A natural, non-pharmaceutical remedy for anxiety disorders that affect 40 million Americans is as close as our beds, say University of California at Berkeley researchers. In Nature Human Behaviour, they reported that a sleepless night can trigger up to a 30 percent rise in anxiety levels, but a full night of slumber stabilizes emotions. The type most apt to calm and reset the anxious brain is deep sleep, also known as non-rapid eye movement, slow-wave sleep during which neural oscillations become highly synchronized and heart rate and blood pressure drop.

The researchers used brain scans to identify anxiety levels in 48 volunteers after nights of deep or restless sleep. “Without sleep, it’s almost as if the brain is too heavy on the emotional accelerator pedal without enough brake,” says the study’s senior author Matthew Walker, professor of neuroscience and psychology. A second survey of 280 people online found that the amount and quality of sleep people experienced from one night to the next predicted how anxious they would feel the next day. Even subtle nightly changes in sleep affected anxiety levels.