Summary: During REM sleep the brain’s locus coeruleus reduces or stops releasing noradrenaline, which helps decouple the emotional charge from memories. When this REM-related process is interrupted—common in restless or fragmented sleep—memories can remain emotionally powerful, contributing to rumination and symptoms similar to PTSD. For people who sleep well, emotional intensity linked to embarrassing or distressing memories often diminishes by morning.
Source: CORDIS
Why do certain memories keep us awake at night? Sleep researcher Eus van Someren explains how REM sleep, emotional processing, and insomnia intersect.
Many people awaken replaying a mortifying moment or worrying about a past conversation. There is experimental evidence for this “nocturnal cringe” effect. Van Someren and colleagues showed that people who are good sleepers typically experience less emotional intensity about an embarrassing event the next morning than they did the previous evening, as measured by brain imaging of limbic activity.
In one memorable experiment, volunteers were asked to sing slowly—karaoke style—to familiar songs such as “Silent Night,” but they could not hear their own voices while recording. Later, researchers played the recordings back to the participants and measured their physiological responses (for example, blushing and other markers of autonomic arousal) and collected self-reported embarrassment ratings. On average, the emotional impact of the embarrassment was reduced after a night of normal sleep.
How does REM sleep help regulate emotions?
A key insight from van Someren’s work is that REM sleep appears to play a specific role in separating the factual content of a memory from its emotional charge. During REM, the brain’s locus coeruleus—an area that releases the neurotransmitter noradrenaline (also called norepinephrine), which is closely linked to stress and alertness—reduces its activity. With less noradrenaline signaling to the amygdala and related emotional circuits, the brain can reprocess memories without recreating a strong stress response.
When this REM-related downregulation of noradrenaline happens, the association between a memory and its immediate emotional response can weaken. That is why someone may feel less embarrassed, anxious, or upset about a past incident after a good night’s REM sleep.
By contrast, people who experience restless or fragmented sleep miss out on this restorative REM function. Restless sleep can mean the sleeper repeatedly shifts back toward wakefulness or cycles through lighter sleep stages, limiting sustained REM periods. Without that REM benefit, emotional memories may remain highly charged—this pattern is prominent in conditions such as post-traumatic stress disorder (PTSD), and poor sleepers generally show a higher vulnerability to persistent negative emotional states.
Insomnia risk has both genetic and environmental components. Genetic variants associated with insomnia overlap with those linked to depression and anxiety, and early life adversity increases the likelihood that restless sleep patterns will develop. In long-term follow-up work, van Someren reported that when insomnia is left untreated, a substantial portion of sufferers progress to depression; in one study 43% of untreated insomniacs developed depression compared with 16% among those who received appropriate intervention.
What can be done to protect emotional health through better sleep?
Although general sleep hygiene—such as avoiding screens close to bedtime—remains useful, van Someren emphasizes that specific treatments are needed for restless sleep and chronic insomnia. Cognitive behavioral therapy for insomnia (CBT-I) is the most well-supported non-drug intervention and is used to limit the harm caused by fragmented sleep. One targeted approach within CBT-I is sleep consolidation or sleep restriction: temporarily reducing total time in bed can help re-align sleep architecture and encourage more efficient sleep, concentrating REM and deep sleep into a stable nightly window.
Van Someren also highlights a gap in sleep research: most studies linking sleep to memory and learning focus on facts and skills rather than on emotions and physiological distress, even though these domains are closely interconnected. Better understanding how sleep stages like REM influence the emotional processing of memories could lead to interventions that prevent rumination, reduce the risk of mood disorders, and improve overall mental health.
If you find yourself replaying an awkward moment in the dark, remember that a consolidated night of sleep—especially uninterrupted REM—often reduces the intensity of the emotional memory by morning. Seeking help for persistent sleep problems can protect both sleep quality and emotional resilience.
About this sleep and psychology research news
Author: Press Office
Source: CORDIS
Contact: Press Office – CORDIS
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