A new study shines a light on the role of spindles in alleviating anxiety in PTSD as well as confirms their established role in the transfer of new information to longer-term memory storage.
“These findings may be meaningful not only for people with PTSD, but possibly for those with anxiety disorders,” said senior author Anne Richards, MD. “There are non-invasive ways that might harness the benefits of this sleep stage to provide relief from symptoms,” she said.
The researchers enrolled 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 researchers studied the spindles during non-rapid eye movement 2 (NREM2) sleep, the phase of sleep when they mainly occur, which comprises about 50% of total sleep.
In the study, participants attended a “stress visit” in which they were shown images of violent scenes, prior to 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. “This provides compelling evidence that stress was a contributing factor in spindle-specific sleep rhythm changes,” said first author Nikhilesh Natraj, PhD. Notably, in participants with greater PTSD symptoms, the increased spindle frequency after stress exposure reduced anxiety post-nap.
The naps in the study took place shortly after exposure to violent images. The researchers think it is likely that sleep occurring days or weeks after trauma will have the same therapeutic effect , and point to interventions that could trigger the spindles associated with NREM2 sleep and benefit patients with stress and anxiety disorders.
“In lieu of such inventions, sleep hygiene is definitely a zero-cost and easy way to ensure we are entering sleep phases in an appropriate fashion, thereby maximizing the benefit of spindles in the immediate aftermath of a stressful episode,” he said.
Nikhilesh Natraj, Thomas C. Neylan, Leslie M. Yack, Thomas J. Metzler, Steven H. Woodward, Samantha Q. Hubachek, Cassandra Dukes, Nikhila S. Udupa, Daniel H. Mathalon, Anne Richards. Sleep Spindles Favor Emotion Regulation Over Memory Consolidation of Stressors in Posttraumatic Stress Disorder. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 2023; DOI: 10.1016/j.bpsc.2023.02.007
University of California – San Francisco. “Sleep phase can reduce anxiety in people with PTSD.” ScienceDaily. ScienceDaily, 3 May 2023. <www.sciencedaily.com/releases/2023/05/230503085340.htm>.
Photo by Taylor Deas-Melesh