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© Patryk HardziejDreams play a key role in boosting creative thought, memory, learning and even mental health. Now modern life may be cutting them short, with serious consequences
YOU know that feeling when someone wakes you up in the middle of a really good dream? There is a real sense of loss, like ending a TV episode on a cliffhanger. You want to jump back in, but no such luck.

That is me every morning. I have a baby sleeping in the same room and am wrenched awake early each day, often mid-dream.

That might sound like a trivial complaint. We tend to think of dream sleep as unimportant, the poor relative of vital and restorative deep sleep. But now it seems that dreams are much more than mystical night-time adventures. Recent research suggests that rapid eye movement (REM) sleep - when we have the most powerful dreams - is vital to learning and creativity, and promotes a healthy mind in a variety of ways. It isn't romantic whimsy to say that if we stifle our dreams, we aren't going to reach our potential.

Chronic dream deprivation isn't just a problem for people with small children. Going to bed drunk or stoned, taking various medications or even just using an alarm to wake up in the morning can all leave your dreams smothered. So, currently sleep deprived, I wanted to find out if missing out on dream sleep is as bad as it seems, and if so, what we can do to get our dreams back.

The idea that sleep is vital for good health is now so prevalent you would have to be sleepwalking through life to miss it. Not only does scrimping on sleep leave you emotionally fraught and struggling to make decisions, it can also mess with your immune system, has been linked to metabolic diseases like obesity and type 2 diabetes, and is implicated in Alzheimer's disease and many mental health problems including depression.

Based on what we know about sleep, the US National Sleep Foundation recommends that adults should get between 7 and 9 hours per night. The problem is we don't. A 2015 survey found that only 35 per cent of people in the US were getting that amount. In the UK, 60 per cent of people report getting less than 7 hours a night. Our lack of sleep has been dubbed an emerging global epidemic.

Even so, we tend not to prioritise sleep as we might other aspects of our health. I used to think that if I managed to get a decent core of sleep - say, 6 hours - that would do the trick, because most of the health benefits of sleep have been linked to the deep sleep we get at the beginning of the night.

But as we probe deeper into the effects of sleep on health, that picture is changing. Some are even suggesting we are experiencing an epidemic of REM sleep loss. We aren't just sleep-deprived, says Rubin Naiman at the Arizona Center for Integrative Medicine in Tucson, we are dream-deprived.

To look at what's going on, let's start with my unwelcome, early morning wake-up call. Sleep occurs in repeating cycles each about 90 minutes long. In each cycle, there are three stages of non-REM sleep, where brain activity becomes gentle and rhythmic, eventually heading into slow-wave, deep sleep. After slow-wave sleep, the brainwaves change pattern again, the eyes start roiling under their lids and most of the muscles in the body become paralysed to stop us acting out our dreams. This is REM sleep, and the proportion of time spent in this stage increases in each successive sleep cycle throughout the night, so that by early morning, much of those 90 minutes can be spent in REM (see "To sleep, perchance to dream").

We do dream in other stages of sleep, but these dreams tend to be unemotional, concerned with simple things and hard to remember. In short, they are boring. REM sleep is where classic dreams occur, those with bizarre juxtapositions, physically impossible feats, and emotional and puzzling events.

If you wake up to an alarm clock (or a baby), you lose all that. "If you are using REM as a proxy for dreaming then yes, dreams are being curtailed," says Tore Nielsen at the Dream and Nightmare Laboratory in Montreal. Of course, it is hard to disentangle the effects of REM sleep itself and the dreams that come with it. But Naiman goes as far as to say that dream loss is an unrecognised public health hazard. "Sleep medicine should be called sleep and dream medicine," he says.
© Patryk Harkziej
Some of the biggest effects seem to be around learning, memory and creativity. For instance, last year Sylvain Williams and his colleagues at McGill University in Montreal showed what a lack of REM sleep does to mice. By depriving the hippocampus, the part of the brain where memories are stored, of the brainwaves generated during this type of sleep, the team showed that the mice couldn't consolidate memories about tasks they had learned the day before. When they disrupted the hippocampus in a similar way when the mice were awake or in non-REM sleep, they found the animals were able to form memories as normal.

Any interference with REM sleep will have deleterious consequences, says György Buzsáki at the Neuroscience Institute at New York University. "There is a good reason why nature invented sleep with REM as its critical ingredient," he says.

Sleep on it

Another benefit of REM sleep and the dreams that go with it seems to be a creativity boost. Sara Mednick at the University of California, Irvine, measured people's creativity after allowing them to either rest quietly, to have a nap of non-REM sleep or to have a nap. The volunteers were then asked to find a word that links three others. For example, "cookies", "heart" and "sixteen" are linked by the word "sweet". Those who had had REM sleep during their nap showed improved creative ability, compared with those who had none.

That makes sense when you consider that REM sleep seems to specifically put the brain into a state where it is unable to find the associations between things you might expect. This results in those most bizarre of dreams where you meet people at the bottom of the ocean and think nothing of breathing water, or talk with long-dead relatives.

In fact, several researchers think this madcap associative quality is key to the role of REM. Perhaps part of its function is to force us into a creative state.

This opens the door to assigning a function to dreams themselves. For years it has been considered taboo to speculate on their purpose. Many scientists will admit only that they are a diverting consequence of REM sleep.

Robert Stickgold at Harvard Medical School, whose work has shown that the majority of dreams have emotional cores, thinks there is more to it than that. "One of the reasons we dream is so we have emotional reactions," he says. "They are part of the mechanism the brain has to choose amongst potential interpretations." So you might dream about a hard decision, and the brain monitors your emotional response to it. The next day, your ability to make the decision is easier: you have "slept on it". This phrase or similar exists in most languages, by the way.

Naiman goes even further. You may have heard the digestive system being described as a "second brain", in reference to the fact there are large numbers of neurons connecting the gut and the brain; you literally get "gut feelings". Analogously, Naiman calls the dreaming brain a second gut. "It processes undigested material from the day," he says. "If you sleep well and dream, you heal more quickly from emotional hardship."

There is tentative evidence to back up the idea. Rosalind Cartwright at Rush University in Chicago has reported that the dreams of women who have depression after a difficult divorce may aid their recovery. Women who reported a greater number of negative dreams about their ex-spouses soon after the divorce were more likely to be in remission a year later than women who didn't report any. Perhaps they were "digesting" their negative feelings.

Naiman calls this digestive theory of dreaming endogenous, or internal, psychotherapy. It follows the ideas of Els van der Helm and Matthew Walker at the University of California, Berkeley, who have proposed that REM sleep is "overnight therapy" that strips out the emotion from traumatic or potentially anxiety-inducing memories.

Van der Helm and her colleagues discovered that sleep dampens our emotional response to provocative images. They tested people in a brain scanner at the end of the day or after a night's sleep in the lab, and found that the brain's emotional centre is less active after sleep. The effect was stronger after REM sleep, especially when dreams were unpleasant.

Traumatic recall

Their work has also shown that, in most people, REM sleep plays a similar role when it comes to memories: it strengthens emotional recollections, but at the same time weakens the emotional "tone" of the memory. "This allows you to process emotional memories and ensure you don't completely relive them whenever you are reminded of them," says van der Helm. On the other hand, people with depression have excess REM sleep, which may overemphasise negative emotions. As a result, those with the condition may wrongly perceive their life to be dominated by bad events.

This process also goes awry in post-traumatic stress disorder, whereby intense emotions associated with memories aren't stripped away during sleep. "The emotional tone remains incredibly high and that causes people to relive the traumatic experience over and over again," says van der Helm. Not only that, but the memory becomes overgeneralised too, meaning many different cues can trigger recollections of the traumatic event - a car door slamming might bring back the sound of a gunshot, for example. Why this happens isn't yet known, but it may be that high adrenaline resulting from the stressful situation disrupts the workings of the brain. "Good sleep immediately after the traumatic event seems to be a protective factor," says van der Helm.

Given the potential benefits of dream sleep, it is worrying that there is a long list of behaviours that seem to diminish it.

Aside from early rising - a 2011 YouGov survey in the US found that 60 per cent of people rely on an alarm to wake up - drinking alcohol is perhaps the most common. If you go to bed drunk, or even slightly tipsy, your sleep profile will skew to deep sleep. Even a single drink will delay the first period of REM.

Many people deliberately use alcohol to get them off to sleep, but may be unaware of its effect on their sleep quality. "Alcohol is a specific REM suppressant," says Stickgold. If you drink a lot before bed, you wake throughout the night as the body processes the alcohol. "So there's a lot of disruption and you wake up, even though you feel like you're dead," he says.

Marijuana also promotes deep sleep and suppresses REM: go to bed stoned and you won't dream. Heavy users of cannabis report a startling dream "rebound" when they stop taking the drug. In this, REM sleep comes back with a vengeance, and with it all the dreams they have been missing - further evidence that it probably serves an important purpose.

With other compounds, the effects differ. Zolpidem (sold as Ambien) is a sedative that happens to reduce REM. Many antidepressants do the same, promoting deep sleep to the detriment of REM. The confounding factor here is that depression itself can result in too much REM sleep. "If you're taking sleep meds or antidepressants, they might help you stay smart at the cost of being wise," says Stickgold. "Smart is being able to remember everything that was said in a conversation and wise is being able to tell what parts were any use at all." Many sleep disorders, including sleep apnoea, where people stop breathing during the night, and insomnia, disrupt the cycle of sleep phases and reduce REM too.

That said, we don't yet have the hard data to support the idea that we are getting less REM sleep, let alone that we are losing our dreams altogether. Unless we wire everyone up and monitor their brainwaves while they sleep, we can only infer what is occurring to our sleep profiles based on sleep habits. But the logic and supporting evidence that something is happening are strong. Sleep scientists I spoke to broadly accepted the idea.

Given our new understanding of the role of REM, if modern lifestyles really are reducing our dream time, we could be sleepwalking into a load of trouble. Yet despite the mounting evidence, there remains disagreement over what exactly REM sleep does, and crucially, how much harm comes from missing out on it. The proportion of REM sleep varies wildly across animal species, and doesn't seem to have a predictable effect on health.

And showing an effect in the lab is very different to the real world. If we are acutely deprived of slow-wave sleep there are obvious effects, such as falling asleep at the wheel. With REM sleep, the effects are far more subtle. Mednick thinks we don't know enough about what REM sleep does to say there is a loss-of-REM crisis. But we should take this phase of sleep more seriously. We should consider it in the same way an athlete scrutinises diet and training, she says, but this isn't socially acceptable at the moment. "You can't say, 'I really need to work on my perceptual abilities more and I need to be more creative so I really need to take a high-REM nap right now'."

From now on, this is something I am going to aspire to. I will pay more attention to my sleep cycle and try to make time for some quality REM (See "5 ways to boost your dreams and improve your health"). I am also resolved to value my dream time more for its own sake - what Naiman calls "perceptual yoga".

When I spoke to Naiman it was 7 am his time. It sounded beautiful - he could see the sun rising above the Arizona mountains. But hang on, 7 am is peak time for REM activity, so why isn't he asleep? "I get up early, so I have empathy for all the people I meet who are dream-deprived," he says.