From time to time, our conscious mind is invaded by unpleasant memories, often triggered by small occurrences in our surroundings. Typically, we can push these memories aside quickly, reducing the likelihood of future intrusions.

However, individuals suffering from depression, anxiety, or post-traumatic stress disorder (PTSD) often spend more time trapped in cycles of intrusive thinking, reinforcing negative rumination. Given that people with mental health issues frequently experience sleep disturbances — and that sleep is known to play a crucial role in memory processing — this connection has sparked scientific interest.

Previous research established a link between sleep deprivation and intrusive memories, but the underlying neurological mechanisms remained unclear. Scientists from the Department of Psychology at the University of York, United Kingdom, aimed to uncover how sleep deprivation leads to intrusive thoughts. Their findings were recently published in Proceedings of the National Academy of Sciences (PNAS).

The Suppression of Memories

The research team hypothesized that sleep deprivation disrupts the prefrontal cortex — a brain region responsible for functions such as memory processing and emotional regulation — leading to an increase in intrusive memories.

To test their theory, they divided over 80 participants into two groups: one group was deprived of sleep overnight, while the other group had a full night of restful sleep. Before the night began, participants were shown 48 face-scene pairs, with the scenes being either emotionally negative or neutral.

The next day, participants viewed reminder cues (faces) associated with these scenes while their brain activity was monitored using functional neuroimaging techniques (MRI). They either retrieved the scene or suppressed it and then reported if the scene came to mind, identifying failed suppression attempts as intrusions.

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REM Sleep and Memory Processing

The results revealed that sleep deprivation interferes with the prefrontal cortex’s ability to suppress memory retrieval, and the overnight restoration of this inhibitory function is linked to time spent in rapid eye movement (REM) sleep — confirming the researchers’ hypothesis and shedding light on the mechanisms behind memory suppression.

Previous studies have suggested that REM sleep — the stage associated with vivid dreaming — plays a key role in reducing the brain’s emotional reactivity the following day by engaging the prefrontal cortex.

Furthermore, people with psychiatric conditions who struggle to suppress intrusive thoughts often exhibit abnormalities in REM sleep. This suggests that sleep deprivation not only makes it harder to block unwanted memories but also impairs the brain’s ability to regulate spontaneous thoughts.

Implications for Understanding Mental Disorders

Alongside nutrition and exercise, sleep is a cornerstone of a healthy lifestyle — particularly when it comes to mental health. This recognition has led to increased public interest in maintaining good sleep hygiene and scientific efforts to understand the relationship between sleep and emotional regulation.

Since memories significantly shape how we perceive and respond to the world around us, failures in memory control may help explain the connection between sleep deprivation and emotional dysregulation.

“The findings add to a growing literature on the impacts of sleep deprivation on prefrontal control and underscore the importance of such findings for our understanding of mental health conditions that co-occur with chronic sleep disturbances,” the study authors concluded in the study.

Additionally, a deeper understanding of the cognitive and neural mechanisms connecting poor sleep to mental illness may aid in the development of new treatment and prevention strategies.

More specifically, both past research and the current study suggest that REM sleep plays a crucial role in restoring the prefrontal cortex’s ability to regulate memory and emotions.

In summary, these findings emphasize the essential role of sleep in maintaining control over memories and ongoing thoughts, reinforcing the value of promoting a culture that supports healthy sleep habits.

Read More: 6 Ways To Wake Up Feeling More Rested

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

Having worked as a biomedical research assistant in labs across three countries, Jenny excels at translating complex scientific concepts – ranging from medical breakthroughs and pharmacological discoveries to the latest in nutrition – into engaging, accessible content. Her interests extend to topics such as human evolution, psychology, and quirky animal stories. When she’s not immersed in a popular science book, you’ll find her catching waves or cruising around Vancouver Island on her longboard.