My insomniac nights are rare these days—but I had one last week. Nearing bedtime, it felt like a train was running through my body with the horn at full blast.
Earlier that evening I’d returned to a place where I had a humiliating experience a few years ago. Being at that place made it feel like the incident was happening again. The emotions it recalled were so powerful that at midnight I was still too aroused to fall asleep. I had a bad night and woke up to what I call an “insomniac day”: the feeling of being depressed and anxious at the same time.
Insomnia is often described as a problem of “hyperarousal,” and when I look for signs of hyperarousal in myself, this sort of situation comes to mind. It starts with a powerful emotion (like humiliation or excitement) and with what I’ve come to feel is an impaired ability to calm down. I have coping strategies that work pretty well in the daytime. But if something triggers strong emotion in the evening, I’m sunk.
The mechanisms underlying hyperarousal are still unknown. But according to a study recently published in the journal PNAS, it may be linked to fragmented REM sleep and unresolved emotional distress. Here’s more:
Sleep Helps Regulate Emotion
Sound sleep helps stabilize emotional memories in long-term memory. It also reduces their emotional charge. Being robbed at gunpoint just 2 blocks from your house is a frightening experience. But if you sleep well that night, the next day, although you’ll recall the robbery clearly, the fear accompanying it will be less distressing than it was the day before.
Rapid eye movement (REM) sleep, associated with dreaming, plays an important part in this process. Intact REM sleep enables us to regulate negative emotion and wake up in a better frame of mind. But when REM sleep is fragmented, as often occurs in insomnia, less resolution of emotional memories can occur. In this study, scientists looked for relationships between fragmented REM sleep, slow-resolving emotional distress, hyperarousal, and insomnia.
Shame and Other Self-Conscious Emotions
In the past, scientists investigating REM sleep’s role in emotion regulation have looked at its effects on basic emotions like fear and anger. But the authors of this study claim that people more often need help with problems involving self-conscious emotions such as pride, guilt, embarrassment, humiliation, and shame.
In this study, they focus on shame because “it may interfere the most with healthy psychological functioning. . . . By obstructing effective coping mechanisms, shame often hinders therapeutic progress, to the point that it may even lead to a negative therapeutic outcome.”
A Two-Part Study
Thirty-two people participated in the first part of the study, 16 with insomnia disorder and 16 with normal sleep. They spent two nights in a sleep lab undergoing polysomnography, a test that records brain waves. They also filled out a questionnaire about the frequency and content of their dreams.
Participants whose brain waves indicated more frequent arousals and who experienced increased eye movement during REM sleep (i.e., the insomnia sufferers) experienced more thought-like (rather than dream-like) mental activity at night. Investigators concluded that a higher “nocturnal mentation” score could be used as a stand-in for the experience of restless REM sleep.
For Part 2, about 1,200 participants in the Netherlands Sleep Registry filled out a battery of questionnaires concerning nocturnal mentation, the duration of emotional distress after a shameful experience, insomnia severity, hyperarousal, and a host of related phenomena.
Hyperarousal Linked to Slow-Dissolving Distress
The researchers analyzed their data using sophisticated statistical techniques and here’s what they concluded:
- The overnight resolution of distress from shame (and likely other negative emotions) is compromised in people with insomnia
- This deficit may result from a build-up of unprocessed emotion and contribute to hyperarousal
- This deficit seems in part to develop due to restless REM sleep (with frequent arousals and high-density eye movements) and thought-like nocturnal mentation.
If all this is true, then insomnia treatments need to target restless REM sleep. No treatment available now has been specifically shown to do that. Still, given that cognitive behavioral therapy for insomnia (CBT-I) has been shown to help people with insomnia and depression, another disorder characterized by irregularities in REM sleep, it might be the best treatment on offer now.