How was sleep on the first night after trauma linked to intrusive memories?

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

The researchers recruited 87 patients in an emergency department. Patients completed a sleep and intrusive memory diary from the day of their trauma through the subsequent week, with optional actigraphy. PTSD, anxiety, and depression symptoms were assessed at 1 week and 2 months.

A U-shaped relationship emerged: sleeping too little or too much on the first night was associated with more intrusive memories over the following week. People who met the Clinician-Administered PTSD Scale (CAPS) criteria for PTSD at 2 months had three times more intrusive memories in the first week after trauma than those who did not, with means of 28.20 versus 9.96. A post hoc analysis found that having no intrusive memories in the first week after trauma was observed only among people who did not meet CAPS criteria for PTSD at 2 months.

The researchers concluded that monitoring intrusive memories and sleep during the first week after trauma using a simple diary may help identify people more vulnerable to later psychopathology.