Sleeping isn't just about refreshing us for the day ahead. It also has a more long-term impact on our health. The deep REM sleep associated with dreams actually shuts off our brain's stress chemistry and soothes our most painful memories.
That's the finding of researchers at UC Berkeley, who found a number of dramatic stress-related transformations take place in our brain when we enter REM sleep. Dreaming effectively functions as a way for the brain to process painful memories and systematically take the edge off them. While it obviously can't erase our traumas, it appears that such deep sleep does have some serious anti-stress benefits.
Researcher Matthew Walker explains:
"The dream stage of sleep, based on its unique neurochemical composition, provides us with a form of overnight therapy, a soothing balm that removes the sharp edges from the prior day's emotional experiences."
However, it appears that sufferers of post-traumatic stress disorder no longer fully benefit from this process. This may be because the psychological scars are so deep and can be so easily triggered by everyday events - say, a loud noise like a car backfiring - that the entire experience remains too visceral to be stripped away during REM sleep.
This research is some of our first clear insight into the emotional effects of REM sleep, which is a deep state of slumber in which we spend about a fifth of our time asleep. Indeed, any additional insight into why we sleep is good news - as much as we can identify all the bad things that happen to you if you don't sleep enough, it's surprisingly difficult to come up with a clear reason what purposes sleep serves.
Lead author Els van der Helm comments:
"During REM sleep, memories are being reactivated, put in perspective and connected and integrated, but in a state where stress neurochemicals are beneficially suppressed."
And Matthew Walker adds:
"We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress. By reprocessing previous emotional experiences in this neuro-chemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength. We feel better about them, we feel we can cope. This study can help explain the mysteries of why these medications help some PTSD patients and their symptoms as well as their sleep. It may also unlock new treatment avenues regarding sleep and mental illness."