You spend about two hours per night dreaming. You don’t remember most of it—otherwise, sleep would be downright exhausting—but occasionally, you’ll wake up wondering what made you dream of eating a bowl of cereal in swimwear at the DMV (and unfortunately, ahem, we can’t answer that for you).

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Dreams can be incredibly confusing, and despite decades of research, scientists still have plenty of unanswered questions about the role that REM sleep—the sleep stage where the most vivid dreams occur—plays in our waking lives. Still, we looked into the science and found some pretty surprising things.

1. We might be in a dream deprivation epidemic.

Some research suggests that we’re not dreaming as much as we used to. In a paper published in the New York Academy of Sciences, University of Arizona professor Rubin Naiman made the case that REM sleep loss is a public health emergency. Naiman claims that Americans are dreaming less than ever before, and that dream loss could contribute to “illness, depression, and an erosion of consciousness.”

“In my life, it’s been the greatest concern,” Naiman tells Urbo. “We’re dreaming less, for lots of reasons—some of them biomedical, some of them psychosocial. But we are dreaming a lot less, and even the quality of our dreams are severely compromised.”

In his paper, Naiman cites an increase in sleep disorders as evidence for the epidemic. Somewhere between 50 and 70 million Americans are thought to suffer from sleep disorders, according to the Centers for Disease Control and Prevention. About 4 percent of American adults use some type of medication to get to sleep, and Naiman notes that many of those medications affect the way that we dream.

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That’s a big problem, as dreams seem to play an important role in the way that our brains encode memories. We’re not exactly sure how that mechanism works, but boy, it’s a fascinating mechanism.

2. Scientists aren’t totally sure what dreams do, but we’ve got some ideas.

Researchers have a few theories as to the purpose of REM sleep, but it’s a fairly complex issue, and there probably isn’t a simple answer.

“As hard as we might try to reduce dreams to brain chemistry, it’s another world,” Naiman says.

During REM sleep, the brain becomes sort of a second gut, in that it metaphorically chews on, swallows, digests, sifts through, excretes, and assimilates experiences.

“What we know is that we process lots of bits of information during the day. Most of it just goes in without a thought. For instance, I can look at this tree in my yard, and I don’t really have to think about it. But there are many experiences that stop us in our tracks. Today, I heard about the death of a friend of a friend; that doesn’t go down easy.”

Naiman believes that the process of dreaming helps our brains “digest” emotionally charged events, allowing us to encode them in our memory.

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“When we drink water, water doesn’t need to be digested,” he explains, “but there are certain foods we eat that requires a lot of digestive action. Our brain works similarly. During REM sleep, the brain becomes sort of a second gut, in that it metaphorically chews on, swallows, digests, sifts through, excretes, and assimilates experiences.”

Yes, the metaphor got a bit disgusting towards the end. In any case, there’s scientific support for that theory. In 2012, UCLA researchers showed that the sleeping brain behaves as if it’s recalling memories. The brain science is, in a word, complicated (brain science tends to get that way), but the research supports the idea that we shuffle memories around when we sleep in order to store them more effectively.

If you’re not able to dream, you might be at risk of developing certain conditions. For instance, some research shows that REM sleep deprivation might increase a person’s chances of developing post-traumatic stress disorder after a traumatic event. Naiman attributes this to an inability to “digest” the traumatic memory.

“We’ve known for years that the sleep and dream patterns of depressed people look exactly like the sleeping and dreaming patterns we observe in animal subjects who have intentionally had their dreams removed,” Naiman says. “It’s poor digestion, psychologically.”

3. Even a bad dream can be helpful.

By some estimates, 70 percent of dreams involve a threatening situation. Nobody enjoys having bad dreams, but even those seem to serve a purpose.

“Bad dreams involve processing challenging experiences, and there can be a really good outcome,” Naiman says. “After all, waking life is filled with challenging experiences.”

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If you have an unpleasant dream about giving a bad presentation during a stressful period at work, that’s understandable; your brain is simply dealing with the stress. Nightmares, however, aren’t the same thing as bad dreams.

“A bad dream becomes a nightmare when it’s so intense that it wakes us up,” Naiman notes. “And with a nightmare—and this is particularly true for post-traumatic nightmares—the digestion isn’t finished. Chronic nightmares are examples of incomplete dreaming.”

One popular theory holds that dream consciousness is an evolutionary mechanism; it allows our body to simulate threatening events rapidly and repeatedly. That allows us to manage our emotions when those threatening situations present themselves.

Our ancestors might have dreamt about lion attacks, and when a real lion attack occurred, they had the emotional tools they needed to respond to the threat appropriately. We’re carrying out the same basic process when dreaming about that time that our crush told us that our fly was down. The dream might be bad, but it still serves an important purpose: It helps us stay calm when it happens again.

4. Symbols in your dreams can be enormously meaningful (or completely meaningless).

For thousands of years, humans have obsessed about the symbols we see in our dreams. Sigmund Freud wrote extensive diatribes on the topic, emphasizing the importance of the subconscious mind.

Naiman agrees on that point, but he notes that dream symbology is extremely subjective.

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“Dreams operate on entirely different logic than the waking world,” he says. “The most popular dream books for consumers today are called dream dictionaries. If you dream about an apple, you can look it up under ‘A,’ and find out that an apple represents sex, right?”

Well, maybe to some of the Macbook fiends in our office, but we get Naiman’s point.

Think about your personal associations to the symbols [in your dreams]. …Recognize that our brains draw upon the vastness of our personal and cultural experiences to make meaning.

“Most dreamwork is based on an unexamined tenant that says, ‘As it is in the waking world, so it is in this more expansive dream world,’ he says. “That suggests that I can understand the dream world by comparing the images in their waking-world counterpart. That downsizes the dream—it reduces it, and I think that it’s a huge mistake.”

Dream symbology assumes that the unconscious mind is uniform, which obviously isn’t true; a bad dream about a dog could mean something specific to a veterinarian and something entirely different to a mailman.

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“[Dream symbology] presumes that there’s nothing personal in a dream,” Naiman says. “Ultimately, that type of interpretation is a way of diverting our attention from the unconscious.”

Modern psychologists generally agree on that point; while dreams deserve attention, their symbols vary greatly from person to person.

“I tell my patients to reduce the dream to its most basic emotional plotline,” clinical psychologist Dana Harron, PsyD, tells Urbo. “Think about your personal associations to the symbols [in your dreams]. …Recognize that our brains draw upon the vastness of our personal and cultural experiences to make meaning.”

Naiman believes that we can improve the benefits of our dreams by making a few practical changes.

Let’s say that you’re committed to getting more in touch with the non-waking world. What can you do?

“In terms of practicality, people can learn to access their own dreams in a simple way,” Naiman says. “When we awaken in the morning, we’re typically waking up out of a dream; the term we use to describe that, in the Western world, is ‘grogginess.'”

“It’s a simple practice to not leap out of bed in the morning. Preferably, you should wake up without an alarm and linger in your grogginess, without intention. If we chase the dream, it’s skittish, and it will run. If we just linger, then images will start to show. At that point, the practice is to start recording those dreams when we wake up. Talk about it to a partner, write about it in a journal. The more we do that, the more solid the bridge that we build between the dream world and the waking world.”

I think that what’s more important than knowing the meaning of any particular dream is really understanding that dreaming itself is meaningful.

Studies suggest that documenting dreams can improve recall significantly, so consider keeping a pad of paper and a pen on your nightstand.

“Keep a dream journal,” recommends Harron. “When you wake up, jot down three to five words if you don’t have time to write a complete entry. You spend a third of your life dreaming, and you can learn so much if you pay attention.”

Naiman says that dreaming can actually be a creative exercise.

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“I think it brings up the artist, the poet, the spiritual part of each of us,” he says, “and this is all independent of analyzing the dream. I think that what’s more important than knowing the meaning of any particular dream is really understanding that dreaming itself is meaningful. We don’t have to know the meaning of everything, but we can begin to trust that process.”

“I think dreaming can change that. I think if we had an open-hearted relationship with a dream, we develop what psychologists would call self-efficacy. …We deepen our faith in who we are, where we recognize there’s a deep part of us that’s on our side that’s supportive and intelligent.”