Investigating the mediating effect of working memory on intentional forgetting in dysphoria

Our aim was to determine if deficits in intentional forgetting that are associated with depression and dysphoria (subclinical depression) could be explained by variations in working memory capacity. Sixty dysphoric and 61 non-dysphoric participants completed a modified version of the think/no-think (TNT) task and a measure of complex working memory (the operation span task). The TNT task involved participants learning a series of emotional cue-target word pairs. They were then presented with a series of the cues and asked to either recall the associated target or to prevent it from coming to mind (by thinking about a substitute word). Participants were subsequently asked to recall the targets to all cues (regardless of previous recall instructions). As expected, we found that dysphoric individuals exhibited impaired forgetting relative to the non-dysphoric participants. Also as expected, we found that greater working memory capacity was associated with more successful forgetting. Critically, we found that working memory capacity mediated the effect of depression on intentional forgetting. That is, depression influenced forgetting indirectly via its effect on working memory, perhaps reducing the amount of available working memory resources that could be applied to the suppression of the memories. These findings are important as they provide an additional explanation for the finding of impaired forgetting in depression and also suggest that working memory training might be a viable intervention for improving the ability of depressed individuals to prevent unwanted memories from coming to mind.