When I’m giving a university lecture about dreaming I often start by asking if anyone would be willing to share a dream that I will interpret on the spot.
Here is a typical example from a student I’ll call Kyle. He says that in his dream he’s running through an underground car park to get to his car. He doesn’t know why he’s running, just that he has to find his car.
When he finds it, he tries to start it, but each time he turns the key nothing happens. His mobile phone rings and he wakes up.
I look knowingly at Kyle and say, ‘I know exactly what your dream is about, Kyle. It’s about time, and more specifically, about not having enough time to do the things you really want to do in life.’
A wave of recognition, almost relief, washes over Kyle’s face, and the rest of the class appear equally convinced.
Then I come clean. ‘Kyle, I have a confession. No matter what dream anyone ever tells me, I always give them that generic response, and it always seems to fit.’
Thankfully, Kyle is a good sport and takes this with no ill grace.
I explain that the reason I do this exercise is to show that Sigmund Freud, who believed that dreaming was a way for our unconscious mind to deal with whatever thoughts our conscious mind was repressing, was wrong.
This entirely nonscientific belief dominated psychiatry and psychology for a century.
By ‘interpreting’ a student’s dream, I can vividly demonstrate the dangers of generic interpretations that feel very persona, yet scientifically hold no specificity whatsoever.
I realise this all sounds rather dismissive, but I am in no way suggesting that reviewing your dreams yourself, or sharing them with someone else, is a waste of time.
On the contrary, I think it is a helpful thing to do, because dreams have a function — indeed, writing down your waking thoughts, feelings, and concerns has a proven mental health benefit, and the same appears true of your dreams.
Nevertheless, the psychoanalytic method built on Freudian theory is nonscientific and holds no repeatable, reliable, or systematic power for decoding dreams.
To be fair, the field of neuroscience was in its infancy when Freud was thinking about dreams. Science was simply not up to the task of deconstructing them.
Today we have the benefit of a much more informed, neuroscientific view of REM or rapid eye movement sleep, which is the principal sleep phase during which we dream. As a result, we now have scientifically testable theories of how we dream, and what it is that we dream about.
Neuroscience even gives the chance to nibble away at the most fascinating question in sleep science: WHY do we dream?
Some of the earliest rudimentary evidence came from my colleague Robert Stickgold at Harvard University who designed an experiment that would determine the extent to which dreams were a precise replay of our recent waking experiences. For two weeks, he had 29 healthy young adults keep a detailed log of daytime activities, and their emotional concerns.
In addition, he asked them to write down any dreams they recalled when they woke up. He then had external judges systematically compare the reports of the participants’ waking activities with their dream reports.
Of a total of 299 dream reports collected, a clear rerun of prior waking life events was found in just 1 to 2 per cent. Dreams are not, therefore, about simply rewinding the video of the day’s recorded experience and reliving it at night.
But the researchers did find one strong daytime link with night-time dream reports: emotions. Between 35 and 55 per cent of emotional themes and concerns that participants were having while they were awake during the day powerfully and clearly resurfaced in their dreams.
If there is a red-thread narrative that runs from our waking lives into our dreaming lives, it is that of emotional concerns. But contrary to Freudian assumptions, the scientists had shown that there is no censor or disguise.
Dream sources are transparent — clear enough for anyone to identify and recognise without the need for an interpreter.
It is said that time heals all wounds. Several years ago I decided to scientifically test this age-old wisdom, as I wondered whether an amendment was in order. Perhaps it was not time that heals all wounds, but rather time spent in dream sleep.
I had been developing a theory based on the combined patterns of brain activity and the brains’ chemical messengers during REM (dreaming sleep) — and from this theory came a specific prediction: REM-sleep dreaming offers a form of overnight therapy.
That is, REM-sleep dreaming takes the painful sting out of difficult, even traumatic, emotional episodes you have experienced during the day, offering emotional resolution when you awake the next morning.
At the heart of the theory was the astonishing change in the chemical cocktail of your brain that takes place during REM sleep. A key stress-related chemical called noradrenaline is completely shut off within your brain when you enter this dreaming sleep state.
In fact, REM sleep is the only time during the 24-hour period when your brain is completely devoid of this anxiety-triggering molecule. Noradrenaline is the brain equivalent to body chemical adrenaline.
I wondered whether the brain during REM sleep was reprocessing upsetting memory experiences and themes in this calm (low noradrenaline), ‘safe’ dreaming brain environment — creating a perfectly designed nocturnal soothing balm that removes the emotional sharp edges of daily lives?
If so, we should awake feeling better about distressing events that had happened before we dreamt.
Think back to your childhood and try to recall some of the strongest memories. You’ll notice almost all of them will be of an emotional nature: perhaps a particularly frightening experience of being separated from your parents, or almost being hit by a car.
Also notice, however, that your recall of these detailed memories is no longer accompanied by the same degree of emotion that was present at the time. They are no longer emotional memories. Instead, they are memories of an emotional event, but lack the original emotional charge.
My neurobiological theory of dreaming as therapy is that we have REM-sleep dreaming to thank for this dissolving of emotion from experience — like stripping the bitter rind off an orange. We can therefore learn and usefully recall salient life events without being crippled by the emotional baggage that those painful experiences originally carried.
That was the theory; next came the experimental test. We recruited a collection of healthy young adults and randomly assigned them to two groups. Each group viewed a set of emotional images while inside an MRI scanner as we measured emotional brain activity.
Then, 12 hours later, they were placed back inside the MRI scanner and we presented those same images, while again measuring emotional brain activity. During these two sessions participants also rated how emotional they felt in response to each image.
Importantly, half of the participants viewed the images in the morning and again in the evening, being awake between the two viewings. The other half viewed the images in the evening and again the next morning after a full night of sleep.
Those who slept in between the two sessions reported a significant reduction in how emotional they felt in response to seeing those same images again. In addition, results of the MRI scans showed a large and significant reduction in activity in the amygdala, the emotional centre of the brain that creates painful feelings.
Moreover, there was a re-engagement of the rational prefrontal cortex of the brain after sleep that was helping maintain a dampening brake influence on emotional reactions.
In contrast, the deep emotional brain reactions in those who remained awake across the day without the chance to sleep remained just as strong and negative, if not more so, at the second viewing. Those participants also reported a similarly powerful re-experiencing of painful feelings.
Since we had recorded the sleep of each participant during the intervening night between the two test sessions, we could answer a follow-up question: is there something about the type or quality of sleep that an individual experiences that predicts how successful sleep is at accomplishing next-day emotional resolution?
As the theory predicted, it was the dreaming state of REM sleep — and specific patterns of electrical activity that reflected the drop in stress-related brain chemistry during the dream state — that determined the success of overnight therapy from one individual to the next.
It is not, therefore, time that heals all wounds, but instead time spent in dream sleep that provides emotional convalescence. To sleep, perchance to heal. Dreaming is emotional first aid.
Sleep, and specifically REM sleep, was clearly needed in order for us to heal emotional wounds. But was the act of dreaming during REM sleep, and even dreaming of those emotional events themselves, necessary to achieve resolution and keep our minds safe from the clutches of anxiety and depression?
This was the question that Dr Rosalind Cartwright at Rush University in Chicago elegantly dismantled.
She decided to study the dreams of people who were showing signs of depression as a consequence of incredibly difficult emotional experiences, such as devastating breakups and bitter divorces.
Right around the time of the emotional trauma, she started collecting their nightly dream reports and sifted through, hunting for signs of the same emotional themes emerging in their dream lives.
She then performed follow-up assessments up to one year later to find out whether the patients’ depression and anxiety were resolved or persisted. She found that patients who expressly dreamed about the painful experiences soon after the events who went on to gain ‘resolution’ from their despair, mentally recovering a year later.
But those who did not dream of the painful experience itself could not get past the event and still being dragged down by a strong undercurrent of depression.
Cartwright had shown that it was not enough to have REM sleep, or even generic dreaming, when it comes to resolving our emotional past. Instead, we require REM sleep with a very specific kind of dreaming: which expressly involves dreaming about the emotional themes and sentiments of the difficulties we experience when we are awake.
In other words, it was only that content-specific form of dreaming that allowed these patients to move forward and not be enslaved by that traumatic past.
Just when I thought REM sleep had revealed all it could offer to our mental health, we discovered a second emotional brain advantage gifted by REM sleep — one that is arguably even more essential to survival.
Facial expressions represent one of the most important signals in our environment. They communicate intent of an individual and influence our behaviour in return.
There are regions of your brain whose job it is to read and decode the value and meaning of emotional signals, especially faces. And it is that very same essential network of brain regions that REM sleep recalibrates at night.
Deprive an individual of their REM-sleep dreaming state, and the emotional tuning of the brain loses its razor-sharp precision. A dream-starved brain cannot accurately decode facial expressions, which become distorted. You begin to mistake friends for foes.
We made this discovery by doing the following. Participants came into my sleep centre and had a full night of sleep. The following morning, we showed them many pictures of an individual’s face.
Each image was subtly different.
Participants viewed the faces in a random fashion while we scanned their brains in an MRI machine, and they rated how approachable or threatening the images were.
Having had a full night of sleep their brains had no problem deftly separating one emotion from another. But when those same participants were deprived of sleep, including REM sleep, they could no longer distinguish one emotion from another with accuracy. The sleep-deprived participants slipped into a default of fear, believing that even gentle or somewhat friendly faces were menacing.
The outside world had become a more threatening place — untruthfully so.
By removing REM sleep, we had, quite literally, removed participants’ level-headed ability to read the social world around them.
Now think of occupations that require individuals to be sleep-deprived, such as military personnel, doctors, nurses, and those in the emergency services — not to mention the ultimate caretaking job: new parents.
Without REM sleep and its ability to reset the brain’s emotional compass, those same individuals will be inaccurate in their social and emotional comprehension of the world around them, leading to inappropriate decisions and actions that may have grave consequences.
Adapted from Why We Sleep: The New Science Of Sleep And Dreams by Matthew Walker, published by Penguin Books at £9.99. © Matthew Walker 2018. To buy a copy for £7.99 (20 per cent discount), call 0844 571 0640 or go to mailshop.co.uk/books. P&P is free on orders over £15. Offer valid until August 11, 2018.