (9) conducted a double-blind placebocontrolled study evaluating patients with depression and healthy subjects. In line with the cognitive neuropsychological model, depressed patients who received placebo exhibited lower recognition of positive facial expressions and lower memory for positive information, as well as slower speed to respond to positive personality adjectives, compared with healthy subjects. Notably, these information processing effects in the depressed patients were reversed with the administration of just a single dose of an antidepressant (reboxetine). However, there were not corresponding reductions in subjective ratings of mood or anxiety after this initial administration. In this study, we built on previous research to focus specifically on the relationship between antidepressant medication use and selective attention to emotional visual stimuli, using eye-tracking technology, in a sample of participants with major depressive disorder as well as a nondepressed comparison group. This research adds to the small number of studies that have empirically examined the cognitive neuropsychological model of depression in a clinical sample. The inclusion of a nondepressed comparison group is also valuable for comparative purposes insofar as it allows us to more clearly delineate “normal” attention for emotional information. Our use of an eye-tracking paradigm is particularly valuable because it allows for multiple dynamic measures of selective attention (10). This is critical because it enables us to capture the more elaborative stages of attention that are particularly relevant for patients with major depression (11). Eye tracking also specifically provides an assessment of overt attention, since eye movements are necessarily associated with shifts in attention, whereas the dot-probe task used in previous studies does not always elicit eye movements and may measure both overt and covert shifts in attention (12, 13). Ours is also the first study to examine the effects of antidepressant medication, as prescribed in the community, on emotional information processing. We used eye tracking to measure selective attention (total gaze duration, mean number of fixations, mean fixation duration) for dysphoric, threatening, positive, and neutral emotional scenes in a sample of community participants with major depression (both medicated and unmedicated) and a never-depressed comparison group. Consistent with previous work (8, 9), we hypothesized that antidepressant medication use, compared with nonuse, would be associated with greater selective attention for positive stimuli. We further predicted that there would not be significant group differences between the medicated major depression group and the nondepressed comparison group on selective attention for positive information, consistent with the idea that antidepressant medication use normalizes emotional information processing.