Background The novel hypothesis of a recently proposed theoretical model is that chronic insomnia is maintained by a cascade of cognitive processes

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1 17 Background The novel hypothesis of a recently proposed theoretical model is that chronic insomnia is maintained by a cascade of cognitive processes operating during the night and the day (Harvey, 2002). The overarching goal of the research conducted, with the support of the ESRC, was to provide a detailed experimental investigation of one of the cognitive processes proposed by the model to be core to the maintenance of insomnia, namely: the role of distorted perception of sleep. It is noted that this cognitive process has been implicated in several other theoretical accounts of insomnia (e.g., Horne, 1989; Perlis et al., 1997). What is Insomnia? Insomnia is a complex disorder of heterogeneous aetiology that can include physical disorders, circadian rhythm disturbances, psychological factors, and poor sleep habits. Insomnia is the second most common psychological health problem and has serious consequences including functional impairment (difficulty completing daily tasks), work absenteeism, and increased use of medical services (Roth & Ancoli-Israel, 1999). The role of distorted perception. The insomnia literature presents a puzzle. On the one hand people with insomnia honestly and persistently report that they do not get enough sleep and that they suffer significant daytime impairment and fatigue. On the other hand, researchers have been unable to document consistent differences between the sleep obtained by patients with insomnia and the sleep obtained by good sleepers (see Chambers & Keller, 1993 for review). What could explain these puzzling results? One clue is the robust evidence that patients with insomnia overestimate their sleep onset latency and underestimate their total sleep time (e.g., Coates et al., 1982). Contrary to the assumption that this pattern is only found among patients with insomnia diagnosed with sleep state misperception, Edinger and Fins (1995) found that underestimation of total sleep time was marked in patients with a range of insomnia subtypes. In contrast, good sleepers typically estimate their sleep accurately (Bonnet & Arand, 1994). On the basis of these findings, a recently proposed cognitive model of insomnia suggests that one of the core processes maintaining insomnia is distorted perception of sleep (Harvey, 2002). It should be noted that distortions of reality are not unfamiliar to clinically orientated psychopathologists. People with depression see the world, themselves and the future as excessively negative. Socially phobic individuals think they come across in social situations less well than they actually do. When having a panic attack people with panic disorder are convinced they are going mad or having a heart attack. In the same way, it is proposed that insomnia is, at least partly, maintained by distorted perception of their sleep. Objectives The research conducted had two objectives: (1) to test the proposal that distorted perception of sleep functions to maintain insomnia and (2) to provide a test of two competing theories, detailed below, of the mechanism underpinning distorted perception of sleep. Overview of Methods The experiments that were conducted employed a variety of intersecting methods. Specifically, proof that a process of interest, let s call it X, is a cause of a disorder can be deduced by experimental manipulations that either (1) delete X in a group of patients with the disorder and observe whether the symptoms of the disorder improve or (2) introduce X to a sample without the disorder and observe whether this analogue sample move in to a state akin to the patients with the disorder. In the research conducted both methods were employed. Experiments 1 and 2 employed independent samples of patients with insomnia and conducted manipulations designed to alter the insomnia symptoms. Experiments 3 and 4 employed independent samples of good sleepers. Second, some studies were conducted within the natural home environment (Studies 1 and 2) whereas others, that require a tighter, more sensitive experimental procedure will be conducted in the sleep laboratory (Studies 3 and 4). Instrumentation Actigraphs were used as the objective sleep estimate. The actigraph (Ambulatory Monitoring Inc.) is a small wrist-watch like device worn continuously on the non-dominant wrist. 17

2 18 Embedded within is a miniaturized piezoelectric acceleration sensor that detects and stores information about physical motion. This is downloaded into compatible software to generate an estimation of the sleep/wake cycle. There is strong agreement, for adults without a sleep complaint, between the sleep estimates generated by actigraphy and polysomnographically measured sleep, the gold standard (above 90%; Jean-Louis et al., 2001). However, the agreement rate is lower in individuals who lie immobile for long periods (e.g., clinically depressed patients and insomnia patients) as the technology is less accurate in differentiating quiet pre-sleep wakefulness from sleep. Nonetheless, the advantages of using actigraphy are that 1) it is non-intrusive, 2) it allows sleep to be monitored in the participants own natural sleeping environment, 3) it is relatively inexpensive, and 4) actigraphic data is quickly downloaded and is presented in a clear and easily digestible manner such that participants can easily calculate how long it took them to fall asleep and how long they slept in total (needed for Experiment 1). Brief report on Experiment 1 This study aimed to provide evidence that distorted perception of sleep functions to maintain insomnia by attempting to correct distorted perception of sleep and observing the effects on symptomatology. It was predicted that the behavioural experiment designed to correct distorted perception of sleep should be associated with (1) more accurate subjective perception of sleep and (2) reduced sleep related anxiety and preoccupation. Method Design and Procedures Participants diagnosed with insomnia were randomly allocated to either the Shown- Discrepancy Group (n = 20) or the No-Demonstration Group (n = 20) and attended three sessions. Session one. After obtaining informed consent, the Insomnia Diagnostic Interview (IDI; Harvey et al., 2004) and the Structured Clinical Interview for Diagnosis (SCID; Spitzer et al.,1996) were administered. To index baseline distorted perception, the participants were given an actigraph and a sleep diary. They were instructed to wear the actigraph, on their non-dominant wrist, from two hours prior to bedtime until rising in the morning for the next three consecutive nights and to complete the sleep diary immediately on waking for the next three consecutive mornings (Days 1 to 3). Both groups of participants were told that the purpose of the study was to observe the sleep/wake schedule over a six-day period. Session two. When participants returned for the second session, the actigraph and the sleep diaries for Days 1 to 3 were collected and the Anxiety and Preoccupation about Sleep Questionnaire (APSQ) was administered. The Shown-Discrepancy Group then engaged in a behavioural experiment (the key experimental manipulation) that involved two parts. First, participants were shown and taught to read their actigraph recordings from the last 3 days, after the experimenter had downloaded their sleep data from the actigraph to a computer. Second, the participant completed a data summary sheet on which the sleep diary and the actigraph recordings were juxtaposed. The participants then calculated the discrepancy between the selfrated and objectively recorded sleep estimates. The aim of this exercise was to provide a clear and memorable demonstration of the discrepancy between how much participants thought they slept and how much the actigraph estimated they had actually slept. The procedure was identical for the No-Demonstration Group except that the participants in this group did not do the behavioural experiment. To index the impact of the behavioural experiment, participants were instructed to wear the actigraph for the next three nights and complete a sleep diary for the next three mornings (Days 4 to 6). Session three. During the final session, the actigraph and the sleep diaries for Days 4 to 6 were collected. All participants were asked to complete the APSQ with reference to the last three days. Results The analyses below involved a series of repeated measures ANOVAs with Group (Shown- 18

3 19 Discrepancy Group vs. No-Demonstration Group) as the between subjects factor and Session (Pre-experiment vs. Post-experiment) as the within subjects factor. To explore significant interactions, t-tests were conducted with a Bonferroni adjustment to control for multiple comparisons (p <.0125). The Effect of the Behavioural Experiment on Subjective Sleep Perception Subjective SOL estimates. Figure 1a depicts the change in subjective SOL for the two groups before and after the behavioural experiment. There was no significant main effect for Group. There was a significant main effect for Session, F(1, 38) = 13.78, p <.001, such that the SOL estimates were shorter after the behavioural experiment compared to before the behavioural experiment. There was a significant Group by Session interaction, F (1, 38) = 4.51, p <.05. Follow up tests indicated that the Shown-Discrepancy Group estimated their SOL to be shorter after the behavioural experiment relative to before the behavioural experiment, t (19) = 3.52, p <.002. This difference was not observed for the No-Demonstration Group. Subjective TST estimates. Figure 1b depicts the change in subjective TST for the two groups before and after the behavioural experiment. There was no significant main effect for Group. There was a significant main effect for Session, F(1, 38) = 14.47, p <.001, such that the TST estimate was longer after the behavioural experiment compared to before the behavioural experiment. There was no interaction. The Effect of the Behavioural Experiment on Sleep Related Anxiety The mean APSQ scores for the two groups before and after the behavioural experiment are depicted in Figure 2. There was no significant main effect for Group. There was a significant main effect for Session, F (1, 38) = 4.09, p <.05, such that the APSQ score was lower postexperiment relative to pre-experiment. There was also a significant Group by Session interaction, F (1,38) = 13.15, p <.001. Follow up tests indicated that the Shown-Discrepancy Group reported lower sleep-related anxiety and preoccupation after the behavioural experiment compared to before the behavioural experiment, t (19) = 3.83, p <.001. This difference was not observed for the No-Demonstration Group. Brief summary The first prediction tested was that the behavioural experiment would be associated with improved subjective sleep estimates. In support, the Shown-Discrepancy Group estimated their SOL to be shorter after, compared to before, the behavioural experiment. This difference was not significant for the No-Demonstration Group. The second prediction was that the behavioural experiment should be associated with reduced sleep-related anxiety and preoccupation. Consistent with this prediction, after the behavioural experiment, the Shown-Discrepancy Group reported significantly lower levels of anxiety and preoccupation about sleep compared to before the behavioural experiment, an improvement that was not observed for the No-Demonstration Group. These results are consistent with the proposal that distorted perception of sleep functions to maintain insomnia 19

4 Figure 1a. Subjective Sleep Onset Latency before and after the Behavioural Experiment 20 Subjective Sleep Onset Latency (minutes) ~~ Pre-experiment Shown-Discrepancy Group No-Demonstration Group Post-experiment Figure 1b. Subjective Total Sleep Time before and after the Behavioural Experiment. Subjective Total Sleep Time (hours) ~ Shown-Discrepancy Group No-Demonstration Group Pre-experiment Post-experiment 20

5 21 Figure 2. Total Score for the Anxiety and Preoccupation about Sleep Questionnaire (APSQ) before and after the Behavioural Experiment 60 APSQ Total Score Shown-Discrepancy Group No-Demonstration Group ~~ Pre-experiment Post-experiment Brief report on Experiment 2 Experiment 2 tested the proposal that distorted perception of sleep functions to maintain insomnia by manipulating perception of sleep immediately on waking and observing the effects on daytime functioning. Based on the cognitive model (Harvey, 2002), it was predicted that negative feedback would trigger more negative thoughts, increased monitoring for sleep-related threat, and increased safety behaviors relative to positive feedback. In addition, it was predicted that participants would report more sleepiness on negative feedback days relative to positive feedback days. Method Design The study employed a 2 (Feedback: negative, positive) by 3 (Day: 1, 2, 3) within-subjects design to experimentally manipulate subjective perception of sleep over three consecutive days. Immediately on waking, individuals with primary insomnia were presented with either negative feedback (last night s sleep was poor quality) or positive feedback (last night s sleep was good quality). Materials Actigraphy was included as the objective sleep estimate. An Electronic Display Unit (EDU) was used. The EDU is a small one-line text message pager unit (model: Ericsson Alpha 878i, supplied by British Telecom Inc.). As a disguise, the pager was refitted into a grey plastic box with a small window machined out so that only the liquid crystal display of the pager was visible. Procedure Session 1. The IDI and SCID were administered as a diagnostic check. Participants were fitted with the actigraph, which they were asked to wear for three consecutive nights. They were also given the EDU to place by their bedside. The participants were told that the actigraph would record their sleep quantity and sleep quality each night and that a summary of this information, translated into a sleep quality score, would be transmitted from the actigraph to the EDU each morning via a wireless communication system. Participants indicated their planned wake time for the three days and were informed that the transmission of feedback would be programmed through a central computer to occur automatically at that time each morning. Each participant 21

6 22 also received nine diaries, labelled as follows: Day 1 - On Waking Diary, Day 1 Midday Diary, Day 1 Evening Diary, Day 2 - On Waking Diary, Day 2 Midday Diary, Day 2 Evening Diary, Day 3 - On Waking Diary, Day 3 Midday Diary, and Day 3 Evening Diary in which they rated (1) negative thoughts, (2) monitoring, (3) safety behaviours and (4) sleepiness. While informed that the EDU feedback was generated by the actigraph recordings, in reality, participants were randomly assigned to receive a fully counterbalanced, pre-determined sequence of 2 negative and 1 positive feedback message or 2 positive and 1 negative feedback message (order of the three in each case was counterbalanced). The feedback sequences were assigned by consecutive order of recruitment (not by veridical sleep). The negative feedback was Sleep Quality = 1 and the positive feedback was Sleep Quality = 4 1. The following scale was printed on the face of the EDU to facilitate accurate interpretation of the feedback: 1 = poor sleep quality, 2 = fair sleep quality, 3 = moderate sleep quality, 4 = good sleep quality, 5 = excellent sleep quality. Session 2. The actigraph and daily diaries were collected. Participants were asked if they believed that the EDU had provided accurate feedback (response scale: yes, no). Six participants did not believe the feedback on one or more mornings and were therefore excluded. Results Objective Sleep Estimates To test if there were differences in objective sleep estimates based on feedback or night, two separate 2 (Feedback: negative, positive) 3 (Night: 1, 2, 3) repeated measures analyses of variance (ANOVA) were conducted, one for TWT and one for TST. No main effects or interactions reached significance. That is, in the analyses to follow, differences observed as a function of feedback cannot be attributed to the estimated differences in objective sleep obtained during the experiment. Daytime Measures Data from a total of 66 days were available for analysis (32 days following negative feedback, 34 days following positive feedback). All analyses were initially performed separately for the Midday Diary and the Evening Diary. As the results were identical, the midday and evening scores were averaged and overall mean scores reported. These will be referred to as the Daytime Negative Thoughts Score and the Daytime Sleepiness Score. To examine the effects of feedback on daytime processes, a series of 2 (Feedback: negative, positive) 3 (Day: 1, 2, 3) repeated measures ANOVAs was conducted for each of the dependent measures. There was a significant main effect for Feedback for all daytime variables. As depicted in Figure 3, negative feedback was associated with more negative thoughts, F (1, 21) = 18.42, p <.001, more monitoring, F (1, 21) = 11.00, p <.01, greater safety behaviors, F (1, 21) = 12.61, p <.001, and greater sleepiness, F (1, 21) = 9.15, p <.01, during the day relative to positive feedback. There were no significant effects for Day and no interactions. Brief summary Does distorting perception of sleep immediately on waking adversely affect daytime functioning? On days following negative feedback (that the sleep obtained was poor quality), participants reported more negative thoughts, greater sleepiness, more monitoring for sleeprelated threat, and greater use of safety behaviors relative to days when positive feedback (that the sleep obtained was good quality) was provided. These results are consistent with the proposal that impaired daytime functioning among insomnia patients is maintained, at least partly, by the subjective perception of inadequate sleep (Harvey, 2002). The results also support the proposed mechanism by which subjective perception is thought to operate; namely, by triggering a vicious cycle of cognitive processes that culminates in perceived daytime impairment (if sufficient sleep 1 A rating of 5 was not adopted as pilot testing indicated it was not believable. 22

7 23 was obtained on the previous night) or worsening of the daytime impairment (if insufficient sleep was obtained on the previous night) (Harvey, 2002). These results suggest that the impaired daytime functioning reported by insomnia patients (a core aspect of the disorder) is maintained, at least in part, by subjective perception of sleep. Figure 3. Mean daytime measures, collapsed across the three experimental days, for positive and negative false feedback conditions Negative Feedback Positive Feedback 5 4 *** ** ** *** Total Score Negative Thoughts Positive Affect Negative Affect Monitoring Safety Behaviours Sleepiness NNote. p =.06. **p <.01. ***p <.001. Brief report on Experiments 3 and 4 Experiments 3 and 4 were conducted to examine two of the proposed mechanisms by which patients with insomnia get tricked in to misperceiving their sleep: the role of excessive cognitive activity and the role of excessive physiological arousal. Before describing these studies two methodological points are worth comment. First, the procedure of both studies involved an afternoon nap session. The advantage of an afternoon nap session is that it (1) allowed tight experimental control over the procedure, (2) enabled testing to be conducted in a resource- and time-efficient manner, and (3) relevant only to Experiment 4, the testing format selected minimised potential ethical concerns about the impact of moderate to strong dose caffeine given at night on the sleep obtained on the following day. Further, it is noted that a number of studies in the insomnia literature have shown that an afternoon nap is a viable testing format [e.g., Wyatt et al., 1997]. Having said that, it will be important in future research to confirm that the findings of nap studies are a true analogue of nighttime sleep. Second, the participants for these study were good sleepers. This analogue sample was 23

8 24 selected because good sleepers are relatively free from distorted perception of sleep. Hence, it was possible to observe the effect of manipulating cognitive arousal on sleep perception with more clarity. Experiment 3 For Experiment 3 it was hypothesised that participants in the Anxious Cognitive Arousal Group and the Neutral Cognitive Arousal Group would (1) report worse sleep and (2) exhibit a greater discrepancy between self-reported sleep and actigraphy-defined sleep, relative to participants in the No Manipulation Group. The study was exploratory regarding the relative impact of anxious and neutral cognitive arousal on distorted perception of sleep. Design 24 Method Prior to the nap, participants were randomly allocated to one of three groups. The first group was the Anxious Cognitive Arousal Group who received a manipulation designed to raise the level of pre-sleep cognitive activity and anxiety ( speech threat ; n = 18). The second group was the Neutral Cognitive Arousal Group who received a manipulation designed to raise the level of pre-sleep cognitive activity without increasing anxiety ( essay task ; n = 18). The third group was the No Manipulation Group who received no manipulation and served as an index of baseline responding (n = 18). Five minutes after waking, the participants were asked to report their perception of the amount of sleep they had just obtained. Procedure Before the nap. The participants entered into a sound-attenuated sleep laboratory, where they were fitted with an actigraph (a sleep-monitoring device) before settling in bed. The participants were then instructed to lie in a supine position, with the lights-on and their eyes open, for a five-minute baseline period. When 5 minutes had elapsed, the participants were asked to rate their level of cognitive arousal [ In the last five minutes, how active or preoccupied by thoughts has your mind been? (Response scale: 1 Not at all preoccupied to 10 Very much preoccupied)] and anxiety [ In the last five minutes, how anxious have you felt? (Response scale: 1 Not at all anxious to 10 Very anxious)] with reference to their experience during the baseline period. Immediately prior to the nap, the experimental manipulation was administered. The Anxious Cognitive Arousal Group were given a speech threat. Participants in this group were told that they would be asked to give a speech to three psychologists and to a video camera on waking. The Neutral Cognitive Arousal Group were given an essay task. Participants in this group were told that they would be asked to write an essay on waking. The topic was identical for the speech task and the essay task ; both were asked to comment on foot and mouth disease in Britain (at the time of the study this was an impending national crisis). Two manipulation checks were administered immediately after they were told about their tasks; task difficulty and their task-induced anxiety. The No Manipulation Group were given no manipulation and were simply told to take a nap. Following that, participants were given one hour for the nap. As the crucial dependent variable was time perception, the participants were not informed of the duration of the nap (it was 1 hour long). After the nap. When the nap session was over, the participant was given 5 minutes to overcome sleep inertia and get back to the daytime mode (e.g., switching on the light, tightening loosened clothing, collecting their thoughts). A post-nap questionnaire was then administered, in which the participants estimated the time it took them to fall asleep (i.e., SOL) and the amount of time they had slept during the nap session (i.e., TST). In addition, the participants completed the Pre-sleep Cognitive Activity Questionnaire that indexed the presence of pre-sleep cognitive activity (Cronbach s alpha =.83; item-total correlation ranges from.58 to.87). This questionnaire was adapted from the cognitive subscale of the Pre-Sleep Arousal Scale by Nicassio and colleagues [PSAS] to measure neutral pre-sleep cognitive

9 25 activity. The total score of the PSAS will be referred to as the pre-sleep cognitive activity score. The participants were also asked to complete the STAI-state scale. This score will be referred to as the pre-sleep anxiety score. For both the STAI and the PSAS the initial instructions were slightly reworded so that the questions referred to the pre-nap period. Just before ending the session, the participants were probed as to whether or not they believed that they would be asked to give a speech or to write an essay (Response scale: Yes, No). Those who answered No to this question were considered to have failed the manipulation check (n = 4) and were thus not included in the final analysis. Baseline Variables Results There were no differences in the level of cognitive activity or anxiety following the fiveminute baseline period between the three groups. Manipulation Checks The Anxious Cognitive Arousal Group and the Neutral Cognitive Arousal Group did not differ in their rating of task difficulty. However, as expected, the Anxious Cognitive Arousal Group rated their task-induced anxiety higher compared to the Neutral Cognitive Arousal Group. Confirming our assumptions about the two manipulations, there was a significant difference for the pre-sleep cognitive activity score, such that both the Anxious Cognitive Arousal (p <.01) and the Neutral Cognitive Arousal (p <.01) Groups experienced more cognitive activity during the pre-sleep period compared to the No Manipulation Group. There was also a significant difference for the pre-sleep anxiety score, such that the Anxious Cognitive Arousal Group experienced more anxiety during the pre-sleep period compared to the Neutral Cognitive Arousal Group (p <.05) and the No Manipulation Group (p <.01). Discrepancy between Self-reported and Acitgraphy-defined Sleep Figure 4 depicts the amount of discrepancy between the self-reported and actigraphydefined SOL and TST. The discrepancy score was calculated by subtracting the actigraphydefined SOL and TST from the self-reported SOL and TST. A positive value denotes an overestimation, a negative value denotes an underestimation. There were significant differences in the discrepancy score for SOL [F (2, 51) = 8.47, p <.001] and the discrepancy score for TST [F (2, 51) = 5.10, p <.01]. The Anxious Cognitive Arousal Group (p <.01) and the Neutral Cognitive Arousal Group (p <.01) both overestimated the time it took them to get to sleep relative to the No Manipulation Group. Furthermore, the Anxious Cognitive Arousal Group underestimated the length of their nap compared to the No Manipulation Group (p <.05). 25

10 26 Figure 4. Discrepancy Scores by Group 40 Anxious Cognitive Arousal Group Neutral Cognitive Arousal Group No Manipulation Group Discrepancy (minutes) ** ** -40 Sleep Onset Latency Discrepancy 26 * Total Sleep Time Discrepancy Note. Discrepancy = Subjective SOL/TST Objective SOL/TST. A positive score denotes overestimation. A negative score denotes underestimation. Vertical lines depict standard errors of the means Asterisks represent significant differences relative to the No Manipulation Group. * p <.05, ** p <.01. Experiment 4 Experiment 4 adapted the methods established in Experiment 3 to investigate the relative impact of anxious cognitive arousal versus physiological arousal on sleep perception. Several hypotheses were tested. First, it was predicted that the Anxious Cognitive Arousal Group would report worse sleep and exhibit more distorted perception of sleep compared to controls, replicating the findings of Experiment 3. As no previous research has directly compared the two competing proposals of mechanisms that underpin distorted perception of sleep, the study was exploratory with regard to the relative impact of anxious cognitive arousal and physiological arousal on sleep perception. Design Method Prior to the nap, participants were randomly allocated to one of three groups. The first group was the Anxious Cognitive Arousal Group who received a manipulation that was designed to raise the level of pre-sleep cognitive activity and anxiety ( speech threat ; n = 18). The second group was the Physiological Arousal Group who swallowed a caffeine capsule that was intended to raise the level of pre-sleep physiological arousal without also increasing cognitive activity (n = 18). The third group was the Placebo Group who swallowed a placebo capsule and served as a

11 27 control for possible placebo effect due to the capsule administration (n = 18). Five minutes after waking, the participants were asked to report their perception of the amount and the quality of sleep they had just obtained. Procedure Before the nap. The participants were introduced to the sleep laboratory for a 5-minute baseline period. Then the participants were asked to complete the Pre-sleep Cognitive Activity Questionnaire (described in Experiment 1), the STAI- state scale and a Pre-sleep Physiological Arousal Questionnaire [comprised 5 questions to measure caffeine-related physiological arousal; Cronbach s alpha =.71, item-total correlations ranges from.36 to.81] with reference to their experience during the baseline period. The participants were then asked to engage in 20 minutes of leisure-reading. This involved browsing a selection of neutral but engaging travel guides. Previous pharmacological research has indicated that the effect of caffeine is not immediate, taking typically around 30 minutes to take effect after ingestion. That is, with the 20 minutes of leisure-reading and several minutes for further instructions and ratings, the effect of the caffeine should have been kicking in at the beginning of the nap. In a double-blind fashion, participants in the Physiological Arousal Group and the Placebo Group were given either a caffeine capsule or a placebo capsule to swallow approximately 25 minutes prior to the beginning of the nap. The dosage of the capsule varied from 250 mg to 450 mg depending on the body weight of the participants (5 mg/kg). To check if the participants were truly blind to the allocation of the capsules, they were asked to rate their guess as to the content of the capsule on a 7-point scale (Response scale: 1 Certainly not a caffeine capsule to 4 Don t know to 7 Certainly a caffeine capsule). When the leisure reading task was over, participants in the Cognitive Arousal Group were given the speech threat. The topic of the speech was to present a talk based on what they had read from the tour guides. The participants were then asked to rate, on a 10-point scale, how anxious they felt about having to give a speech (Response scale: 1 Not at all anxious to 10 Very anxious). All participants were then given an hour for the nap. As for Experiment 1, they were not informed as to the duration of the nap session. After the nap. Five minutes after waking, a post-nap questionnaire was administered, in which the participants estimated their SOL and TST. The participants then re-completed the baseline measures. Just before ending the session, the participants were probed as to whether or not they believed that they would need to give a speech (Response scale: Yes, No). Those who answered No to this question were considered to have failed the manipulation check (Anxious Cognitive Arousal Group: n = 8) and were thus not included in the final analysis. Baseline Variables 27 Results There were no differences in the level cognitive activity, anxiety or physiological arousal following the 5-minute baseline period across the three groups. Manipulation Checks The participants in the Anxious Cognitive Arousal Group felt anxious when they received the speech threat. Confirming our assumptions about the speech threat, there was a significant difference for pre-sleep cognitive activity score, such that the Anxious Cognitive Arousal Group experienced more cognitive activity during the pre-sleep period, compared to the Physiological Arousal Group (p <.01) and the Placebo Group (p <.001). There was also a significant difference for pre-sleep anxiety score, such that the Anxious Cognitive Arousal Group experienced more anxiety during the pre-sleep period, compared to the Placebo Group (p <.001). The participants in the two capsule-taking groups were equally blind to the allocation of the capsules. Confirming our expectation of the administration of the caffeine and placebo capsules,

12 28 there was a significant difference for pre-sleep physiological arousal score, such that the participants in the Physiological Arousal Group experienced more bodily arousal compared to the Placebo Group (p <.05). Discrepancy between Self-reported and Actigraphy-defined Sleep Figure 5 depicts the amount of discrepancy between the self-reported and actigraphydefined SOL and TST. The calculation of the discrepancy score was identical to Experiment 1 in that a positive value denotes an overestimation, a negative value denotes an underestimation. There were significant differences in the discrepancy scores for SOL [F (2, 51) = 4.07, p <.05] and for TST [F (2, 51) = 10.2, p <.001]. The Anxious Cognitive Arousal Group significantly overestimated the time it took them to get to sleep relative to the Placebo Group (p <.05). There was also a trend (p <.052) such that the Physiological Arousal Group also overestimated the time it took them to get to sleep compared to the Placebo Group. Relative to the Placebo Group, both the Anxious Cognitive Arousal Group (p <.001) and the Physiological Arousal Group (p <.01) significantly underestimated the length of the sleep they obtained from the nap. Brief summary of Experiments 3 and 4 These two interlinked experiments investigated the association between distorted perception of sleep and two types of pre-sleep arousal; cognitive arousal and physiological arousal. The evidence indicates that both pre-sleep cognitive arousal and pre-sleep physiological arousal appear to contribute to distorted perception of sleep. Figure 5. Discrepancy Scores by Group Anxious Cognitive Arousal Group Physiological Arousal Group Placebo Group Discrepancy (minutes) * Sleep Onset Latency Discrepancy *** ** Total Sleep Time Discrepancy Note. Discrepancy = Subjective SOL/TST Objective SOL/TST. A positive score denotes overestimation. A negative score denotes underestimation. Vertical lines depict standard errors of the means. Asterisks represent significant differences relative to the Placebo Group. * p <.05, ** p <.01, *** p <

13 Activities/Outputs This research is in the process of being written up for publication. It is expected that three scientific papers will be submitted for publication in peer reviewed journals (Studies 3 and 4 will be combined into one paper). In addition, the results of Experiment 1 have been submitted for presentation at the European Association for Cognitive and Behaviour Therapy (EACBT) to be held in Manchester next year and the results of Studies 3 and 4 will be submitted for presentation at the American Society for Sleep Medicine (ASSM) conference to be held in Philadelphia next year. Impacts of research 1. Has contributed to the validation and further development of a new theory of insomnia. 2. Has provided support for two competing theories, the cognitive account and the arousal account, as to the mechanism that underpins distorted perception of sleep. 3. Has established methods for delineating mechanisms that fuel distorted perception. 4. Has provided a new body of knowledge on (i) the role of distorted perception of sleep in insomnia and (ii) the mechanisms underpinning distorted perception of sleep. 5. Has contributed to the body of knowledge that can be used to derive a new, highly effective treatment for insomnia. For example, a novel procedure was developed that has potential to become a helpful intervention for insomnia patients (Experiment 1). Future research priorities 1. Several novel paradigms have been established that, in future studies, should be extended by using polysomnography as the measure of sleep, rather than actigraphy. Polysomnography is currently the gold standard for the objective assessment of sleep. 2. Further to point 1, and as a followup to Experiments 3 and 4, future research should adopt polysomnography as a measure to enable analysis of the EEG for subtle abnormalities in sleep including increased Beta EEG during sleep onset. It is possible that abnormalities in the perception of the sleep state or very brief awakenings contribute to distorted perception (Perlis et al., 2001). 3. Future research on distorted perception of sleep should also aim to further develop the literature showing that patients with insomnia tend to interpret sleep as wakefulness. For example, Mercer et al. (2002) found that when insomnia patients were woken up 5 minutes after the onset of Stage 2 sleep or during uninterrupted rapid eyes movement (REM) sleep, individuals with insomnia were more likely than the good sleepers to report experiencing wakefulness the moment just prior to being woken up. Further, Mercer et al. (2002) found that this tendency to interpret sleep as wakefulness correlated significantly with distorted perception of sleep. 4. Experiment 1: as participants were followed up for 3 days future research is required to test the long term durability of the behavioural experiment. 5. Experiment 2: a future study is required to include a no feedback control condition so that we can determine whether the effects observed are due to the negative feedback, the positive feedback or both. 6. Testing other predictions of the new theoretical model (Harvey, 2002). 7. Using the results from experiments testing predictions of the model to develop new, more effective interventions for insomnia

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