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For millennia, people have been fascinated by dreams.
“What a weird and wondrous experience it is that we get thrown into these virtual worlds where we meet people, we interact with them, where we can feel all kinds of emotions,” Antonio Zadra, a sleep and dream researcher at the University of Montreal, framed it in a recent interview.
Today, researchers continue to look for answers to how and why we dream, as growing evidence links dreaming to our health.
In the late 1800s, scientists began to interrogate the neurological basis of dreams. In 1893, psychologist Mary Calkins led a sleep study by candlelight, rousing the participants — one man, one woman — throughout the night to ask whether they were dreaming and to describe the vividness of their dreams.
From Calkins to Freud
Calkins was the first to quantify elements and timing of dreams.
She found that dreams generally took place in the present, and “when the dream was of the childhood’s home, or of some person who had not been seen for many years, the apparent age of the dreamer was never lessened to avoid anachronism. … It is thus evident that the dream is connected with the waking life, and — in the experience of these observers — usually with the recent life.”
But shortly after Calkins’s work, interest shifted to what dreams meant, Zadra said, at least in part because of Sigmund Freud.
Starting around 1900, the founder of psychoanalysis presented dreaming in the context of repressed desires. Freud wrote, for instance, that some anxiety dreams originate “in psychosexual excitation, in which case, the anxiety corresponds to repressed libido.” And, if someone dreamed of a still-living family member dying, Freud believed “the dreamer has wished them dead at some time or other during his childhood.”
Interest shifted back with the 1953 discovery of rapid eye movement (REM) sleep and the subsequent observation that when people are awakened from REM, they often have vivid dream recall. Research since then has shown that dreaming can happen during many stages of sleep. Even people who have brain lesions or take medications that all but eliminate REM still dream.
A wandering mind
Although certain electrical activity patterns in the brain have been linked to the presence or absence of dreaming, there is still no definitive biomarker signaling that a person is dreaming. Over the past decade, increased attention has been paid to the default mode network — a group of brain regions that become active when a person’s mind wanders, for example, while gazing out a window.
“Many of the more recent models of why we dream are tied into dreams as an intensified form of mind wandering,” Zadra said. But why we dream is still a point of contention in the field.
One long-held hypothesis is that dreaming serves as a means of simulating potential threats, preparing us for danger that may come our way.
“But many, many dreams have no physical or psychological threats,” Zadra countered. He said he thinks we dream to make sense of our waking experiences in the context of our past, drawing in loosely associated connections — something the default mode network allows us to do.
“When you wake up, things have been integrated into your understanding of yourself, of the world, your place in it, in bizarre, unrelated ways,” he said. “And what does that help you do? It helps you predict, or better, adapt to what lies ahead.”
Emotional processing
Another leading explanation is that it helps us process and regulate our emotions.
Sara Mednick, a cognitive scientist at the University of California at Irvine, said she views dreams as a “safe space where we can bring up potentially emotionally charged experiences,” and then play out the possibilities. “What you see is increases in arousal during dreams, but then you also see a calming down of that arousal system during the dream time,” she said.
In her research, Mednick has found that, for people who have experienced a negative emotional event, dreaming about it can help tamp down the attached emotions.
“If you dream about an event, you will retain detailed memory for that event, but you will also, across time, have less of an emotional arousal when you think about that event,” she said.
Mednick also views dreams as a kind of “overnight therapy,” citing a sleep study that found, among divorced people, those who dreamed about their ex-spouses had fewer depressive symptoms after one year. It illustrates that dreaming can have “nice long-term implications for having a healthy relationship with your emotional past,” she said.
Insights from dreaming
But some people go through life never remembering a dream. In sleep studies where participants are roused every five minutes throughout the night, they might report having dozens of dreams, and so a person who experiences micro-awakenings throughout the night might recollect more of their dreams.
Interest in a dream can also influence whether you remember it, said Zadra, as can waking up without an alarm.
“If you wake up naturally, then there’s a higher chance that you will wake up from REM sleep,” said Jing Zhang, a cognitive scientist at Harvard Medical School and Massachusetts General Hospital. Waking up during REM increases your odds of being in the midst of a dream. Zhang suggested writing down dreams you remember as soon as you wake up, as studies show that doing so improves dream recall.
Dreams can provide insight into a person’s well-being.
People who are more stressed or anxious “have more negative dreams and more negative dream content,” Zadra said. “They have more aggressive interactions in the dreams than friendly interactions. They have more hostilities, they have more failures than success. But as a person’s well-being improves, there are corresponding changes in their dream content.”
“A lot of [people with] mood disorders — depression, anxiety, PTSD — they report different patterns of dreaming, where they have excessive dreams,” which may be the result of prolonged REM, said Zhang, who is starting to investigate the role of dreaming in psychiatric populations, particularly people with schizophrenia.
If someone with PTSD is experiencing nightmares on replay, “they have a worse prognosis in terms of PTSD symptoms. It’s an indication that the system isn’t adapting as well as it could,” Zadra said. But this can be reframed as an opportunity for someone to seek help. “They need therapy, they need medication, they need something,” he added.