Insomnia and Emotional Memories Linked

Situations like being bullied at school, getting fired from a job or losing your train of thought during an important speech can feel mortifying when they occur. But in time, and with the help of sleep, the shame and embarrassment fade away. You can recall the experience without re-experiencing the emotional charge. This may not be the case for people with insomnia, results of a new study in the journal Brain suggest. Insomnia may involve disruption of the brain’s processing of emotional experience, burdening poor sleepers with emotionally charged memories. Here’s more about it.

Situations like being bullied at school, getting fired from a job or losing your train of thought during an important speech can feel mortifying when they occur. But in time, and with the help of sleep, the shame and embarrassment fade away. You can recall the experience without re-experiencing the emotional charge.

This may not be the case for people with insomnia, results of a new study in the journal Brain suggest. Insomnia may involve disruption of the brain’s processing of emotional experience, burdening poor sleepers with emotionally charged memories. Here’s more about it.

Biological Aspects of Insomnia

Insomnia used to be blamed mainly on bad habits and faulty thinking, but increasing attention is being paid to biological factors that underlie insomnia. Results of gene studies point to genetic factors that make people vulnerable to insomnia. Many insomnia risk genes are located in the limbic area of the brain, where the processing of emotion occurs. The possibility that insomnia has to do with disturbed emotion processing is what researchers in The Netherlands set out to investigate.

Past research has established a few things:

  • When people experience a novel emotional event, such being shown graphic photos of war victims, functional MRIs (similar to movies showing activity in the brain) show strong evidence of activity in the limbic system. However, recall of those photos at a later time does not involve limbic activity.
  • People with insomnia do not experience the same overnight resolution of emotional distress as normal sleepers do. In fact, studies conducted by Rick Wassing and colleagues showed that in insomniacs, emotional distress resulting from an unpleasant situation could linger for over a week.

A Working Hypothesis

People with insomnia are prone to fragmented sleep (particularly, fragmented REM sleep). It could be that in insomnia, an area or areas of the brain that typically go offline during sleep are not fully deactivated, resulting in continuing secretion of neurochemicals associated with alertness. One consequence could be the storage of long-term emotional memories that still retain ties to the limbic system and hence their emotional charge.

The research team decided to investigate the responses of normal sleepers and insomnia sufferers to novel emotional experiences and memories of past emotional experiences and then compare them. Their hypothesis was that in people with insomnia, brain activity during recall of distant emotional events would look more like brain activity during novel emotional events than in normal sleepers.

Preparing for the Study

Fifty-seven people participated, aged 18 to 70 years. Twenty-seven participants had a diagnosis of insomnia disorder and 30 were classified as normal sleepers.

At an intake interview participants shared information about shameful experiences they could recall from their past. Each participant also underwent a structural MRI brain scan and made a karaoke-style audio recording in which he/she sang along to a familiar tune.

A week later testing began. Throughout the testing, each participant was wired with electrodes to assess galvanic skin response (changes in sweat gland activity that would reflect the intensity of the participant’s emotional state) and was undergoing functional MRI that would capture and record activity in the brain.

An Ingenious Test of Emotional Intensity

There were two tests, the first involving measurement of participants’ reactions to a novel shameful experience. Participants in both groups, the insomnia sufferers and the normal sleepers, were told they would be exposed to recordings of their own singing and the singing of others, and that two researchers would be listening in. Then each participant had to listen to 16-second fragments of their own solo singing, unaccompanied by music. The fragments were intermixed with neutral stimuli consisting of fragments of the same song sung by a semi-professional singer. How’s that for a novel shaming experience!

The second test involved recall of five shameful events from the distant past. For 16 seconds participants were asked to remember each shameful experience. In between each shameful experience, participants were asked to recall a trivial non-emotional experience from the past. After recounting each memory, participants rated its emotional intensity.

What the Research Team Discovered

Analyzing the data, researchers found, predictably, that emotional stimuli were on average rated as more intense than neutral stimuli. In addition, data from subjective participant reports and assessment of galvanic skin response showed the following:

  • The response to novel neutral and novel emotional experiences was similar in people with insomnia disorder and normal sleepers
  • Normal sleepers’ response to remembered shameful events was similar to their response to remembered neutral events (i.e., the emotional charge that accompanied the original experience was gone).
  • People with insomnia, however, had a stronger response to relived shameful memories than to neutral memories (suggesting continuing involvement of the limbic system).

Movies of the Brain Are Confirmatory

From the functional MRIs, investigators found the following:

  • The shame participants felt as they listened to their own singing triggered intense limbic activity in the brains of both normal sleepers and people with insomnia
  • Although memories of past shameful experiences did not induce a limbic response in normal sleepers, in insomnia sufferers, they did. In fact, in the brains of people with insomnia, limbic activity was noted in many of the same areas active during novel emotional experiences, notably, the anterior cingulate cortex.

“The findings,” write the authors, “suggest that normal sleepers activate a markedly different brain circuit while reliving emotional memories from the distant past as compared to when they are exposed to novel emotional experiences. In patients with insomnia, however, the brain circuits recruited with reliving distant emotional memories overlapped with the circuits recruited during a novel emotional experience.”

The restless REM sleep that often characterizes insomnia may be attributable to a failure to deactivate a part of the brain that, if shut down, could enable more restorative sleep and quicker recovery from emotionally painful experiences. There are ways to treat insomnia behaviorally, and some work pretty well. But only when more research into the causes of insomnia is conducted will researchers be able to find a cure.

Do the findings of these researchers ring as true to you as they do to me?

Why Are Insomniacs Prone to Hyperarousal?

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.

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:

hyperarousal is a common daytime symptom of insomniaMy 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.

Restless REM Sleep May Lead to Hyperarousal

Do you tend to dwell on upsetting thoughts? Does your arousal thermostat feel like it’s set too high, making it hard for your body to relax and fall or stay asleep? Insomnia is often described as a disorder of hyperarousal, yet how and why the hyperarousal develops is unclear.

Now a team of 13 sleep scientists from three countries have taken findings from different lines of research, conducted a study of their own, and come up with a plausible explanation for why our minds and bodies feel like they’re stuck in overdrive and just can’t stop. Here’s what may lie behind our trouble falling and staying asleep.

insomnia, characterized by fragmented REM sleep, leads to slow emotional processingDo you tend to dwell on upsetting thoughts? Does your arousal thermostat feel like it’s set too high, making it hard for your body to relax and fall or stay asleep? Insomnia is often described as a disorder of hyperarousal, yet how and why the hyperarousal develops is unclear.

Now 13 sleep scientists from three countries have taken findings from different lines of research, conducted a study of their own, and come up with a plausible explanation for why our minds and bodies feel like they’re stuck in overdrive and just can’t stop. Here’s what may lie behind our trouble falling and staying asleep.

Two Kinds of Sleep

Whether we sleep poorly or well, our nights are composed of two kinds of sleep: REM sleep, when most dreaming occurs and when the eyes move rapidly from side to side; and non-REM, or quiet, sleep. The deepest stage of non-REM sleep is called slow-wave sleep.

In the past, scientists thought that insomnia probably had to do with a dysfunction related to slow-wave sleep or some other feature of non-REM sleep. This may be the case for some people with insomnia.

But the results of two recent studies suggest that the problem may lie elsewhere. The findings show that sleep maintenance insomnia (the type of insomnia involving middle-of-the-night awakenings) is characterized by fragmented REM sleep.

Importance of REM Sleep

There’s solid evidence now that REM sleep—most of which occurs in the second half of the night—helps us process negative emotions such as fear and anger and self-conscious emotions such as guilt, embarrassment, humiliation, and shame. In studies where participants are forced to rise too early, they often wake up in a bad mood.

The reason is that they’ve gotten insufficient REM sleep, say sleep scientists, and the full processing of emotion has not had a chance to occur. As a result, any negative emotion they experienced the previous day may still retain its emotional charge.

There’s also preliminary evidence that fragmented REM sleep (such as that found in insomnia) hinders the overnight resolution of emotional distress.

Authors of the current study, published in Proceedings of the National Academy of Sciences, wanted to take this research further. They predicted that fragmented (or restless) REM sleep could interfere with the overnight resolution of emotional distress, thus contributing to the accumulation of arousal, and eventually hyperarousal, associated with insomnia.

A Two-Part Study

First, the researchers tested 32 people—16 with insomnia disorder and 16 normal sleepers—in a sleep lab for two nights. The object was to find out if restless REM sleep correlated with the frequency of participants experiencing thought-like rather than dream-like mental activity at night (as assessed by questionnaires). Thought-like nocturnal mentation—when we’re mentally chewing on a problem, for example—is specifically associated with restless REM sleep.

In addition, the researchers looked for relationships between restless REM sleep, duration of emotional distress, and chronic hyperarousal in data compiled on 1,199 people participating in the Netherlands Sleep Registry. The NSR is a psychometric database created to facilitate research on factors that discriminate people with insomnia from people without sleep complaints.

Restless REM Sleep, Emotional Distress, Hyperarousal

The investigators used sophisticated statistical methods to analyze their data, and here’s what they found:

  • Compared with normal sleepers, insomniacs were slower to recover from long-lasting emotional distress. The more severe the insomnia, the slower the recovery.
  • Thought-like mental activity was more frequent among insomniacs than normal sleepers, and it was significantly associated with emotional distress lasting overnight (but not with short-lasting distress resolved during the previous day).
  • The more severe the insomnia, the more people reported symptoms of hyperarousal.
  • Long-lasting emotional distress accounted for 62.4% of the association between hyperarousal and the thought-like mental activity occurring during restless REM sleep.

What It Means for Us

The findings conformed to researchers’ expectations. So here’s their explanation for why insomniacs, both mentally and physiologically, keep going and going and can’t seem to relax into sound, consolidated sleep: mental activity we experience at night—which is associated with fragmented REM sleep (and increased eye movement density)—interferes with the overnight resolution of emotional distress. So we awaken with the distress still in place, which ramps up arousal. Over time, this could lead to a state of chronic hyperarousal.

It sounds plausible to me. Your thoughts?