You probably know that quality sleep is integral to your overall health: it helps strengthen the immune system, improves mood, helps control weight, lowers stress—and so much more.
But you might not know that REM sleep—the phase of sleep where dreams mostly occur—may play important functions for memory and mental health, says Philip Cheng, Ph. D., clinical psychologist and research scientist at the Sleep Disorders and Research Center at Henry Ford Health.
Here, he answers everything you’ve wanted to know about dreams—surprising health benefits included.
Q: First of all, why do we dream?
A: Historically, psychologists have had lots of theories about dreams, ranging from dreams representing our unconscious desires to dreams being random and having no inherent meaning. But newer studies suggest that dreams may have dedicated functions.
During REM sleep, we often have muscle twitches. And some studies suggest that these twitches may help wire our brains to improve motor development. One study tested the strength of the reflexes, and the reflexes that were targeted (or made to twitch) during sleep were better developed than those that weren’t targeted during sleep. Although it’s not the only reason why children and babies sleep more often, this is likely one function of sleep in childhood development.
Evidence also suggests that REM sleep may help our memory by strengthening neural connections in the brain. This means that if you prioritize sleep when you are solving a new problem or learning a new skill (such as how to volley a tennis ball), you are likely to see improvements after sleeping as opposed to staying awake.
Q: Does this mean that you should take lessons closer to bedtime instead of in the morning?
A: There is some evidence to support that learning something closer to bedtime may have some benefit. However, there is an important trade-off. Exercising close to bedtime can make it harder to fall asleep. Overall, people should prioritize sleep in order to promote learning.
Q: What are the health benefits of dreaming?
A: One health benefit researchers have found is that REM sleep helps reduce the emotional tone of our memories. This means that when something stressful or traumatic happens to you, the REM phase of sleep helps to gradually decrease your emotional response to that event.
Another more evolutionary health benefit is that dreaming is a way for our brains to prepare us for dangerous events. For example, when we see a lion, we want to quickly recognize it’s dangerous and run away. It’s not advantageous to learn that when we encounter a lion in real life, because it’s such a high stakes situation—you could be eaten if you don’t react fast enough.
Instead, dreams are a way for us to practice our response to a stressful situation so that if it happens in real time, the brain can respond quickly and reduce the likelihood of being harmed.
Q: So do we actually learn in our dreams?
A: It’s less like learning and more like rehearsing. Dreaming sharpens information. For example, when you’re learning French in a classroom, maybe you’re paying attention to the professor talking, maybe classmates are having a side conversation. There’s a lot of information coming out of this French class that you’re processing—it’s not just the French.
Sleep strips away the less important stuff and helps you hold onto what’s most important. So if you’re dreaming about your French class, the less important stuff fades away and you remember the key points.
REM sleep doesn’t actually make our brains decide what information to ignore and what information to remember, but it is a mechanism that helps the decision-making process. Rehearsal and emotional importance are what helps us decide.
Q: Do we dream every night?
A: Most of us have REM sleep every night, so the idea is that we do dream every night. If you wake up during REM sleep, you’re more likely to remember your dream because that was the last thing that was going on. If you wake up during another phase of sleep, you’re less likely to remember your dream.
Also, the more emotionally important your dream is, the more likely it is that you’ll remember it. It’s the same reason people remember exactly where they were during 9/11 but they can’t remember what they ate for lunch a week ago.
Q: Why do we, collectively as people, often have the same dream themes?
A: There are common dreams you hear about: teeth falling out, not being prepared for a test, showing up somewhere naked. We probably have these common dreams because we have shared experiences. In the same way that we can make movies and books that are relatable to a lot of people, we all have shared concerns and shared stressors that manifest in our dreams.
Q: Can our dreams affect our mood?
A: Yes, definitely—and vice versa. There is some anecdotal evidence that when people are depressed, their dreams get more violent or vivid. There’s a shared acceptance that dreams can both reflect and impact our emotional states.
There’s a subculture of people who are really into lucid dreaming—or the ability to have control in your dreams—in which case they could control the emotional state or mood of their dream.
There are certain techniques people use to try to train their brains to be able to lucid dream, but lucid dreaming isn’t completely scientifically understood. Our lab ran a study on it a few years ago. Our approach was to stimulate the frontal cortex of the brain with electrodes. The idea was that if we can get the frontal cortex a little more energized during the dream state—because that’s where planning and decision making happens—the more likely it is that you can control your dreams.
Q: Does lucid dreaming have any health benefits?
A: I would say it does for those who have PTSD. When you have PTSD, a lot of your symptoms occur in nightmares. And if lucid dreaming can allow you to reduce the stressfulness of these nightmares, then absolutely, you’d see an improvement in your symptoms.
If you have sleep concerns, make an appointment with a sleep specialist. Call 1-800-436-7936 or visit henryford.com/sleep to learn more.
Dr. Philip Cheng is a clinical psychologist and sleep research scientist with Henry Ford Hospital in Detroit.
