Inadequate sleep leads to changes in brain activity that are linked to anxiety.

In a laboratory study, Eti Ben Simon and Matthew Walker and their colleagues at the University of California, Berkeley, found that when healthy volunteers were kept awake for 24 hours, they had higher anxiety levels the next morning than they did after a full night’s sleep. In fact, when sleep-deprived, half of the study participants reported anxiety levels typically seen in people with clinical anxiety disorders. And online surveys completed by a larger number of volunteers showed that ordinary fluctuations in nightly sleep quality predict next-day anxiety levels.

The team also imaged the brains of the sleep-lab participants as they watched video clips designed to conjure up negative emotions. People who watched these videos after sleep deprivation showed less activity in the prefrontal cortex (PFC), an area involved in emotional control, than they did when they were well-rested. Those with the greatest drops in PFC activity reported the largest spikes in anxiety after an all-nighter.

More and higher-quality non-REM slow-wave sleep — often referred to as deep sleep — correlated with greater recovery of PFC activity and greater reductions in next-day anxiety.