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Randomized Controlled Trial
, 39 (12), 2125-2132

Effects of Sleep After Experimental Trauma on Intrusive Emotional Memories

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Randomized Controlled Trial

Effects of Sleep After Experimental Trauma on Intrusive Emotional Memories

Birgit Kleim et al. Sleep.

Abstract

Study objectives: To investigate sleep's effect in the immediate aftermath of experiencing an analog trauma in the laboratory on reducing intrusive emotional memory formation.

Methods: Sixty-five healthy women were exposed to an experimental laboratory trauma. They viewed a neutral and a trauma film in the laboratory and were randomly allocated to either a group that slept following film viewing or a group that remained awake. Sleep was recorded with electroencephalogram in a subgroup of participants in the sleep group. All participants recorded intrusive memories in the week following the film.

Results: The sleep group experienced fewer and less distressing intrusive trauma memories compared to the wake group. These effects were particularly evident toward the end of the week. Duration spent in stage N2 as opposed to light N1 sleep, a higher number of fast parietal sleep spindles and a lower rapid eye movement sleep density predicted intrusion frequency.

Conclusions: Our results have clinical implications and set the ground for early-intervention sleep studies following trauma and prevention of chronic posttrauma disorders.

Keywords: PTSD; emotional memory; intrusion; memory consolidation; sleep; trauma.

Figures

Figure 1
Figure 1
Effects of sleep on intrusive memory frequency. Following exposure to a trauma movie and a neutral movie, participants either slept or remained awake and then recorded intrusive memories of either movie during the following 6 days in an intrusion diary (a). Participants who slept report fewer intrusive trauma, but not neutral memories compared to those who remained awake (b). Moreover, intrusive trauma memories were less distressing in those who slept compared to those who remained awake, whereas no differences were found for neutral memories (c).
Figure 2
Figure 2
Associations between frequency of trauma film intrusions and sleep parameters. More stage 2 sleep (a) and a higher density of parietal fast sleep spindles (13–15 Hz) (b) were related to fewer trauma film intrusions. In contrast, increased time spent in stage 1 sleep (c) and increased rapid eye movement (REM) density (d) was related to more frequent intrusive reexperiencing.
Figure 3
Figure 3
Day-by-day profile of intrusive memories depicting mean number of intrusive memories on days 1 to 7 (a), and mean distress of intrusive memories (range 0–10) (b), including standard errors of the mean (SEM). The sleep group experienced significantly fewer intrusive memories (days 3, 6, and 7), but not during the first 2-day period, indicating possible initiation of a process of memory reconsolidation that continues over several nights. Intrusive memories were also significantly less affectively charged for days 3, 4, 6, and 7.

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