Restless rapid eye movement (REM) sleep impedes emotional processing, which may contribute to mood and anxiety disorders, new research suggests.

A team of Dutch investigators used fMRI to scan the brains of participants who underwent a stressful experience — in this case, hearing themselves sing out of tune. Brain activity was measured using electroencephalography (EEG).

The next morning, after spending the night in a sleep laboratory, participants were subjected to the same unpleasant experience. Those who had experienced REM sleep were less distressed, whereas those with restless REM sleep were once again upset.