Anxiety moderates the effect of sleep on selective forgetting

While anxiety predisposes to distressing memories, the role of sleep in maintaining or attenuating unwanted memories has been understudied. This study aims to fill this knowledge gap by examining sleep-driven selective memory consolidation using a directed forgetting (DF) paradigm. DF refers to the intentional suppression of certain memories during encoding, and it is usually observed in both anxious and non-anxious individuals during wakefulness. While sleep potentially enhances DF, it is unclear how anxiety interacts with sleep. The sample (N = 58) was divided into low- and high-anxiety subgroups based on self-reported symptoms (GAD-7). The participants encoded to memory 120 face images (neutral/fearful). According to item-method DF, each image was instantly followed by Remember (R) or Forget (F) cue. Memory retrievals took place immediately, after a daytime nap in the sleep laboratory, and after two days. DF effect denoted the difference between R-cued and F-cued image recognition success. Overall, relative to F-cued, R-cued images were better recognized. This DF effect was moderated by anxiety and sleep: in low-anxiety individuals only, the magnitude of the DF effect increased significantly over the nap. This increase was associated with sleep spindle density. Event-related potential amplitudes at encoding associated with the DF effect at the immediate retrieval, but not at the later assessments. Sleep-related memory processing may be altered in individuals with elevated anxiety, making it harder to differentiate important from irrelevant information. This mechanism may contribute to the persistence of unwanted memories in anxiety. Understanding how sleep interacts with anxiety can open novel intervention possibilities.