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7 weird and terrible effects of sleep deprivation

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Roughly half the adults in the United States say that they don't get enough sleep. And that's more than just a bother. There's a growing body of research showing that sleep deprivation is related to all sorts of problems — from increased risk of vehicle crashes to health problems like heart disease and anxiety disorders.

But scientists have only just begun to study sleep deprivation in more detail. New neuroscience tools — such as ones used to image the brain — have helped create a boom in sleep research in the past decade. The field is still young, and some pretty basic questions are still unanswered: why so many hours? Why do we dream?

Sleep-deprivation studies are one way that researchers try to figure out what's going on. These studies can vary widely: some ask participants to go without sleep for just one night. Others mandate odd, restricted sleep schedules for weeks.

Published research already shows that going without enough sleep for one night can decrease attention span, slow down people's reaction times, and cause memory problems, irritability, and a rise in the hunger hormone ghrelin. Sleep is fundamentally linked to an exceptionally broad range of necessary human functions — and lack of sleep can mess people up.

But it might get even weirder than that. This spring, at the 28th meeting of the Associated Professional Sleep Societies, sleep researchers shared some of their preliminary work on how sleep deprivation might mess us up in all sorts of unexpected ways — like making people less empathetic and less sensitive to gambling losses. It's also possible that sleep-deprived people don't even realize how sleep-deprived they are.

It's important to note that results presented at a conference aren't necessarily solid. They're usually preliminary findings, some of which might never be published in a journal because they don't pan out. There are a lot of unknowns here. Still, it's worth taking a look at where recent sleep research is going. Here are the seven unexpected ways sleep deprivation might mess us up:

1) People who are sleep-deprived may not even realize they're sleep-deprived.

The more sleep-deprived people were, the less well they did on a classic reaction-time test administered by scientists, according to one presentation from Kirsi-Marja Zitting of Harvard Medical School and colleagues. That seems unsurprising.

But there was a twist: sleep-deprived people often thought they were doing just fine. A separate presentation suggested that sleep-deprived people couldn't accurately assess how alert they were, either.

2) Sleep-deprivation might give you "beer goggles."

Or, more accurately, sleep goggles. After 24 hours of sleep deprivation, men in one experiment rated photos of "the least attractive models" as more attractive than before they'd gotten all sleepy. There was no observable effect for women, according to Jennifer Peszka, of Hendrix College in Arkansas, and her team.

A previous experiment that she presented at 2013's conference suggested that men who were sleep deprived also mistakenly thought that women were more interested in having sex with them.

3) Lack of sleep seems to make people more sensitive to pain.

Subjects allowed two hours of sleep one night ended up decidedly wimpier — they were able to tolerate significantly less pain. This study was done by a team from Pusan Nation University Yangsan Hospital in South Korea, The University of Sydney and the Komoki Sleep Center in Seoul.

4) And less sleep also seems to make people less empathetic.

Subjects seemed to have less empathy when viewing photos of hands stung by needles. Researchers, including Torbjörn Åkerstedt, of Stockholm University, determined empathy levels by looking at activity in various areas of the brain.

5) Sleep deprivation could lead to increased paranoid and delusional beliefs.

After being awake for 18 hours straight, participants rated somewhat higher on standard scales of global paranoia. And sleepier people rated higher on depersonalization, which is feeling separated from your body, thoughts, or reality. This one was brought to you by Katarzyna Maczewska, of Newcastle upon Tyne NHS Foundation Trust, and colleagues.

6) Going without sleep seems to make people less concerned about losing money.

A group from the University of Pittsburgh, including Tyler Conrad, presented this one. Participants did a gambling task, where they could win $10 or lose $5 in each trial. When anticipating a loss, those who were sleep deprived showed less activity in the caudate and orbital frontal cortex brain regions, which are associated with the mind's reward system.

7) And sleepy people seem worse at recognizing other people's emotions.

People were worse at identifying the emotions on people's faces and how intense the emotions were. A possibly reason why: because they focused more on the lower part of the face. This one was from a group from the Université du Québec en Outaouais.

Many of the changes in the list of seven, above, were observed after just one night of thoroughly disturbed sleep. But in many cases, the idea is more that small effects from somewhat poor sleep many nights a week could add up to significant changes to one's body and behavior over a lifetime.

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Correction: A previous version misstated the location of Hendrix College.