Q&A with psychology professor Jessica Payne: Sleep is critical for processing emotions and shoring up memory
"If you wake up before you head into REM sleep, and there’s a little bit too much stress or too much cortisol (a primary stress hormone) in your system, then you might find yourself awake, anxious and ruminating the rest of the night," said Payne. "And sleep deprivation itself is a stressor. When you’re sleep deprived, you produce more cortisol, which then makes it harder to sleep — it becomes a vicious cycle."