Sleep and intrusive memories immediately after a traumatic event in emergency department patients

Abstract

Study objectives: Intrusive memories of psychological trauma are a core clinical feature of posttraumatic stress disorder (PTSD), and in the early period post-trauma may be a potential target for early intervention. Disrupted sleep in the weeks post-trauma is associated with later PTSD. The impact of sleep and intrusive memories immediately post-trauma, and their relation to later PTSD, is unknown. This study assessed the relationship between sleep duration on the first night following a real-life traumatic event and intrusive memories in the subsequent week, and how these might relate to PTSD symptoms at 2 months.

Methods: Patients (n = 87) recruited in the emergency department completed a sleep and intrusive memory diary from the day of their trauma and for the subsequent week, with optional actigraphy. PTSD, anxiety, and depression symptoms were assessed at 1 week and 2 months.

Results: A U-shaped relationship was observed between sleep duration on the first night and intrusive memories over the subsequent week: sleeping "too little" or "too much" was associated with more intrusive memories. Individuals who met Clinician-Administered PTSD Scale (CAPS) criteria for PTSD at 2 months had three times more intrusive memories in the first week immediately post-trauma than those who did not (M = 28.20 vs 9.96). Post hoc analysis showed that the absence of intrusive memories in the first week post-trauma was only observed in those who did not meet CAPS criteria for PTSD at 2 months.

Conclusions: Monitoring intrusive memories and sleep in the first week post-trauma, using a simple diary, may help identify individuals more vulnerable to later psychopathology.

Keywords: intrusive memories; mental imagery; posttraumatic stress disorder; single symptom; sleep; trauma.

Figure 1.

Frequency scattergraph showing the time course of the number of intrusive memories per day for the first week after the day of the traumatic event (day 2 to day 8). The size of the circles represents the number of participants who reported the indicated number of intrusive memories on that particular day. The solid line shows the fit of a mixture model to summarize the number of intrusive memories through the 7-day period.

Figure 2.

Scattergraphs showing the relationship between (A) sleep duration on the first night after the traumatic event (sleep diary) and the total number of intrusive memories in the subsequent week (day 2 to day 8), and (B) change in sleep duration from before the trauma to the first night after the trauma and the total number of intrusive memories in the subsequent week (day 2 to day 8). The lines show significant positive quadratic relationships, indicating that (A) a “shorter” and “longer” sleep duration was associated with more intrusive memories than an intermediate sleep duration, and (B) a “decrease” and “increase” in sleep duration was associated with more intrusive memories than no change in sleep duration from before the traumatic event. Participants who met CAPS criteria for PTSD at 2 months are marked in red.