Explicit emotional memory biases in mood disorders: A systematic review

Research suggests that major depressive disorder (MDD) and bipolar disorder (BD) are both associated with unique emotional memory (EM) biases. To better elucidate the EM phenotypes of these disorders, we systematically reviewed the literature on non-autobiographical explicit EM biases in individuals with MDD and BD compared to healthy controls. The following databases were searched: Cochrane, Embase, HAPI, LILACs, Medline, PsycInfo and Web of Science. Grey literature and hand searches were also performed. Fourteen studies met full eligibility criteria. Eleven studies included data from an MDD sample (10 during acute depression, 1 during euthymia) and 3 studies included data from a BD sample (2 during acute mood episodes, 1 during euthymia). Only 3 of the studies in acute depression revealed a negative explicit EM bias. One study in MDD during euthymia revealed an EM deficit for negative stimuli. One of the two studies in BD (type I; BD-I) during an acute mood episode revealed a positive explicit EM bias, while the other showed no bias. One study in BD during euthymia showed an EM deficit for negative stimuli. Overall, this review concludes that current empirical evidence does not readily support the existence of an explicit EM bias in MDD during acute depression. The identification and implications of potential moderating factors on explicit EM performance in MDD and BD during both illness stages are discussed.