Researchers have uncovered one of the strongest neural links between sleep and anxiety disorders. According to a new study, just one sleepless night can trigger a rise of up to 30% in anxiety levels. The good news is that the remedy is simple, all-natural, and free: deep slumber.

“We have identified a new function of deep sleep, one that decreases anxiety overnight by reorganizing connections in the brain,” said study senior author Matthew Walker, a University of California Berkeley professor of neuroscience and psychology. “Deep sleep seems to be a natural anxiolytic (anxiety inhibitor), so long as we get it each and every night.”

Walker and colleagues performed a series of experiments using functional MRI and polysomnography (a test conducted to study sleep and to diagnose a variety of sleep disorders), which scanned the brains of 18 young adults as they viewed emotionally stirring videos after a full night of sleep and, later, after a sleepless night.

After each session, the test subjects’ anxiety levels were measured using a standard questionnaire called the state-trait anxiety inventory.

When the subjects were sleep-deprived, brain scans showed a significant lowering of neural activity in the medial prefrontal cortex — which is involved in anxiety control — while the brain’s deeper emotional centers were overactive.

“Without sleep, it’s almost as if the brain is too heavy on the emotional accelerator pedal, without enough brake,” Walker said.

The researchers found that a full night’s sleep resulted in a marked decline in anxiety levels as measured by brain waves. This effect was especially pronounced in those who experienced slow-wave non-rapid eye movement (NREM), a sleeping state in which brain oscillations become highly synchronized, as well as heart rates and blood pressure drop.

These findings were replicated in a subsequent study involving another 30 participants, showing that those who got more sleep also experienced the lowest levels of anxiety during the next day.

“Deep sleep had restored the brain’s prefrontal mechanism that regulates our emotions, lowering emotional and physiological reactivity and preventing the escalation of anxiety,” Simon said.

According to the researchers, their results consistently show that even subtle changes in sleep quality can affect anxiety levels. This information may be very important considering there are 40 million Americans, both adults and children, who experience an anxiety disorder. It is perhaps no coincidence that the marked escalation of anxiety disorders in industrial countries has grown in sync with the decimation of sleep.

“People with anxiety disorders routinely report having disturbed sleep, but rarely is sleep improvement considered as a clinical recommendation for lowering anxiety,” Simon said. “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.”

The findings were reported in the journal Nature Human Behaviour.