Maybe it was your mom. Maybe your grandma. Maybe some other wise elder. But somewhere along the way, you've no doubt been given this piece of advice (especially if you're in a serious relationship): never go to bed angry.
The logic behind this recommendation is pretty easy to divine. Arguments and hurt feelings will fester if left unresolved. Plus, no one gets a good night's rest when they're brooding about unresolved issues anyway.
For these traditional, sensible reasons this has always been good advice, but it's even better advice now that science has investigated the psychological and brain processes underlying this oft-repeated relationship truism. Going to bed angry, a new study shows, really is a terrible idea, but not only for the reasons your mom gave you.
Sleep is super glue for your memory.
The research out of Beijing Normal University studied the effects of anger by asking 73 male volunteers to memorize pairs of faces and unsettling images, like injuries or crying children. What was the point of this unpleasant task? The study subjects were then asked how many of the pairings they recalled 30 minutes after the memorization session, compared to after sleeping through the night with the distressing images still percolating in their brains.
The results showed that, after sleeping on the images, the study subjects were significantly less able to repress thoughts of the unsettling pictures. A night's sleep, in other words, seems to strengthen our memories of negative emotions and events.
That's not a huge surprise as sleep has been shown to aid memory consolidation in general, but the researchers went a step further, investigating the brain basis for these findings with fMRI scans. These brain scans showed that immediately following being exposed to the pairs of images, the memories appeared to be concentrated in an area called the hippocampus. After a night's sleep, the memories had spread out more across the brain, making them presumably harder to root out.
While the research was aimed at eventually developing treatments for those suffering from PTSD, the study authors said these initial findings were also useful for those of us who just have to deal with normal negativity like marital spats and nasty work disagreements. And the recommendation is just what your mother would suggest (though for slightly different reasons).
"In our opinion, yes, there is certain merit in this age-old advice," Yunzhe Liu, the neuroscientists who who led the research, commented. "We would suggest to first resolve argument before going to bed; don't sleep on your anger."