Sleep to solve a problem

"Sleep on it. Things will look better in the morning."

This advice, often given by a parent, is said with love and good intentions, but it still makes us roll our eyes, because we just want to go to sleep — not think, not assess options. We certainly don't want to wait until tomorrow.

But …?

"We all do that," says Dr. Robert Stickgold, professor of psychiatry at Harvard Medical School. "We solve problems while we're asleep."

More importantly: we're supposed to. The brain is doing its nighttime job of finding connections, so when we wake up, we have a different take. It can feel like a stress, but rather than fight it, there are ways to accept the nightly review of the day so it doesn't turn into a sleepless assessment of our entire lives.

The first step is understanding how it works.

How the brain solves problems during sleep

When you're awake and trying to work through a sticky problem, the go-to approach is often taking a piece of paper and listing the pluses and minuses. But there are usually too many items, and you don't know how to sufficiently rate the importance of each one, so "it doesn't help you," Stickgold says.

But when you get into bed, the brain does a triage and "rifles through the events of the day and sees what's left unfinished," he says. It's picking out what has some "affective buzz," the emotions that happened during or shortly after something took place. The brain uses these memory "tags" as indicators that the event was important and that there's more to figure out. Essentially, the brain is saying, "I think I can help you."

Two elements make this happen. The prefrontal cortex gets shut down. This part of the brain handles executive decision-making (which includes rational thinking and impulse control), but now there's no critical edge or categories to put ideas in. The brain can freely associate and, as Stickgold says, "process in the background."

And when you get into the REM stage of sleep, the neuromodulators norepinephrine and serotonin are turned off. Norepinephrine enhances focus on immediate, concrete problems. "It's the reason you don't want to hear about someone's 'brilliant idea' when you're approaching a deadline," he says.

There's little known about what happens when serotonin is shut off, but Stickgold suggests it biases the brain into identifying looser connections as valuable. With both neurochemicals at bay, fragments of ideas can come together. "You have enhanced discovery of weak associations, ones you'd never notice," Stickgold says.

The result is that you wake up the next day suddenly thinking, "I don't want to take a job in Iowa," or "yeah, Iowa." It can feel like a gut decision, one you can't necessarily explain. It also may not be the final one, but something has shifted. "You're not in the same place as when you went to sleep," says Stickgold, adding that it can't all be explained, and science can't calculate whether what you decide is right. "It's a nonrational process."

Staying up to work on a problem doesn't work

You might be a person who turns problems over and over while waiting for sleep. What the brain wants to do before you fall asleep is see a thought and go to the next one. What you may end up doing is latching on to one thought, then you ruminate; regrets start creeping in, and that triggers a rush of adrenaline, which can take 10 to 15 minutes to burn off, Stickgold says.

It helps to acknowledge a thought and let it keep moving, similar to the practice of observing thoughts without judgment during meditation. There are a number of imagery devices that can work: having a ticker tape or balloon shuttle it away, or putting it on a tee and knocking it down the fairway. The main thing is to realize that the mere existence of the thought is not a problem.

But if thoughts persist, there are calming steps. If you are worrying whether the garage is closed or the oven is off, rather than continuing to wonder, "there's nothing wrong with getting up and checking," Stickgold says. For less immediately fixable issues, keep a notepad by your bed and write down a reminder for tomorrow. If you're worried you'll forget a particular concern or idea, this gets it out of your head and guarantees you'll see it in the morning.

What doesn't help is getting up in the middle of the night to "work" on a problem. You just end up being exhausted the next morning, and you're no closer to a decision or solution. The answer, however uncomfortable it might initially feel, is to let the thought parade march on through.

"Look at the period of fretting as a gift," Stickgold says. "It's setting up the brain for taking issues and lining them up for an incredibly productive eight hours. It's kind of elegant in a way."