“Sleep acts like an emotional soothing balm, resetting the appropriate reactivity in emotional centers of our brain,” says researcher Matt Walker, PhD, professor of psychology and neuroscience at University of California Berkeley. “Without sufficient sleep, emotional functions start to go awry, including a ramping up of anxiety.” How do they know? Dr. Walker and other researchers discovered that sleep deprivation intensifies activity in two regions of the brain responsible for managing anxiety and anticipation: the amygdala and the insula. In order to study the relationship between the two, researcher incited anticipatory anxiety by showing 18 healthy adults with diverse levels of anxiety (but without anxiety disorders) a set of visual cues prior to viewing a series of images. A yellow circle indicated a neutral image, a red minus sign meant the image would be disturbing, and a white question mark meant it could be either. The researchers studied the brain activity at each primer image and found that, when the participants were sleep deprived, they had remarkably higher activity in the amygdala and the insula than when they enjoyed a full night’s sleep. More from Prevention: 5 Signs You’re Sleep Deprived But if you’re already an anxious person, look out—the research also showed that those who already deal with anxiety issues are more vulnerable to the effects of missing their eight hours. Researchers aren’t quite sure why, but they’ve got some ideas. “It could be that their brain activity in these anxiety-related regions is already high, and sleep deprivation subsequently ratchets it up disproportionately as a consequence,” Dr. Walker suggests. More from Prevention: How Much Sleep Do You Really Need?