Thoughts in bed, normal sleep onset, and insomnia
Alexandre Lemyre, M.A., Ph.D.
The content of this article was last updated on February 1, 2022.
Introduction
During my doctoral studies, I did a four-month research internship in Vancouver, Canada. The goal of this internship was to learn and theorize about the role of cognitive activity (mental activity) in insomnia. I ended up working on a review of the scientific literature in which we summarized much of what had been written on this topic. This literature review was eventually published in an influential scientific journal specialized in sleep research (Lemyre et al., 2020). I am eager to share with you some of the things we have learned.
Cognitive activity during normal sleep onset
Before I address what is going through someone’s mind when they experience insomnia, it is worth discussing what happens when sleep onset does occur. Contrary to what many people might believe, sleep onset is not like turning a switch off. Instead, it is a gradual transition from quiet/calm wakefulness to light sleep (called sleep stage 2) or rapid eye movement sleep (REM sleep) that can last for a few minutes. For this reason, sleep onset is called “sleep stage 1”.
What happens in your mind during this transition toward sleep? Until now (and probably for a long time to come), there has only been one way to answer this question: to wake up a person during sleep onset (sleep stage 1) and ask them: (a) what was going through their mind just before they were awakened, and/or (b) specific questions on their mental activity before being awakened. One limitation of this approach is that the participant may not always remember (clearly, or at all) what they were thinking before being awakened.
To determine whether a person is awake, undergoing sleep onset (sleep stage 1), or in any other sleep stages (stage 2, stage 3, or REM sleep), several indicators can be used. This includes brain waves (measured with an electroencephalogram, or EEG), eye movements, and body movements. Measuring these indicators requires specialized equipment and is, therefore, usually performed in a sleep laboratory. A sleep laboratory includes a sound‑proof and darkened sleeping room with the sleep monitoring equipment. In another room, sleep technicians can track the person’s sleep in real time and awake them from the specific sleep stages (for instance, sleep stage 1). As an alternative to sleep laboratories, some researchers have used the Nightcap, which is an ambulatory sleep monitoring device that is used at home. The Nightcap automatically identifies sleep onset based on algorithms and sends a signal to awaken the person. Notwithstanding whether the study is conducted in a sleep laboratory or with the Nightcap, the participant’s description of their mental activity prior to being awakened is recorded and subsequently analyzed by the researchers. The following subsections present a summary of the findings from several studies that have been conducted in a sleep laboratory (Foulkes et al., 1966; Foulkes & Vogel, 1965; Hori et al., 1994; Michida et al., 2005; Molinari & Foulkes, 1969; Vogel et al., 1972; Wackermann et al., 2002; Yang et al., 2010) or using the Nightcap (Fosse et al., 2001; Rowley et al., 1998; Speth et al., 2016).
Sensory imagery. Most of the time, sleep onset is not just “thought-like”: it contains sensory imagery. I would like to provide precise estimates of the frequency at which each type of imagery occurs, but unfortunately, results tend to vary between studies, which might be due to methodological differences. What is clear, however, is that the most frequent form of imagery is visual (e.g., imagining people or objects), followed by auditive imagery (i.e., sounds, such as voices) and bodily/tactile imagery.
Hallucinations. The term “hallucination” means that during sleep onset, the person often thinks that they are witnessing- or taking part in events of the real world (just like in a dream, when you think that what you perceive is actually happening). This means that the person is no longer aware of their actual environment, or that they are currently lying in their bed. Furthermore, when you imagine things in waking, you are aware that you are creating those events in your mind; on the contrary, during sleep onset, the imagined events can appear to be uncontrollable (here again, there is an evident parallel to be made with dreams). The further you progress into sleep onset (i.e., the closer you get to sleep), the more likely your mental experiences are to be “hallucinatory”.
Cognitive abilities. Our capacity to think soundly tends to decrease during sleep onset. This includes control over our thinking generally, but also specific cognitive processes such as recognizing, interpreting, comparing, explaining, planning, and so forth. Moreover, as we fall asleep, our thoughts are decreasingly oriented toward the future.
Pre-sleep thoughts in individuals with insomnia
In two studies (Harvey & Espie, 2004; Wicklow & Espie, 2000), individuals with insomnia (mostly university students) were asked to record what was going through their mind when having difficulty falling asleep. To do so, they were provided with a voice-activated tape recorder. It is worth highlighting that most of the reported thoughts likely occurred during quiet wakefulness while lying in bed rather than during sleep onset (i.e., sleep stage 1). The thoughts that were reported by the participants were categorized as follows:
(1) Rehearsing/planning and problem‑solving: thinking about past experiences, forthcoming events, things to do, work-related and social issues.
- 43% of the reported thoughts in the study by Wicklow and Espie (2000)
- 32% of the reported thoughts in the study by Harvey and Espie (2004)
(2) Sleep and its consequences: thinking about the need or desire to sleep, the importance of sleeping.
- 20% of the reported thoughts in the study by Wicklow and Espie (2000)
- 21% of the reported thoughts in the study by Harvey and Espie (2004)
(3) Reflection on the quality of thoughts: thinking about one’s own thinking.
- 12% of the reported thoughts in the study by Wicklow and Espie (2000)
- 11% of the reported thoughts in the study by Harvey and Espie (2004)
(4) Arousal status: thinking about a feeling of exhaustion, sleepiness, or physical tiredness.
- 9% of the reported thoughts in the study by Wicklow and Espie (2000)
- 7% of the reported thoughts in the study by Harvey and Espie (2004)
(5) Autonomic experiences: thinking about one’s heart rate, headache, tension, etc.
- 6% of the reported thoughts in the study by Wicklow and Espie (2000)
- 15% of the reported thoughts in the study by Harvey and Espie (2004)
(6) External noises.
- 6% of the reported thoughts in the study by Wicklow and Espie (2000)
- 5% of the reported thoughts in the study by Harvey and Espie (2004)
(7) Rising from the bed: thinking about getting up.
- 1% of the reported thoughts in the study by Wicklow and Espie (2000)
- 7% of the reported thoughts in the study by Harvey and Espie (2004)
Wicklow and Espie (2000) observed that three categories of thoughts were associated with a longer sleep onset latency (i.e., a longer time to fall asleep) during the period of the study, which lasted three days: rehearsing/planning and problem-solving, sleep and its consequences, and autonomic experiences.
Questionnaires measuring pre-sleep cognitive activity: links with insomnia
In the previous sections, I focused on studies in which the participants reported their own mental activity in real time, that is, when they were awoken from sleep onset (sleep stage 1) or when they found themselves incapable of falling asleep (for the participants with insomnia). Another method to assess pre-sleep mental activity is to use questionnaires. Questionnaires can usually be completed at any time and require relatively little involvement from the participants. The use of questionnaires has a downside, however, since it relies on the participants’ capacity to accurately recall the mental activity they usually experience while in bed.
A few questionnaires have been developed to assess variables (or “constructs”) related to pre-sleep mental activity. These questionnaires and the findings that have resulted from their use are presented in the next subsections. It is important to mention that all these findings are correlational in nature. Correlations do not demonstrate the existence of a causal relationship, nor do they inform on the direction of any existing causal relationship (i.e., whether A causes B and/or B causes A). Thus, any causal interpretation should be viewed as merely suggestive.
Mental overactivity and cognitive arousal
Pre-sleep “mental overactivity” and “cognitive arousal” are rather vague constructs that correspond to the intensity of mental activity during the pre-sleep period. Although they have different names, in my understanding, these two constructs are one and the same. Mental overactivity is evaluated by a subscale from the Sleep Disturbance Questionnaire (Espie et al., 2000; Espie et al., 1989), which contains three items: “my mind keeps turning things over”, “my thinking takes a long time to unwind”, and “I am unable to empty my mind”. Cognitive arousal is evaluated by a subscale from the Pre-sleep Arousal Scale (Nicassio et al., 1985) that contains eight items such as “being mentally alert, active” and “can’t shut off thoughts”. Not surprisingly, there is good evidence that pre-sleep mental overactivity is associated with insomnia (Ellis et al., 2002; Harvey, 2000; Harvey et al., 2002; Kohn & Espie, 2005), and there is excellent evidence that pre-sleep cognitive arousal is associated with insomnia (this evidence is reviewed in Lemyre et al., 2020).
Insomnia-related worries
Only one questionnaire has been developed specifically to evaluate insomnia-related worries during the pre-sleep period. This is the Worry Insomnia Questionnaire (Jansson & Linton, 2006), which evaluates worries about sleeplessness (three items), and worries about health (three items). Examples of items are “I worry about my sleep when I go to bed”, and “I worry that my body will be harmed if I sleep poorly”. Based on that single study, both types of worries are associated with a longer sleep onset latency (the time it takes to fall asleep) in individuals who have experienced insomnia for 7 to 12 months, but not in individuals who have experienced insomnia for 3-7 months (Jansson & Linton, 2006). This result suggests that insomnia-related worries may contribute to maintain the insomnia problem, but only after insomnia has been present for several months.
Regrets or rumination
Regrets and/or rumination at bedtime have been evaluated by two questionnaires. The Bedtime Counterfactual Processing Questionnaire (Schmidt & Van der Linden, 2009) contains items such as “After going to bed, how often do you feel guilty because you have the impression of having done wrong to others?”, whereas the Nocturnal Regret Questionnaire (Schmidt et al., 2011) contains items such as “After going to bed in the evening, it happens that I regret things that I have done”. In studies conducted with undergraduate students (Schmidt et al., 2018; Schmidt & Van der Linden, 2009, 2011, 2013) and elderlies (Schmidt et al., 2011), regrets/rumination were positively associated with the severity of insomnia symptoms. Insomnia symptoms were measured by the Insomnia severity Index (Bastien et al., 2001), which evaluates the following: (a) the severity of the insomnia problem (difficulty falling asleep, difficulty staying asleep, and problem waking up too early), (b) the degree of satisfaction/dissatisfaction with sleep, (c) the interference of the sleep problem with daily functioning, (d) how noticeable the sleep problem is to others, and (e) the degree of worry/distress about the sleep problem.
Thought control strategies
The Thought-control Questionnaire Insomnia – revised version (Ree et al., 2005; Schmidt et al., 2009) evaluates the use of 35 strategies to control or deal with one’s own thoughts while trying to sleep. These strategies are divided in six categories, of which four correspond to cognitive strategies. These cognitive strategies are : (a) aggressive suppression (e.g., “I tell myself not to be so stupid”, “I try to push the thoughts out of my head”, “I punish myself for having the thought”), (b) worry (e.g., “I worry about more minor things”, “I dwell on other worries”, “I think about past worries instead”), (c) reappraisal (e.g., “I analyze the thought rationally”, “I try to reinterpret the thought”, “I question the reasons for having the thought”), and (d) cognitive distraction (e.g., “I think pleasant thoughts instead”, “I call to mind positive images instead”, “I let my mind go blank”). Studies with undergraduate students and senior high-school students have found that the first three cognitive strategies – aggressive suppression, worry, and reappraisal – are positively associated with a difficulty falling asleep and with insomnia symptoms more generally (as assessed by the Insomnia Severity Index) (Gellis & Park, 2013; Kallestad et al., 2010; Schmidt et al., 2010; Schmidt et al., 2009). Likewise, individuals with insomnia score higher on the subscales measuring these three strategies compared with good sleepers (Ree et al., 2005). Besides, one study conducted with college students reports that the strategy of cognitive distraction is negatively associated with insomnia symptoms (Gellis & Park, 2013). These results suggest that the type of mental strategies that are used in reaction to one’s own thoughts may influence the time required to fall asleep.
Monitoring
The Sleep Associated Monitoring Index (Semler & Harvey, 2004) contains eight categories, of which three refer to monitoring during the pre-sleep period: pre-sleep monitoring for body sensations consistent with falling asleep (e.g., “your muscles getting weaker or relaxing”), pre-sleep monitoring for body sensations inconsistent with falling asleep (e.g., “feelings of tension or discomfort within your body”), and pre-sleep monitoring of the environment (e.g., “noises in the house”). Compared with good sleepers, poor sleepers score higher on each of these three subscales (Semler & Harvey, 2004). This result suggests that monitoring one’s own sensations or the environment may delay sleep onset.
Interviews on pre-sleep cognitive activity
Two studies used interviews to assess pre-sleep mental activity (Harvey, 2000; Nelson & Harvey, 2003). Harvey (2000) interviewed individuals with insomnia and good sleepers. One section of the interview assessed the experience of pre-sleep thoughts in the form of images, which is different from pre-sleep verbal thoughts (i.e., thoughts in the form of language). About two thirds of the participants in each group reported experiencing thoughts in the form of images on a typical night. These images were perceived as more distressing by individuals with insomnia compared to good sleepers (Harvey, 2000). Furthermore, Nelson and Harvey (2003) interviewed individuals with insomnia and good sleepers after a nap period. One section of the interview focused on the thoughts (i.e., thoughts in the form of images and verbal thoughts) that were experienced prior to falling asleep. Individuals with insomnia perceived the images and the verbal thoughts as being more distressing compared with good sleepers (Nelson & Harvey, 2003).
Experimental studies testing the relationship between worries and insomnia
Two studies (Gross & Borkovec, 1982; Tang & Harvey, 2004) used a “speech threat” to evaluate the effect of worries on sleep onset latency (i.e., the time it takes to fall asleep) in individuals who are good sleepers. Participants in the experimental group were told that they would have to give a short speech after a nap (the topic of the speech was not specified). Presumably, the prospect of giving a speech would trigger worry-related processes, which in turn would delay sleep onset. The participants in the control group were not told they would have to give a speech after the nap period. As expected, the participants in the experimental group took longer to fall asleep on average compared with the participants in the control group (Gross & Borkovec, 1982; Tang & Harvey, 2004).
In a third study (Nelson & Harvey, 2002), individuals with insomnia were given an envelope that had to be opened just before turning off the light (the participants slept at home). The letter in the envelope informed the participants that they would give a speech in front of a small audience on the next day (the letter did not specify the topic of the speech). For the first group, the letter contained the instruction to think about the incoming speech in the form or images (pictures or scenes) for six minutes. For the second group, the letter contained the instruction to think about the incoming speech in the form of verbal thoughts for six minutes. The results showed that thinking about the incoming speech in the form of images generated more immediate distress and arousal, but also a shorter sleep onset latency (that is, less time required to fall asleep) and less anxiety toward the prospect of giving a speech on the following morning. The authors of the study suggested that thinking about a worry (in this case, the incoming speech) in the form of images might facilitate emotional processing, and consequently, promote a faster transition from wakefulness to sleep (Nelson & Harvey, 2002).
In a fourth study (Carney & Waters, 2006), individuals with insomnia were divided into two groups. The first group had to engage in “constructive worry” during the evening. More precisely, they had to identify at least three problems/worries that were susceptible to keep them awake on that night, then identify the next step that could contribute to the resolution each worry. The second group (which served as a comparison group) only had to list three or more worries that they had experienced during the day. The two groups took a similar time to fall asleep on that night; however, the “constructive worry” group spent less time awake during the night and experienced less cognitive arousal in bed (Carney & Waters, 2006). Overall, these results do not support the effectiveness of a “constructive worry procedure” in facilitating sleep onset.
Summary and Conclusion
Sleep onset is a gradual transition from quiet wakefulness to light sleep or REM sleep. It often involves visual, auditive, and/or bodily (e.g., tactile) imagery, a loss of awareness of one’s own environment (being in a bed, in a bedroom), and altered cognitive abilities. When having difficulty falling asleep, individuals with insomnia most commonly think about rehearsing/planning and problem‑solving, as well as sleep and its consequences. Studies using questionnaires have shown that several thought processes are linked with insomnia, including cognitive arousal (or mental overactivity), insomnia-related worries, regrets and rumination, certain thought control strategies (aggressive suppression, worry, and reappraisal), and monitoring bodily sensations or environmental stimuli (such as ambient noises). Relatedly, studies using interviews found that individuals with insomnia experience more distressing thoughts during the pre-sleep period. Finally, experimental studies confirmed that worries can delay sleep onset. Interestingly, the mode of thinking about one’s own worries (in the form of images or in a verbal form) might influence the extent to which these worries interfere with sleep.
The most interesting conclusion from our review on pre-sleep cognitive activity (Lemyre et al., 2020) is that both normal transition to sleep and insomnia involve cognitive activity, that is, thoughts and mental images. Thus, it is not cognitive activity per se that delays sleep onset (i.e., that causes insomnia), but the type of cognitive activity. My hypothesis is that emotionally charged cognitive activity in bed delays sleep onset because it signals the presence of threats or rewards. In an evolutionary perspective, falling asleep in the presence of threats or rewards would have been deleterious for the fitness of our ancestors (i.e., their ability to survive and reproduce). Thus, it seems reasonable to hypothesize that the brain mechanisms controlling sleep and wakefulness (Brown et al., 2012) have evolved to ensure an adaptive balance between: (a) the benefits of sleep / the consequences of sleep deprivation, and (b) the need to be awake to avoid threats and to approach rewards. I have begun to explore this idea in the form of a formal theory. I believe that a better understanding of the “sleep onset control system” will be necessary to determine how certain thoughts in bed delay sleep onset, and more importantly, to develop better ways of coping with these unwanted thoughts.
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