Just One Night Without Sleep Can 'Rewire' Our Brains for Days

We have all sacrificed a night's sleep at some point in our lives, perhaps to study for an exam or while taking a long-haul flight. But just one night without sleep is actually enough to rewire our brains for days, scientists have found.

People who pull "all-nighters"—the practice of staying awake all night—may be familiar with a giddy, slap-happy and wired feeling, although the body is physically exhausted.

Neurobiologists at Northwestern University have found that this is a result of sleep deprivation actively rewiring the brain, a new study published in Neuron reports.

The scientists assessed mice who had been mildly sleep-deprived to analyze the effects of this on their bodies. They found more dopamine was released during all-nighters, and synaptic plasticity increased. And strangely enough, this is similar to the effects that antidepressants have on the brain.

"We expect that neural rewiring—provoked by a specific stimulus like brief sleep loss—can initiate a cascade of neuronal changes that outlast the immediate phase," Yevgenia Kozorovitskiy, an associate professor of neurobiology at Northwestern and corresponding author of the paper told Newsweek.

"For example, dopamine increase during brief loss can enhance neuroplasticity, and a subset of those new connections between neurons could persist. At the level of effects on mood, clinical studies show that interventions to circadian rhythms (or chronotherapies) can substantially enhance mood for a matter of days to weeks."

Scientists already know that a lack of sleep can change a person's mental state—the study notes an example where disrupted sleep patterns trigger mania or sometimes even reverse depressive episodes.

"Yet, precisely translating the duration of effects from an experience that induces neuroplasticity in the brain and changes behavior across different animals (e.g., from mice to humans) is not often straightforward," Kozorovitskiy said. "There are important differences across species in how our brains are wired and how they rewire. In our study, one episode of brief sleep loss led to an antidepressant-like effect that lasted at least 72 hours.

"This is very similar to the duration of effects of a single dose of the antidepressant ketamine on mouse behavior. However, for people receiving ketamine for depression, one treatment can have mood-enhancing effects for two weeks, sometimes longer, so we would not be surprised if the effects of brief sleep loss on the brain and on our mood persist well beyond the next day or two."

The mice used in the research—who were kept awake enough so that they were still comfortable without being too stressed—became more aggressive, hyperactive and hypersexual following periods without sleep. This was compared to their behavior when they had a normal amount of sleep and their activity was much calmer.

Once it became clear that a higher amount of dopamine was released during sleep loss, Kozorovitskiy and colleagues began to look at the four regions of the brain responsible for dopamine release.

They found that three out of the four—the prefrontal cortex, nucleus accumbens and hypothalamus—were triggered during periods of no sleep.

Signs of hyperactivity disappeared after a few hours; however, this "antidepressant effect" was still present.

From this research, it is clear that acute sleep deprivation somehow "[activates] to an organism," Kozorovitskiy said.

"It is reasonable to expect that frequent 'all-nighters' would adversely affect our ability to regulate our moods," Kozorovitskiy told Newsweek. "This could occur through overdrive on the types of mechanisms we found in this study, but also because of more severe, distinct changes caused by more chronic sleep disruption, leading to metabolic stress. We know this enhances the risk for developing many disorders."

Although these findings may suggest pulling an all-nighter as a way to cure a blue mood, the scientists warn against this.

There are other, healthier ways to increase dopamine levels while getting enough sleep each night, such as "hitting the gym or going for a nice walk," Kozorovitskiy says.

But these findings are very important in the research for antidepressants and matching people to the right medication in this area.

"In future studies, we would like to understand what it is exactly in the state of sleep loss that causes dopamine neurons to become more active when we should be asleep but aren't," Kozorovitskiy said. "Do different causes of sleep loss lead to the same changes in the brain? For example, sleep loss from staying up studying for exams may be processed differently in our brain compared to sleep disruptions that parents of new babies sustain.

"Are there hormonal and neural mechanisms that enhance resilience in the brains of new parents, and can we mimic them with normal sleep to help individuals with mood disorders or sleep disruptions?"

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about sleep deprivation? Let us know via science@newsweek.com.