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David Baxter PhD

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Neural link between sleep deprivation and psychiatric disorders found
October 24, 2007

Hyperactive emotional response in sleep-deprived people stems from a shutdown of the prefrontal lobe-a region that normally keeps emotions under control.

It has long been thought that sleep deprivation can play havoc with our emotions.

This is notably apparent in soldiers in combat zones, medical residents and even new parents. Scientists have known that sleep deprivation impairs a range of bodily functions, including the immune system and metabolism, as well as brain processes, such as learning and memory.

Yet, evidence for the role of sleep in governing our emotional brain state had remained surprisingly scarce.

Now new research from the University of California, Berkeley, and Harvard Medical School has found a neurological basis for the theory.

In the first neural investigation into what happens to the emotional brain without sleep, results from a brain imaging study suggest that while a good night's rest can regulate your mood and help you cope with the next day's emotional challenges, sleep deprivation does the opposite by excessively boosting the part of the brain most closely connected to depression, anxiety and other psychiatric disorders.

The team studied 26 healthy participants aged 18 to 30, breaking them into two groups of equal numbers of males and females. The sleep-deprived group stayed awake during day 1, night 1 and day 2, while the sleep-control group stayed awake both days and slept normally during the night. Brain scans using functioning Magnetic Resonance Imaging (fMRI) were performed at the end of day 2, during which each participant was shown 100 images that ranged from neutral to very negative. Using this emotional gradient, the researchers were able to compare the increase in brain response to the increasingly negative pictures.

The fMRI scans show that the amygdala, which is also a key to processing emotions, became hyperactive in response to negative visual stimuli - gory images - in study participants who stayed awake for 35 hours straight. Conversely, brain scans of those who got a full night's sleep in their own beds showed normal activity in the amygdala.

"It's almost as though, without sleep, the brain had reverted back to more primitive patterns of activity, in that it was unable to put emotional experiences into context and produce controlled, appropriate responses," said Matthew Walker, director of UC Berkeley's Sleep and Neuroimaging Laboratory and senior author of the study, published Oct. 22 in the journal Current Biology.

"Emotionally, you're not on a level playing field," Walker added.

That's because the amygdala, the region of the brain that alerts the body to protect itself in times of danger, goes into overdrive on no sleep, according to the study. This consequently shuts down the prefrontal cortex, which commands logical reasoning, and thus prevents the release of chemicals needed to calm down the fight-or-flight reflex.


If, for example, the amygdala reacts strongly to a violent movie, the prefrontal cortex normally lets the brain know the scene is make-believe and to settle down. But instead of connecting to the prefrontal cortex, the brain on no sleep connects to the locus coeruleus, the oldest, primitive part of the brain which releases noradrenaline (norepinephrine) to alert the body of imminent threats to survival, creating a volatile emotional mix.

The study's findings lay the groundwork for further investigation into the relationship between sleep and psychiatric illnesses. Clinical evidence has shown that some form of sleep disruption is present in almost all psychiatric disorders.

"This is the first set of experiments that demonstrate that even healthy people's brains mimic certain pathological psychiatric patterns when deprived of sleep," Walker said. "Before, it was difficult to separate out the effect of sleep versus the disease itself. Now we're closer to being able to look into whether the person has a psychiatric disease or a sleep disorder."

"We had predicted a potential increase in the emotional reaction from the brain [in people deprived of sleep], but the size of the increase truly surprised us," Walker said of the study's findings. "The emotional centers of the brain were over 60% more reactive under conditions of sleep deprivation than in subjects who had obtained a normal night of sleep."

"This adds to the critical list of sleep's benefits," Walker continued. "Sleep appears to restore our emotional brain circuits, and in doing so prepares us for the next day's challenges and social interactions. Most importantly, this study demonstrates the dangers of not sleeping enough. Sleep deprivation fractures the brain mechanisms that regulate key aspects of our mental health. The bottom line is that sleep is not a luxury that we can optionally choose to take whenever we like. It is a biological necessity, and without it, there is only so far the band will stretch before it snaps, with both cognitive and emotional consequences."

Since 1998, Walker, an assistant professor of psychology at UC Berkeley and a former sleep researcher at Harvard Medical School, has been studying sleep's impact on memory, learning and brain plasticity. During his research, he was struck with the consistency of how graduate students in his studies would turn from affable, rational beings into what he called "emotional JELL-O" after a night without sleep. He and his assistants searched for research that would explain the effect of sleep deprivation on the emotional brain and found none, although there is countless anecdotal evidence that lack of sleep causes emotional swings.

"You can see it in the reaction of a military combatant soldier dealing with a civilian, a tired mother to a meddlesome toddler, the medical resident to a pushy patient. It's these everyday scenarios that tell us people don't get enough sleep." Walker said.

"While it is early days," he added, "clinical evidence has shown that some form of sleep disruption is present in almost all psychiatric disorders. These findings may offer new mechanisms as to why, and provide novel insights into how we can understand and even treat these disorders at a brain level. My job now is to figure out what kind of sleep."

Source: Yoo SS, Jolesz FA, Gujar N, Hu P, Walker MP. The human emotional brain without sleep - a prefrontal amygdale disconnect. Curr Biol. 2007 Oct 23;17(20):877-878 [Abstract]


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This research makes alot of sense. I was sleep deprived for much of my life and the article has given me one explaination of my rollercoaster emotional state for those years. Thanks
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