Sleep Spindles Play a Role in Soothing PTSD Anxiety and Enhancing Memory Retention

Summary: Brief bursts of brain activity during sleep known as sleep spindles could potentially help regulate anxiety in people with post-traumatic stress disorder (PTSD). Researchers believe that the study’s findings may be useful for people with anxiety disorders and are looking at non-invasive ways to harness the benefits of this sleep stage to relieve symptoms.

The study also suggests that sleep hygiene, electrical brain stimulation, or prescription sleep medications could promote the sleep spindles associated with non-rapid eye movement 2 (NREM2) sleep and potentially benefit patients with stress and anxiety disorders.

Key Facts:

Sleep spindles, brief bursts of brain activity during sleep, could potentially help regulate anxiety in people with post-traumatic stress disorder (PTSD).
The study involved 45 participants who had all experienced trauma, with about half having moderate symptoms of PTSD, and half having milder symptoms or no symptoms at all.
The research found that spindle frequency was higher during the “stress visit” than the control visit and that stress was a contributing factor in spindle-specific sleep rhythm changes.

Source: UCSF

A new study shows that sleep spindles, brief bursts of brain activity occurring during one phase of sleep and captured by EEG, may regulate anxiety in people with post-traumatic stress disorder (PTSD).

The 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. The findings challenge recent work by other researchers that has indicated spindles may heighten intrusive and violent thoughts in people with PTSD.

The final draft of the preprint publishes in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging on May 3, 2023.

“These findings may be meaningful not only for people with PTSD, but possibly for those with anxiety disorders,” said senior author Anne Richards, MD, MPH, of the UCSF Department of Psychiatry and Behavioral Sciences, the Weill Institute for Neurosciences and the San Francisco VA Medical Center.

“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.

Violent Images Used to Test Brain Processing

In the study, participants attended a “stress visit” in which they were shown images of violent scenes, such as accidents, war violence, and human and animal injury or mutilation, 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, of the UCSF Department of Neurology, the Weill Institute for Neurosciences and the San Francisco VA Medical Center.

Notably, in participants with greater PTSD symptoms, the increased spindle frequency after stress exposure reduced anxiety post-nap.

Sleeping Meds, Electrical Stimulation May Promote Sleep Spindles

The naps in tthe 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 think this is likely, and point to interventions that could trigger the spindles associated with NREM2 sleep and benefit patients with stress and anxiety disorders.

Prescription drugs, like Ambien, are one option that should be studied further, “but a big question is whether the spindles induced by medications can also bring about the full set of brain processes associated with naturally occurring spindles,” said Richards.

Electrical brain stimulation is another area for more study, researchers said. “Transcranial electrical stimulation in which small currents are passed through the scalp to boost spindle rhythms or so-called targeted memory reactivation, which involves a cue, like an odor or sound used during an experimental session and replayed during sleep may also induce spindles,” said Natraj.

“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.

The researchers’ next project is to study the role of spindles in the consolidation and replay of intrusive and violent memories many weeks after trauma exposure.

Co-authors: Thomas C. Neylan, MD, and Daniel H. Mathalon, PhD, MD, of the San Francisco VA Medical Center and UCSF; Leslie M. Yack, Thomas J. Metzler, Samantha Q. Hubachek, Cassandra Dukes, and Nikhila S. Udupa of UCSF; and Steven H. Woodward, PhD, of the Palo Alto VA Medical Center.

Funding: Anne Richards, MD, MPH, received a VA Career Development Award by the U.S. Department of Veterans Affairs (5IK2CX000871-05).

Abstract

Sleep Spindles Favor Emotion Regulation Over Memory Consolidation of Stressors in Posttraumatic Stress Disorder

Background

Posttraumatic stress disorder (PTSD) is a trauma-induced condition, characterized by intrusive memories and trauma-associated anxiety. Non–rapid eye movement (NREM) sleep spindles might play a crucial role in learning and consolidating declarative stressor information. However, sleep and possibly sleep spindles are also known to regulate anxiety, suggestive of a dual role for sleep spindles in the processing of stressors. Specifically, in individuals with high PTSD symptom burden, spindles might fail to regulate anxiety levels after exposure and instead might maladaptively consolidate stressor information.

Methods

To disentangle the role of spindles in declarative memory versus anxiety regulation after stressor exposure and to examine the role of PTSD in these processes, we measured nap sleep after a cohort of 45 trauma-exposed participants were exposed to laboratory stress. Participants (high vs. low PTSD symptoms) completed 2 visits: a stress visit involving exposure to negatively valent images before nap and a control visit. In both visits, sleep was monitored via electroencephalography. A stressor recall session occurred after the nap in the stress visit.

Results

Stage 2 NREM (NREM2) spindle rates were higher in stress versus control sleep, indicative of stress-induced changes in spindles. In participants with high PTSD symptoms, NREM2 spindle rates in stress sleep predicted poorer recall accuracy of stressor images relative to participants with low PTSD symptoms, while correlating with greater reduction in stressor-induced anxiety levels after sleep.

Conclusions

Contrary to our expectations, although spindles are known to play a role in declarative memory processes, our findings highlight an important role for spindles in sleep-dependent anxiety regulation in PTSD.