Researchers at the University of California - San Francisco (UCSF) have found that sleep spindles, brief bursts of brain activity that occur during non-rapid eye movement 2 (NREM2) sleep, may regulate anxiety in people with post-traumatic stress disorder (PTSD). The study challenges the findings of previous research indicating that spindles may heighten intrusive and violent thoughts in people with PTSD. The new study sheds light on the role of spindles in alleviating anxiety in PTSD as well as in the transfer of new information to longer-term memory storage.
The researchers studied the spindles during NREM2 sleep, the phase of sleep when they mainly occur, in 45 participants who had all experienced combat or noncombat trauma. Approximately half had moderate symptoms of PTSD, and the other half had milder symptoms or were asymptomatic. The participants were shown images of violent scenes before a lab-monitored nap that took place about two hours later. Anxiety surveys were conducted immediately after exposure to the images, as well as after the nap when recall of the images was tested. The researchers also compared anxiety levels in the stress visit to those in a control visit without exposure to these images.
The researchers found that spindle rate frequency was higher during the stress visit than during the control visit, providing compelling evidence of stress contributing to spindle-specific sleep rhythm changes. Notably, in participants with greater PTSD symptoms, the increased spindle frequency after stress exposure reduced anxiety post-nap.
Senior author Anne Richards of the UCSF Department of Psychiatry and Behavioral Sciences said that the findings may be meaningful not only for people with PTSD but possibly for those with anxiety disorders. She added that there were non-invasive ways to harness the benefits of this sleep stage to provide relief from symptoms. The study is published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
The naps in the study took place shortly after exposure to violent images, raising a question about whether sleep occurring days or weeks after trauma will have the same therapeutic effect. The researchers believe that it is likely and point to interventions such as prescription drugs like Ambien and electrical brain stimulation that could trigger the spindles associated with NREM2 sleep and benefit patients with stress and anxiety disorders.
