Sleep deprivation alters mood and memory, researcher explains

Lack of sleep doesn’t just leave you tired—it disrupts how your brain processes emotions and stores information, according to sleep researcher Birgitte Rahbek Kornum in an interview with Danish broadcaster DR.

The brain relies on sleep to strengthen neural connections, consolidating memories and clearing space for new learning. “Memory doesn’t function as well when we’ve slept poorly,” Kornum said. Sleep is critical both before learning—preparing the brain to absorb information—and afterward, when it helps lock in what’s been learned.

Emotional control also weakens without adequate rest. Studies show sleep helps regulate mood, making it easier to manage frustration and interpret others’ emotions. “You’re more likely to lose your temper,” Kornum noted, adding that sleep can even dull the emotional intensity of traumatic memories over time.

Hormone regulation is another key function. During sleep, the body releases growth hormone, adjusts stress hormone cortisol (which naturally rises toward morning to prepare for waking), and fine-tunes other hormonal cycles. “Sleep keeps the body’s hormonal balance in check,” Kornum explained.

The effects extend beyond fatigue: poor sleep can heighten irritability, impair judgment, and leave gaps in recall—consequences familiar to many, particularly parents of young children.