Connection between sleep disruption and mood disorders including bipolar disorder

Scientists have confirmed what every newborn-cradling, sleep-deprived parent knows: that lack of sleep is connected to an inability to cope with normal emotional challenges.

They also theorize that sleep deprivation is linked to psychiatric ailments such as anxiety, depression and bipolar disorder.

When people, such as new parents, get little sleep, the amygdala, the region of the brain that alerts the body to protect itself in times of danger, goes into overdrive, scientists say. This in turn shuts down the prefrontal cortex, which commands logical reasoning.

Scientists at the University of California at Berkeley and Harvard Medical School have found that the amygdala, the region of the brain that alerts the body to protect itself in times of danger, goes into overdrive on no sleep. This in turn 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.

The findings are published Oct. 22 in the journal Current Biology.

"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, in a release.

The researchers studied 26 healthy participants aged 18 to 30, splitting them into two groups with 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.

The participants' brains were scanned with magnetic resonance imaging while they were exposed to images that ranged from neutral to very negative. The brain responses of the participants were measured.

Researchers found that the amygdala became hyperactive in response to negative visual stimuli such as mutilated bodies, children with tumors and other gory images in study participants who stayed awake for 35 hours straight.

Brain scans of those who got a full night's sleep in their own beds showed normal activity in the amygdala.

"The emotional centres of the brain were over 60 per cent more reactive under conditions of sleep deprivation than in subjects who had obtained a normal night of sleep," Walker said.

The researchers feel that the findings point to a connection between sleep disruption and mood disorders, including bipolar disorder.