Specific phase of sleep to best calm an anxious brain identified
A fascinating new study from scientists at UC Berkeley has homed in on exactly which phase of sleep seems to best keep anxiety levels in check. The research both affirms a causal association between sleep and anxiety, and suggests sleep deprivation lowers activity in the prefrontal cortex, an area of the brain that helps regulate our emotions.
For well over a century scientists have observed a correlation between sleep disruption and mood disorders such as anxiety and depression. Only in the last few years have clear neural mechanisms been discovered helping us understand exactly what our brains are doing when we are asleep, and how physiologically disruptive sleep deprivation can be.
A new study from UC Berkeley has focused more specifically on how sleep can modulate a person’s anxiety levels. Using a number of experimental measures, including polysomnography and functional MRI, the research first found that just one night of sleep deprivation resulted in 50 percent of the study subjects reporting anxiety levels the next day equal to those detected in subjects with clinically diagnosed anxiety disorders.
Imaging the subjects’ brains when watching emotionally-triggering videos revealed sleep deprivation causes a reduction in prefrontal cortex (PFC) activity. The lower the PFC activity, the higher a person’s anxiety levels.
And even more impressively, the researchers managed to specifically home in on the phase of sleep that seems to correlate with better PFC activity the next day. A phase of sleep known as NREM (non rapid eye movement) slow-wave sleep could be directly linked with better subsequent PFC activity and reductions in anxiety.
"We have identified a new function of deep sleep, one that decreases anxiety overnight by reorganizing connections in the brain," explains Matthew Walker, senior author on the new study. "Deep sleep seems to be a natural anxiolytic (anxiety inhibitor), so long as we get it each and every night."
The research was able to draw a direct line between how much slow-wave sleep a subject completed overnight and their anxiety levels the next day. A larger online survey of 280 subjects revealed small night-to-night changes in sleep quality directly correlated with day-to-day changes in anxiety levels.
"People with anxiety disorders routinely report having disturbed sleep, but rarely is sleep improvement considered as a clinical recommendation for lowering anxiety," says Eti Ben Simon, lead author on the study. "Our study not only establishes a causal connection between sleep and anxiety, but it identifies the kind of deep NREM sleep we need to calm the overanxious brain."
Other recent research has affirmed the importance of this particular phase of deep sleep, suggesting it is during this specific cycle that the brain seems to wash itself of the toxic proteins often associated with dementia and Alzheimer’s disease.
Walker also intriguingly hypothesizes a link between an increase in anxiety disorders seen in modern industrialized nations and shorter, more disrupted sleep patterns caused by modern lifestyles.
"... the findings suggest that the decimation of sleep throughout most industrialized nations and the marked escalation in anxiety disorders in these same countries is perhaps not coincidental, but causally related," concludes Walker. "The best bridge between despair and hope is a good night of sleep."
The new research was published in the journal Nature Human Behavior.
Source: UC Berkeley