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REM sleep can reset your brain after an upsetting event

When something upsetting happens, my 100-year-old grandmother always suggests that I might feel differently about it the next morning. It turns out that her folk logic could be totally in line with current science. A small new study from the Netherlands shows that “sleeping on it” is a scientifically sound strategy when you’re dealing with stress.

The study’s researchers put participants in an MRI machine and exposed them to a smell that they found upsetting. (The findings don’t specify what the smells were, but I’m so curious. Poop? Toxic waste?) Scientists saw that the amygdala, the part of the brain responsible for processing emotions, was activated by the presence of the odor. Participants then slept a full REM sleep cycle. REM is the sleep phase in which the brain is most active — that quality sleep often produces vivid dreams, many of which you can actually remember.

When the people in the study were exposed to the smells again, the amygdala remained inactive, meaning they no longer had as much of an emotional response to the odors. It wasn’t that the participants had gotten used to the smell, it was that their brains had processed the emotions they associated with the smell and no longer found it as upsetting. This means that these people re-wired their negative emotional responses overnight I asked some sleep experts to explain how this works.

“REM sleep is considered a time when the brain can process emotional memories, and ‘pack them away,” says Alex Dimitriu, a psychiatrist and sleep specialist at Menlo Park Psychiatry and Sleep Medicine in the San Francisco Bay Area. “When everything is working well, we experience unpleasant — and pleasant — situations, and our brains ‘rehearse’ and process these memories through the night. Like the process of therapy, which REM sleep has been compared to, this helps consolidate and safely store these experiences.”

“There’s a thought that REM sleep has to do with memory consolidation,” says Christopher Winter, a neurologist and author of The Sleep Solution: Why Your Sleep is Broken and How to Fix it. “During REM, our brains figure out what kind of memories we’re going to hang on to and what we’re going to get rid of. REM sleep can help overlay the interpretation of an event and help our brains decide whether it is stressful or not.”

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Basically, vivid dreams are our brains doing housekeeping. While we sleep, our bodies are sifting through our memories, deciding what’s important enough to keep, what we should throw out, and how we are going to respond to the memories that we keep. REM sleep gives the body time to decide that what we once experienced as stressful, like the odors the participants in the study were exposed to, doesn’t feel as stressful as they did before. This could explain why a terrible fight with your boo could feel less catastrophic after you’ve slept on it. And it offers us a practical and accessible way to deal with both everyday stressors and traumas. Unlike the many kinds of “self-care” that aren’t much more than marketing gimmicks, sleep is free and readily available to most folks.

What does this mean in practical terms? It means that getting enough sleep is an very real way to reduce stress in our lives, not just because our bodies feel less tired, but because we will have had a chance to do some of the important emotional sorting that can reduce our reactivity to stressors.

“There has been a lot of evidence suggesting that REM sleep is more about processing and preparing for emotional situations,” Dimitriu says. And, Winter adds, there are ways that we can use this intentionally. We always tell people to try not to think about stressful things when they’re trying to sleep, but Winter suggests that it might be more effective to do the opposite. “Try to think about the event,” he says, “Imaginatively rehearse or reenact the event so that it plays out in a positive way, and then when you get good quality sleep, the body starts to reframe the event in a less stressful way.”