Insomniacs tend to have a hard time getting past embarrassing mistakes, even when the stressful event occurred decades ago, according to a new study by researchers at the Netherlands Institute for Neuroscience.
The scientists asked participants to relive their most shameful experiences from decades ago while observing their brain activity with an MRI scan. They found that while good sleepers had settled those experiences in their head as neutralized memories, those with insomnia had not been able to do so.
The finding suggests that failure to neutralize emotional distress could be a major contributor to insomnia and may also help explain why insomnia is the primary risk factor for the development of disorders of mood, anxiety, and posttraumatic stress.
The findings are published in the scientific journal Brain.
Researchers have established that sleep helps us to remember important experiences. But sleep is also necessary to get rid of the emotional distress that may have occurred during those experiences. Both these overnight processes involve changes in the connections between brain cells: some become stronger and consolidate memories, whereas others are weakened and get rid of unwanted associations.
“Sayings like ‘sleeping on it’ to ‘get things off your mind’ reflect our nocturnal digestion of daytime experiences,” said doctoral student and first author Rick Wassing. “Brain research now shows that only good sleepers profit from sleep when it comes to shedding emotional tension. The process does not work well in people with insomnia. In fact, their restless nights can even make them feel worse.”
The new findings support a previous study conducted by the same research group. In this study, published in the journal Sleep, the researchers asked participants to sing along to a song karaoke-style. Headphones prevented participants from hearing their own voice and finding the correct pitch. Their singing was recorded and played back for them later.
Many participants felt intense shame when listening to their own out-of-tune solo singing. But when good sleepers listened to their own singing again after getting a good night’s sleep, they didn’t feel that distressed about it anymore. They had released the distress from their minds. However, after a restless night, people with insomnia became even more upset about their embarrassing experience.
The new findings suggest that insomnia triggers may actually be found in brain circuits that regulate emotions, rather than in brain regions that regulate sleep, as previously believed. These emotion-regulating circuits contain risk genes for insomnia and may not activate properly, as they normally do, during rapid eye movement sleep.
Without the benefits of sound sleep, distressing events of decades ago continue to activate the emotional circuits of the brain as if they are happening right now. This suggests that people with insomnia may continue to be haunted by memories of past distress.