Lack of sleep sends emotions off the deep end

— -- You might have guessed it, but now researchers have real proof: Sleep deprivation causes our emotions to go haywire.

That's according to the first neurological probe into the emotional brain without sleep. It was carried out by researchers at the University of California-Berkeley and Harvard Medical School.

"Most people think that when you're sleep-deprived, what happens to the brain is that it becomes sleepy and less active," says Matthew Walker, assistant professor of psychology at Berkeley and a former Harvard sleep researcher. But Walker says the imaging study published in today's issue of Current Biology found that the brain's emotional centers become "60% more reactive."

The study also suggests that lack of sleep elevates activity in the emotional centers of the brain most closely associated with psychiatric disorders such as depression.

Walker's team studied 26 people ages 18 to 30 who were divided into two groups. The sleep-deprived group was awake 35 hours; the other group slept normally.

Using the brain scans, the researchers showed participants a series of images, from neutral to increasingly negative and disturbing. The responses of both groups showed up as hot spots, but the sleep-deprived evoked stronger responses because the prefrontal area of the brain that normally sends out inhibiting signals wasn't able to keep emotions in check.

Though the thinking has been that psychiatric disorders cause poor sleep, Walker says now he's not so sure because those he studied didn't have psychiatric conditions, yet they exhibited emotional brain reactions similar to psychiatric conditions.

Mary Carskadon, a professor of psychiatry and human behavior at Brown University who has studied adolescents and sleep deprivation, says the new study is compatible with her findings. She is particularly concerned about what it means for adolescents, who are often sleep-deprived and who are being diagnosed with depression in increasing numbers.

"What we don't know is whether early sleep deprivation then projects out to things like major depressive disorder or bipolar illness and whether we're really setting up our kids for these major problems as they grow up," she says.