Even modest reductions in sleep can trigger elevated anxiety the following day, according to new research published in Nature Human Behaviour. The findings suggest that sleep deprivation provokes anxiety symptoms by impairing activity in a brain region that is crucial for high level cognitive functions.

“Poor sleep and anxiety are intimately linked. When we are anxious our sleep is disturbed and when our sleep is disturbed we become anxious. It is a vicious cycle that we now know can start from poor sleep,” explained study author Eti Ben Simon, a neuroscientist and a sleep researcher at The Center for Human Sleep Science in UC Berkeley.

“People who suffer from poor sleep (such as insomnia) are twice as likely to develop an anxiety disorder relative to people who sleep well. We have plenty of evidence that not getting enough sleep can lead to anxiety but until now we didn’t know why. Specifically, we didn’t know what is it about sleep loss that triggers anxiety but also what is it about a good night of sleep that helps keep us calm.”

The researchers used functional magnetic resonance imaging (fMRI) to examine the brain activity of 18 participants as they viewed emotionally-charged video clips after a full night of sleep, and again after 24 hours of total sleep deprivation. Participants also rated their level of anxiety in the evenings and mornings.

After being awake for 24 hours, half of the participants reported levels of anxiety that exceeded the clinical threshold for anxiety disorders.

The researchers found that sleep deprivation was associated with reduced activity in the medial prefrontal cortex, an area of the brain linked to emotional control. This reduced activity in turn predicted an increase in anxiety. The researchers replicated these results in a study of another 30 participants.

Sleep deprivation was also associated with changes in the amygdala, dorsal anterior cingulate cortex, and insula — but these changes were not associated with anxiety levels.

“Our findings point to an immediate impact of sleep loss, as well as poor sleep, on anxiety levels the very next morning. That is, lack of sleep is a causal trigger that instigates anxiety, even after just one night,” Simon told PsyPost.

“When looking into brain activity, we found that sleep loss targets the same brain regions that make us susceptible to anxiety — regions that process and regulate emotional reactivity. When this region is taken offline, as is the case with a lack of sleep, our deep emotional centers are left uncontrolled and anxiety ensues.”

The researchers also found that after a full night of sleep, during which participants’ brain waves were measured via electrodes placed on their heads, the participants’ anxiety levels declined significantly. This was especially true for those who experienced more non-rapid eye movement (NREM) sleep.

“On a positive note, we have discovered that deep sleep, otherwise known as NREM slow wave sleep, can help restore activity in these prefrontal regions and help keep us calm the next day,” Simon said.

“We have discovered a new benefit of deep sleep, acting as a nightly and natural anxiolytic. That is, if general practitioners aim to treat the sleep complaints of individuals with anxiety using methods such as Cognitive Behavioral Therapy for Insomnia (CBT-I), it may provide significant clinical benefits and decrease the need for anti-anxiety medication.”

In addition to the lab experiments, the researchers conducted two online studies in which 480 participants reported their sleep quality and subjective anxiety levels across two or four consecutive nights and days. They found that variations in sleep quality were associated with day-to-day changes in anxiety.

“Our findings point to the importance of sufficient sleep in managing anxiety. When individuals start prioritizing their sleep and getting enough, deep sleep restores activity in regions that regulate emotions and help keep us calm. The next step is to pinpoint exactly how deep sleep enables such emotional reset,” Simon told PsyPost.

“One possible mechanism we discuss in the paper has to do with the ‘flight or fight’ response. The flight or fight response is part of the autonomic nervous system that helps us gear towards physical or emotional challenges by increasing heart rate and blood pressure for instance. If this response is chronically activated it can lead to greater levels of stress and anxiety.”

“Every night when we go into deep sleep this branch of the autonomic nervous system is virtually shut down allowing our brain and body to recover and de-stress. An important next step is to now connect this nightly benefit of deep sleep to the changes we see in anxiety and brain activity the next day,” Simon explained.

But the benefits of a good night’s sleep extend far beyond reducing anxiety.

“Deep sleep is one of the best natural forms of blood-pressure ‘medications’ you could ever wish for, lowing your heart rate each night. Deep sleep also helps you regulate your blood sugar, reducing your risk of diabetes, and also helps regulate your appetite hormones, preventing you from overeating. Finally, deep sleep also helps cleanse your brain of the toxic proteins linked to Alzheimer’s disease, and it also helps ‘hit the save button’ on new memories so you don’t forget,” Simon said.

“Simply put, getting sufficient sleep is the single most effective step we can take to help reset our brain and body every single night. Do your best to protect your sleep and it will protect you in return.”

The study, “Overanxious and underslept“, was authored by Eti Ben Simon, Aubrey Rossi, Allison G. Harvey, and Matthew P. Walker.