REM dream activity of insomnia sufferers: a systematic comparison with good sleepers

Accepted Manuscript Title: REM dream activity of insomnia sufferers: a systematic comparison with good sleepers Author: Alexandra D. Pérusse, Joseph De Koninck, Maude Pedneault-Drolet, Jason G. Ellis, Célyne H. Bastien PII: DOI: Reference:

S1389-9457(15)00905-3 http://dx.doi.org/doi: 10.1016/j.sleep.2015.08.007 SLEEP 2864

To appear in:

Sleep Medicine

Received date: Revised date: Accepted date:

24-3-2015 5-8-2015 10-8-2015

Please cite this article as: Alexandra D. Pérusse, Joseph De Koninck, Maude Pedneault-Drolet, Jason G. Ellis, Célyne H. Bastien, REM dream activity of insomnia sufferers: a systematic comparison with good sleepers, Sleep Medicine (2015), http://dx.doi.org/doi: 10.1016/j.sleep.2015.08.007. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Running head: REM DREAMS AND INSOMNIA

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REM dream activity of insomnia sufferers: A systematic comparison with good sleepers

Alexandra D. Pérusse, BA1-2, Joseph De Koninck, PhD3, Maude Pedneault-Drolet, BA1-2, Jason G. Ellis, PhD4, & Célyne H. Bastien, PhD1-2

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École de psychologie, Université Laval, Québec, Qc, Canada; 2Laboratoire de sommeil et potentiels évoqués cognitifs du Centre de recherche de l’Institut universitaire en santé mentale de Québec, Québec, Qc, Canada; 3 School of Psychology, University of Ottawa, Ottawa, ON, Canada; 4 Northumbria Centre for Sleep Research, Northumbria University, Newcastle, UK.

The present study was conducted at Laboratoire de sommeil et potentiels évoqués cognitifs du Centre de recherche de l’Institut universitaire en santé mentale de Québec, Québec, Qc, Canada.

This study was supported by the Canadian Institutes of Health Research (CIHR; # 49500, 86571)

Conflict of interest statement: The authors have no potential conflict of interest to declare.

Corresponding author: Célyne H. Bastien Pavillon Félix-Antoine-Savard 2325 rue des Bibliothèques Office 1012 Université Laval Québec, Qc, Canada, G1V 0A6 Phone number: +1-418-656-2131, ext. 8344 Fax number: +1-418-656-3646 Email address: [email protected]

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Highlights – REM dream activity of insomnia sufferers: A systematic comparison with good sleepers

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Dream activity in insomnia sufferers is characterized by greater negative content. Less positive emotion was found in dreams of insomnia sufferers. Insomnia sufferers subjectively evaluate their dreams more negatively. High negative dream content is associated with low sleep efficiency in insomniacs. Dream activity in insomniacs seems in line with their negative waking experiences.

Abstract Objective: Dream activity of patients with primary insomnia (PI) has rarely been studied, especially using in-lab dream collection, even though dreams could be linked to their state of hyperarousal and their negative waking experiences. The objective was to compare patients with PI and good sleepers controls (GSC) on dream recall frequency and dream content. Patients/Methods: Polysomnography was recorded on 12 PI sufferers and 12 GSC (aged between 30 and 45) for five consecutive nights. Enforced REM sleep awakenings occurred on nights 3 and 5 for dream collections. Results: REM dream collections revealed the groups were similar on dream recall frequency (p≤.7). On dream content variables, GSC's dreams tended to comprise more positive emotions (p=.06) whereas the dreams of patients with PI were characterized by more negative elements than positive ones (p=.001). Subjectively, GSC characterized their dreams as being more pleasant and containing more joy, happiness and vividness (p≤.03) than patients with PI. Finally, elevated negative dream content was associated with lower sleep efficiencies in insomnia (p=.004). Conclusion: These results suggest that less positive emotions and greater negative content characterize the dreams of patients with PI and seem to be in line with their waking experiences.

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One potential explanation could be hyperarousal exacerbating pre-sleep negative mentation and thus contributing to poorer sleep quality. The lack of difference in dream recall frequency is most likely due to the forced awakening ‘dream collection’ procedure. The study of dream activity seems a promising avenue to better understand the 24-hour experience of insomnia and explore the potential benefits of dream management techniques. Keywords: Insomnia, dream activity, hyperarousal, continuity hypothesis, REM sleep, in-lab dream collection, dream content, dream recall frequency. Introduction Insomnia is the most prevalent of sleep disorders, being diagnosed in more than 13% of the general population (Morin et al., 2011) with 1 to 2% suffering from primary insomnia (PI; Ohayon, 2002). In addition, another 30 to 48% reports insomnia symptoms, without meeting full diagnostic criteria (Ohayon, 2002). This disorder is largely characterized by reports of nocturnal disruptions (difficulties initiating and/or maintaining sleep; AASM, 2014; APA, 2013) and their impact on diurnal functioning (Morin et al., 2011). One interesting, but poorly studied question is how insomnia manifests during the night through dream activity - defined as mental activity occurring during sleep (De Koninck, 2012; Schredl & Wittmann, 2005). The most prominent model in dream research, the continuity hypothesis (Hall & Nordby, 1972), states that the dream is largely a reflection of the individuals’ waking experiences (for a review, see Domhoff, 2003; 2010). As such, this model could suggest that the negative pre-sleep cognitive arousal (for a review, see Hantsoo et al., 2013) experienced by patients with PI could translate into their dream activity, resulting in more negatively toned dreams. Moreover, knowing that patients suffering from PI generally display more neuroticism, and dysfunctional beliefs about sleep and that insomnia is characterized by negative daily

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consequences and concerns such as physical/psychological health problems, fatigue, mood disturbances and cognitive alterations (Beaulieu-Bonneau, LeBlanc, Vérette, Dauvilliers, & Morin, 2007; Morin et al., 2011; Van de Laar et al., 2010), it would be reasonable to assume that the dreams of PIs would be negatively affected and they would report more nightmares than normal subjects. Certainly post-traumatic stress disorder, of which nightmares are a significant feature, has been associated with increased physiological and cognitive arousal (e.g. Germain & Nielsen, 2003). While there have been relatively few studies examining these assumptions, the data that does exist suggests that PIs report a higher prevalence of nightmares compared to good sleepers controls (GSC; Ohayon et al., 1997; Pagel & Shocknesse, 2007; Schredl, 2009a, b) and that nightmare frequency is related to the severity of insomnia symptoms. Schredl (2009a) suggests that this increased presence of nightmares in insomnia further exacerbates symptom reporting due to the nightmare interrupting the sleep process itself (increased awakenings) but also due to the fear of having a nightmare, which could contribute to sleep onset difficulties. As for reported dream content, while one study found more negative elements in the sleep onset dreams of patients with PI, which the authors attributed to heightened cognitive arousal (Antrobus & Saul, 1980), another did not find any difference in dream content between patients with PI and GSC (Freedman & Sattler, 1982). Thus far, only one group has used in-lab REM sleep awakenings in patients with PI to study dream content. They found that PIs tend to characterize themselves negatively in their dreams (e.g. low self-esteem, lack of something; Ermann, 1995). Schredl and colleagues (1998) obtained similar findings using questionnaires and in-lab morning collected dream reports. In their study, negativity of the dream content was coded using the negative emotions scales (Hall & Van de Castle, 1966) and dichotomous scales

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(Yes/No) for aggression and physical interactions as well as a scale to evaluate the occurrence of minor problems (e.g. arguing) and major ones (e.g. being chased). Overall, Schredl et al. (1998) observed that dreams of PIs tended to comprise: i) more negative elements, ii) more negative emotions and, iii) more overall problems compared to GSC. Central to our understanding of increased nightmare frequency and negative dream content in primary insomnia is the concept of heightened arousal - proposed by the neurocognitive model of insomnia (Perlis et al., 1997). According to this model, in order to palliate for their sleep difficulties, patients with PI tend to develop maladaptive behaviors, contributing to increased somatic, cognitive and cortical activation (Morin, 1993). These activations then exacerbate evening worries and ruminations, delaying sleep onset. Perhaps more importantly, the neurocognitive model of insomnia also states that as levels of activation during sleep are closer to waking thresholds in PIs – heightened arousal has been well documented in studies of both the sleep microstructure and macrostructure of PIs (for a review, see Bastien, 2011) – dreams are more likely to be encoded as short-term memories and transferred to longterm memory during sleep. As such, the neurocognitive model of insomnia (Perlis et al., 1997) would postulate that dream recall overall (irrespective of dream content or the presence or absence of nightmares) should be higher in PIs compared to GSCs due to this ‘hyperarousal state’. However, the relatively few studies of dream recall frequency in insomnia have produced quite contradictory results. Indeed, some groups found a lower dream recall frequency in patients with PI compared to GSC, using questionnaires (Pagel & Shocknesse, 2007; Schredl et al., 1991) and in-lab dream collection (Ermann et al., 1993), whereas others have observed a higher dream recall frequency in PIs compared to GSCs using questionnaires (Schredl et al., 1998) and some have found no group differences (Schredl et al., 1991). Although the findings on dream recall are

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inconsistent, strong relationships have nonetheless been observed between the frequency of nocturnal awakenings and the frequency of dream recall in GSC (Cory & Ormiston, 1975; Schredl, Wittman, Ciric, & Götz, 2003) and patients with PI (Li, Zhang, Li, & Wing, 2010; Ohayon, Morselli, & Guilleminault, 1997). As nocturnal awakenings enhance the transfer of dream content from short term to long-term memory, facilitating memory consolidation, therefore making dream recall easier in the morning (Koulack & Goodenough, 1976), it may well be that an awakening is necessary for consolidation but that PIs may be more susceptible to awakenings due to hyperarousal. The need for an actual awakening would also explain the increases in dream recall frequency when in-lab awakenings for dream collection are used compared to diaries and questionnaires (Domhoff, 2003). In summary, previous results on dreams in PI have been variable depending upon the dimensions examined (nightmare frequency, dream recall, dream content) and the method of data collection (in-lab REM awakenings versus morning recall). Moreover these studies have mostly been based on diaries and questionnaires with only one study using a valid scale to describe dream content (i.e. the Hall & Van de Castle scale, 1966). As such a study was required to characterize the dreams of patients with PI, compared to GSCs, with these considerations in mind. Objectives and hypotheses The aim of the study was to compare patients with PI and GSC on the various dimensions of dream activity. Specifically, in response to forced REM awakenings and in accordance with the continuity theory and the neurocognitive model of insomnia, it was hypothesized that:

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1) The dreams of patients with PI would be characterized by more negative than positive content compared to GSCs. Using the Hall & Van de Castle system (1966), this would be translated through more reports of aggressions, misfortunes, failures and negative emotions. 2) Patients with PI would subjectively evaluate their dreams as containing more negative emotions and as being more unpleasant than GSCs. 3) Sleep efficiency would be negatively associated with negative dream content and this would be more pronounced in PIs. 4) Dream recall frequency would be similar between groups since participants were systematically awakened from REM sleep. Still, recollections of patients with PI would be more intense and of better quality. On a questionnaire measuring general dream and nightmare recall frequency, it was predicted that patients with PI would report recalling more dreams and nightmares than GSCs, considering they experience more nocturnal awakenings. Method Participants Two groups of participants were recruited for this study: 12 patients with PI and 12 GSC. All participants were aged between 30 and 45. The inclusion criteria for insomnia were: a) a subjective complaint of insomnia characterized by difficulties initiating and/or maintaining sleep; b) complaints of sleep difficulties for at least three nights a week for six months or longer; c) a complaint of at least one daytime consequence attributed to the insomnia; d) distress or significant difficulties in social and/or occupational functioning and; e) a subjective sleep efficiency (SE) below 85%. GSCs had to report: a) sleeping a minimum of seven hours per night;

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b) being satisfied with their sleep and having no sleep complaints; and c) a subjective SE exceeding 85%. Exclusion criteria for both groups were: a) a significant medical disorder; b) a major psychopathology; c) other sleep disorders; d) a strong dependency to tobacco triggering nocturnal awakenings for smoking; e) an ongoing psychological treatment; f) use of a medication known to affect sleep; g) a score > 23 on the Beck Depression Inventory (BDI; Beck et al., 1996); or h) a score > 15 on the Beck Anxiety Inventory (BAI; Beck & Steer, 1993). Inclusion and exclusion criteria were consistent with those of the International Classification of Sleep Disorders 2 for chronic psychophysiological insomnia and chronic sleep misperception (ICSD-2; AASM, 2005). However, PSG confirms that most of the PI participants suffered from chronic psychophysiological insomnia. Procedure Participants were recruited through emails sent to the Laval’s University community. Following a brief screening phone interview, eligible participants were sent a series of questionnaires to evaluate psychological symptoms [BAI (Beck & Steer, 1993) and BDI (Beck et al., 1996)], sleep difficulties [Insomnia severity index (ISI; Morin, 1993) and two weeks of sleep diaries (Morin, 1993)] and dream activity (One dream diary and a questionnaire on general dream/nightmare recall frequencies). Those who met inclusion criteria for any of the two groups were invited to the sleep laboratory for clinical interviews. Upon arrival, informed consent was obtained. The Mini International Neuropsychiatric Interview (M.I.N.I.; Sheehan et al., 1998) was administered to rule out major psychopathologies, the Insomnia Diagnosis Interview (IDI; Morin, 1993) to explore the nature of insomnia symptoms and the Rivermead Behavioural

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Memory Test, 3rd Edition (RBMT-3; Wilson, Cockburn, Baddeley, & Hiorns, 1989) to assess memory functioning. These evaluations were conducted by a graduate student in a clinical psychology / neuropsychology program (ADP). Participants meeting study criteria underwent five consecutive nights of PSG recordings during which their typical bedtime schedules were respected and a minimum of 8 hours in bed were recorded. The first night was used for screening and adaptation purposes. Clinical data of objective and subjective sleep parameters were obtained on nights 2 and 4 (recorded at home with ambulatory devices) and nights 3 and 5, (in lab). In-lab REM sleep dream collections were used during nights 3 and 5 using a well-validated procedure at the University of Ottawa (e.g. Grenier et al., 2005) described hereafter. In-lab dream collection procedure. REM sleep awakenings were triggered using an 80 decibels tone so participants were abruptly awoken, which has been shown to limit intrusions and facilitate recall (Goodenough, Lewis, Shapiro, Jaret, & Sleser, 1965). This awakening method has been used for many years and is still successfully used in recent studies (e.g. Grenier et al., 2005). Awakenings were generated during each REM sleep period, except during the first one since it is usually too short and difficult to interrupt. An awakening was induced 10 minutes after the beginning of the second REM sleep period, 15 minutes in the third one and 20 minutes following the beginning of subsequent REM sleep periods. In order to limit awakening time, thus minimizing the perturbation of their sleep, participants were instructed to narrate over the intercom their dreams as soon as they were awoken by the tone. The use of an intercom prevented visual contact between participant and the interviewer during dream narration reducing potential transference and censorship. Once spontaneous reporting was completed, participants were briefly questioned over the intercom to encourage them to report all the dream elements they could remember. Interactions were kept to a minimum to limit collection bias

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variables. Finally, participants verbally answered a brief mood checklist about their dream, and were then invited to go back to sleep. There was no in-room intrusion during the whole procedure. Dream reports were also recorded on audio bands and later transcribed on the computer to facilitate coding using the Hall & Van de Castle system (1966). This procedure was approved by the ethics comity of the Centre de recherche de l’Institut universitaire en santé mentale de Québec (CER; # 306-2012). Measures To evaluate psychological symptoms, the BAI (Beck & Steer, 1993), BDI (Beck et al., 1996) and the M.I.N.I. (Sheehan et al., 1998) were administered. Prior to PSG recording nights, dream activity was evaluated using a dream diary and a questionnaire on dream/nightmare recall frequency. To explore sleep difficulties, the ISI (Morin, 1993) was completed as well as a twoweek sleep diary that assessed subjective sleep quality, requiring participants to report their sleep habits, such as the number of awakenings, the length of each awakening and the time spent in bed (Morin, 1993). Adequate psychometric properties have been reported for both measures in previous studies (Bastien, Vallières & Morin, 2001; Morin et al., 2011). Also, the IDI (Morin, 1993) was used to evaluate the presence of insomnia and its contributing factors. The RBMT-3 (Wilson, Cockburn, Baddeley, & Hiorns, 1989) was administered to ensure that results on dream activity were not better explained by memory functioning since it is known to be significantly altered in insomnia (for a recent meta-analysis, see Fortier-Brochu, Beaulieu-Bonneau, Ivers, & Morin, 2012). After each REM sleep awakening, participants answered verbally a brief mood checklist which was elaborated upon using the emotions from the Hall & Van de Castle scales (1966),

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with the addition of joy, fear and anxiety. Compared to happiness, which was conceptualized has being more trait related, joy was considered to be more state related and the same was conceptualized for fear (state related) while apprehension is also more trait related. Anxiety was added since it is a concept well understood by participants. Therefore, the mood checklist subjectively evaluated the emotional content of the dream (joy, happiness, apprehension, anger, sadness, confusion, fear and anxiety), its vivacity, its nature (pleasant/unpleasant) and the quality of recall (amount of details included in dream recall). These elements were subjectively evaluated by participants using a 4-point Likert scale (1 – ‘not at all’ to 4 – ‘a lot’). Dream recall frequency was calculated for nights 3 and 5 separately by dividing the number of times a dream was recalled by the frequency participants were awoken during REM sleep. Also, prior to laboratory nights, participants were asked to report their habitual dream and nightmare recall frequencies using two distinct questions on a 6-point Likert scale (1 – Less than once a month; 2 – Approximately once a month; 3 – Approximately once every 2 weeks; 4 – Approximately once a week; 5 – Several times a week; and 6 – Almost every night). PSG recordings. PSG was recorded over five consecutive nights. The same standard PSG montage was used for laboratory and ambulatory nights, including electroencephalography (EEG; F3, F4, C3, C4, O1 and O2), electromyography (EMG; electrodes on chin), electrocardiography (ECG; electrode on heart) and electro-oculography (EOG; one electrode on the supra-orbital ridge of the right eye and another on the infra-orbital ridge of the left eye) recordings. Reference electrodes were fixed on the mastoids and the ground was located at Cz. On the first night (adaptation night), leg EMG (electrodes on the tibialis) and breathing devices (nasal flux to measure oxygen saturation and thoracic bands) were used in order to detect, respectively, limb movements and breathing disorders. During nights 2 and 4, a Stellate Notta

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(1998) ambulatory device was used. During laboratory nights (1, 3 and 5), signals from the electrodes were amplified with a Grass Model 15A54 amplifier system (Astro-Med Inc., West Wrawick, USA; gain 10000; bandpass 0.3-100 Hz). Throughout the five recording nights, the inter-electrode impedance was maintained below 5kΩ and PSG signals were digitized at a sampling rate of 512 Hz with the commercial product Harmonie (Stellate system, Montreal, Canada). PSG recordings were visually scored (Luna, Stellate system, Montreal, Canada) by an experimented sleep technician using Rechtschaffen and Kales’ criteria (1968) at 20-second epochs. Hall & Van de Castle coding system. The Hall & Van de Castle coding system (1966) was used to analyse dream content. This system allows the attribution of frequencies to different elements in the dream by associating them to standard categories of content. For this study, negative oneiric content was derived from the sum of negative elements: aggressions, misfortunes, failures and negative emotions from the Hall & Van de Castle scale (1966), and positive content was measured by adding together friendliness, good fortunes, successes and positive emotions. Otherwise, every positive and negative variable was computed individually, as well as characters for intergroup comparisons. To maximize coding validity, dreams were analyzed by two independent evaluators, blind to participants’ group status. Each variable coded was then discussed until an agreement was reached. Length of dreams had to be between 40 and 350 words in order to be coded, but every dream activity recalled, independently of its length, was included in dream recall frequency calculations. Statistical analyses

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Independent sample t-tests were computed to compare groups on socio-demographic data, psychological characteristics and memory functioning. Gender and general dream/nightmare recall frequency were both evaluated with non-parametric tests for independent samples (Chi-square and Mann-Whitney U respectively). Repeated measures ANOVAs were performed to compare GSC and patients with PI on objective and subjective sleep parameters on the four experimental nights. For oneiric content, each variable of interest was added and divided by the number of dreams, thus creating means per dream for every participant. Paired sample ttests were then performed to determine if there were significant differences in mean negative and positive elements between PIs and GSCs. The groups were also compared on individual dream content variables using independent sample t-tests. In order to identify main effects of group on subjective mood checklist items, a non-parametric test for independent samples (Mann-Whitney U) was conducted. Pearson’s correlations were computed to identify relationships between objective sleep quality and negative dream content as a whole. Analyses were performed on nights 3 and 5 independently. Finally, a repeated measures ANOVA was performed to compare both groups on dream recall frequency. A significance level (alpha 0.05) was set for all analyses. Results Socio-demographic, psychological and memory functioning variables Table 1 shows no significant between group differences for gender (p = 1.0), age (p = .9) and education (p = .8), which varied from 11 to 21 years. Patients with PI reported mean insomnia duration of 21.1 years (SD = 15.9), ranging from 1.3 to 44.0 years. The severity of insomnia symptoms, as measured by the ISI, varied between 0 and 12 and was significantly greater in patients with PI compared to GSC (p ˂ .001). No significant difference was found

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between both groups for depressive symptoms (BDI; p = .9), scores ranging from 0 to 22, and anxiety symptoms (BAI; p = .8), scores ranging from 0 to 14. Memory functioning, as evaluated by the global memory index of the RBMT-3, was similar for both groups of sleepers (p = .9), ranging from 71 to 121. Scores obtained on the story immediate recall and story delayed recall subtests of the RBMT-3, which are the most closely related to dream recall, were not significantly different between the groups (p ≥ .5). There was no main effect of group for subjective dream recall (p = .7) or nightmare recall frequencies (p = 1.0). See Table 1 for more details on socio-demographic, psychological and memory functioning variables. ---------------------------------------------- Insert Table 1 here ----------------------------------------------Objective and subjective sleep parameters For ambulatory nights (2 and 4) as illustrated in Table 2, an examination of objective sleep parameters revealed significant between group differences for wake after sleep onset (WASO) and SE (p = .03), where patients with PI spent more time awake after sleep onset and had a lower SE than GSC. There was no main effect of group for objective sleep onset latency (SOL; p = .8), total wake time (TWT; p = .06) and total sleep time (TST; p = .2). However, Table 3 shows that when sleep was disturbed with dream collections during nights 3 and 5, both groups were similar on all objective sleep parameters (.1 ≥ p ≤ .7). For subjective sleep parameters of nights 2 and 4, as illustrated in Table 2, there were no between group differences on SOL (p = .10), but Table 3 shows that groups were significantly different during nights 3 and 5 (p = .05); patients with PIs reporting a longer time to fall asleep than GSCs. On all 4 nights, subjective WASO and TWT were significantly greater in patients with PI compared to GSCs (p ≤ .02). PIs reported a shorter TST (p ≤ .03) and their SE was

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significantly poorer than GSCs (p ≤ .001). Tables 2 and 3 illustrate means and SDs for each of the above variables. ---------------------------------------------- Insert Tables 2 & 3 here ---------------------------------------REM sleep dream activity There were no between group differences on dream length (p = .14). Table 4 illustrates the results from paired sample t-tests between mean negative and mean positive dream content showing that independent of grouping, the amount of negative elements was significantly higher than positive ones. Interestingly, when groups were examined separately, this significant difference remained only for patients with PI (p = .001) with a very large effect size (d =1.31). In other words, the dreams in PIs are characterized by significantly more negative than positive elements. As expected, controlling for dream length did not affect this finding. However, Table 5 shows that when the groups were compared on negative and positive elements with independent sample t-tests, no significant differences were found (p≤ .17). Similarly, intergroup comparisons for each individual variable revealed no significant differences (.12 ≤ p ≤ .90), except for positive emotions, which tended to be higher in dreams of GSCs (p = .06; See Tables 4 & 5 for more details). ------------------------------------------- Insert Tables 4 & 5here -------------------------------------------Table 6 illustrates the results from analyses conducted on subjective evaluations of dream content using each item from the mood checklist. Significant between group differences were observed for joy (p = .006) and happiness (p = .033); these two emotions being reported more frequently in dreams of GSCs than patients with PIs. Also, GSCs subjectively reported a higher degree of vividness (p = .003) in their dreams, which were characterized as being more pleasant

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(p = .014) than patients with PI. No significant between group difference was observed for the other subjective variables (anxiety, fear, apprehension, anger, sadness, confusion, recall quality and unpleasant content; .21 ≤ p ≤ .82; See Table 6 for means and SD). ------------------------------------------------ Insert Table 6 here --------------------------------------------A repeated measures ANOVA revealed that in-lab dream recall frequency was similar in both groups (p = .2). Descriptively, patients with PI tended to recall their dreams more often than GSC when awoken from REM sleep [(Night 3: 95.8% vs. 91.0 %) and (Night 5: 95.8% vs. 89.6%)] respectively. Relationships between sleep quality and negative dream content When groups were combined, negative dream content and objective SE were significantly correlated only for night 5 (R = -.53, p = .007), tentatively suggesting that negative dream content may be associated with worse sleep quality. Interestingly, when the groups were separated this significant relationship remained only for patients with PI. On night 5, increased SE was associated with less recall of negative elements in dreams (R = -.76, p = .004). Discussion As expected, analyses revealed that both groups of sleepers were equivalent on sociodemographic variables, psychological measures and memory functioning, thus limiting confounding variables and facilitating group comparisons. Insomnia duration was over 20 years, suggesting that disturbed sleep patterns of patients with PI were well established and representative of chronic primary insomnia. The usual sleep pattern of patients with PI (i.e. prolonged nocturnal awakenings and poor sleep efficiency) was evidenced by longer objective

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WASO and poorer objective SE in the PI group compared to GSC group during the undisturbed nights (2 & 4). The lack of group differences for objective SOL probably resulted from the type of nocturnal difficulties experienced by patients with PI in our study, who seemed to suffer from middle and/or terminal insomnia rather than initial insomnia. Subjectively, patients with PI reported significantly longer SOL, WASO and TWT, shorter TST and poorer SE compared to GSC, illustrating the tendency to underestimate sleep quality and quantity in insomnia. The main objective of this study was to compare patients with PI and GSC on several dimensions of their dreams obtained by forced REM sleep awakenings. It was hypothesized that the dreams of patients with PI would reflect their higher level of arousal and their pre-sleep negative experience through more negative than positive elements. As expected, a significantly higher amount of negative elements was observed in dreams of patients with PI. While this observation is consistent with both the continuity hypothesis and the hyperarousal model of insomnia, the lack of measures of arousal in our protocol favors the more parsimonious explanation of continuity. Future studies should include measures of arousal and anxiety in order to ascertain the impact of this negativity on their sleep difficulties. In fact, as previously suggested by Schredl (2009a), the apprehension of having negative dreams, including nightmares, could unconsciously exacerbate sleep onset difficulties in insomnia and the occurrence of negative dreams during the night could possibly wake them up more frequently, resulting in difficulties falling back asleep. This hypothesis remains to be tested since dream content linked to spontaneous awakenings during the night has not been measured yet. Our investigation failed to find significant group difference on all negative variables (aggressions, misfortunes, failures and negative emotions) and the majority of positive ones (friendliness, good fortunes and successes) when analyzed individually. These observations

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concur with previous research (Freedman & Sattler, 1982), which found no differences in content of sleep onset dreams between GSCs and patients with PI. Together these results suggest that the negative consequences usually encountered by patients with PI during the day, as well as their tendency for rumination (Morin et al., 2011), are not reflected in dreams through individual dream content per se, but through a more generalized negative oneiric content. That said, the dreams of GSCs tended to contain more positive emotions than those of patients with PI, which is in tune with the continuity hypothesis (Domhoff, 2010). Apart from the elevated negative content overall, positive emotions in dreams might be the only single variable that could be used to help differentiate patients with PI from GSC. The overall lack of difference between insomnia sufferers and controls, compared to previous studies on dream activity, could be due to the method used for dream collection in the present study, which has been previously shown to be feasible with PI without interfering too much with their sleep per se (Pérusse, De Koninck, & Bastien, 2015). Previous research has mostly relied upon dream diaries and questionnaires completed at home (Antrobus & Saul, 1980; Ohayon et al., 1997; Pagel & Shocknesse, 2007; Schredl et al., 1998). These methods are likely to increase the probability of intrusions and decrease recall capacity (Domhoff, 2003), compromising their representativeness. These methods also result in a lower number of dreams recalled per participant, which could lead, once more, to representativeness issues. In fact, to ensure representativeness of dream content, participants should report more than one dream occurring over more than one night. Alternatively, since the sample size used in the present study was relatively small, the study should be replicated with a larger sample so to increase statistical power. Results from the mood checklist revealed that patients with PI subjectively evaluated their dreams as being more negative than GSCs did. This higher subjective negativity in dream

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content of patients with PI could be a result of their daily negative attitude towards sleep difficulties and their associated consequences which again is consistent with the continuity hypothesis. As for dream recall frequency, contrary to our expectations, general dream and nightmare recall frequencies, measured by a questionnaire, were similar between groups. These results are not consistent with the majority of previous studies also using questionnaires in which a higher prevalence of nightmares in insomnia was reported. Our observations might be explained by the nature of nocturnal awakenings. Instead of having numerous awakenings during the night, which would enhance memory consolidation of the dream content, our patients with PI might have experienced few awakenings but with a longer duration, therefore not increasing dream recall frequency. On the other hand, as expected during in-lab dream collection, although patients with PI tended to have a higher dream recall frequency, the intergroup comparison was not significant, which might be explained by the systematic awakenings of participants in REM sleep. Finally, the relationship between negative dream content and sleep quality was studied. We suggested that a negative association would exist between sleep efficiency and negative dream content for patients with PI, but not for GSC. As expected, the objective SE was significantly related to negative dream content in the former group, showing that a low SE was linked to a higher amount of negative elements in dreams. Again additional measures of arousal would be needed to examine the nature of this association further. Nevertheless this finding suggests that the negative experience of recalling negatively perceived dreams may contribute to the exacerbation of sleep difficulties in patients with PI.

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To conclude, even though the above results should be interpreted within the limitations of the present study, such as the relatively small sample size, they suggest that dream activity, especially dream content and its relationship with sleep quality, need to be further explored to better understand its potential link to hyperarousal in insomnia. If further studies do confirm the negative character of the dreaming experience in insomnia, therapeutic interventions used to reduce nightmares and increase the positive content of dreams may prove useful in the treatment of this sleep disorder. The relatively small sample size prevented us from dividing patients with PI according to types. Future studies with larger sample sizes should subtype PIs into two distinct groups: psychophysiological insomnia sufferers and paradoxical insomnia (sleep misperception) sufferers since these two types appear to display different levels of hyperarousal (Bastien et al., 2013). These distinctions will help characterizing dream activity in different types of insomnia in order to determine its potential role in hyperarousal. Acknowledgements We would like to thank Josée Savard for her intellectual input, Alexandre Gaucher for PSG analysis, Jessica Lebel for dream transcription and all research assistants who helped in data entry and night monitoring. The present study was also made possible by funds from the CIHR to CHB (49500 and 86571). References American Academy of Sleep Medicine (2005). International classification of sleep disorders – Second Edition. Darien, Illinois: American Academy of Sleep Medicine. American Academy of Sleep Medicine (2014). International classification of sleep disorders – Third Edition. Darien, Illinois: American Academy of Sleep Medicine.

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American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders (5th Edition). Arlington, VA: American Psychiatric Publishing. Antrobus, J. S., & Saul, H. N. (1980). Sleep onset: subjective behavioral and electroencephalographic comparisons. Waking Sleep, 4, 259-270. In Schredl, M. (2009). Dreams in patients with sleep disorders. Sleep Medicine Review, 13(3), p. 216. Bastien, C. H. (2011). Insomnia: Neurophysiological and neuropsychological approaches. Neuropsychological Review, 21(1), 22-40. Bastien, C. H., Turcotte, I., St-Jean, G., Morin, C. M., & Carrier, J. (2013). Information processing varies between insomnia types: Measures of N1 and P2 during the night. Behavioral Sleep Medicine, 11(1), 56-72. Bastien, C. H., Vallières, A., & Morin, C. M. (2001). Validation of the Insomnia Severity Index as an outcome measure for insomnia research. Sleep Medicine, 2, 297-307. Beaulieu-Bonneau, S., LeBlanc, M., Mérette, C., Dauvilliers, Y., & Morin, C. M. (2007). Family history of insomnia in a population-based sample. Sleep, 30(12), 1739-1745. Beck, A. T., & Steer, R. A. (1993). Beck Anxiety Inventory Manual. San Antonio, TX: Psychological Corporation. Beck, A. T., Steer, R. A., & Brown, G. K. (1996). Manual for Beck Depression Inventory II (BDI-II). San Antonio, TX: Psychology Corporation. Cory, T. L., & Ormiston, D. W. (1975). Predicting the frequency of dream recall. Journal of Abnormal Psychology, 84(3), 261-266. De Koninck, J. (2012). Sleep, Dreams and Dreaming. In C. Morin & C. Epsie (Eds). Oxford Handbook of Sleep and Sleep Disorders. (pp. 150-171). New York: Oxford University Press. Domhoff, G. W. (2003). The scientific study of dreams: Neural networks, cognitive development, and content analysis. Washington, DC: American Psychological, Association Press. Domhoff, G. W. (2010). Dream content is continuous with waking thought, based on preoccupations, concerns, and interests. Sleep Medicine Clinics, 5, 203-215. Ermann, M. Die Traumerinnerung bei Patienten mit psychogenen Schlafstör-ungen: Empirische Befunde und einige Folgerungen für das Verständnis des Träumens. In: Leuschner W, Hau S, editors. Traum und Gedächtnis: Neue Ergebnisse aus psychologischer, psychoanalytischer und neurophysiologischer Forschung. Münster: LIT Verlag; 1995. P. 165-186. In Schredl, M. (2009). Dreams in patients with sleep disorders. Sleep Medicine Review, 13(3), p. 216.

Page 21 of 30

REM DREAMS AND INSOMNIA

22

Ermann, M., Peichl, J., & Pohl, H. (1993). Spontanerwachen und Träume bei Patienten mit psychovegetativen Schlafstörungen. Psychother. Psy-chosom., 43, 333-340. In Feige, B., AlShajlawi, A., Nissen, C., Voderholzer, U., Hornyak, M., Spiegelhalder, K., … Riemann, D. (2008). Does REM sleep contribute to subjective wake time in primary insomnia? A comparison of polysomnographic and subjective sleep in 100 patients. Journal of Sleep Research, 17(2), p. 188. Freedman, R. R., & Sattler, H. L. (1982). Physiological and psychological factors in sleep onset insomnia. Journal of Abnormal Psychology, 91(5), 380-389. Fortier-Brochu, E., Beaulieu-Bonneau, S., Ivers, H., & Morin, C. M. (2012). Insomnia and daytime cognitive performance: a meta-analysis. Sleep Medicine Reviews, 16(1), 83-94. Germain, A., & Nielsen, T. A. (2003). Sleep pathophysiology in posttraumatic stress disorder and idiopathic nightmare sufferers. Biological Psychiatry, 54(10), 1092-1098. Goodenough, D. R., Lewis, H. B., Shapiro, A., Jaret, L., & Sleser, I. (1965). Dream reporting following abrupt and gradual awakenings from different types of sleep. Journal of Personality and Social Psychology, 56, 170-179. Grenier, J., Cappeliez, P., St-Onge, M., Vachon, J., Vinette, S., Roussy, F., … De Koninck, J. (2005). Temporal references in dreams and autobiographical memory. Memory and Cognition, 33(2), 280-288. Hall, C., & Van de Castle, R. L. (1966). The content analysis of dreams. New York: AppletonCentury-Crofts. Hall, C. S., & Nordby, V. J. (1972). The individual and his dreams. New York: New American Library. Hantsoo, L., Khou, C. S., White, C. N., & Ong, J. C. (2013). Gender and cognitive-emotional factors as predictors of pre-sleep arousal and trait hyperarousal in insomnia. Journal of Psychosomatic Research, 74(4), 283-289. Koulack, D., & Goodenough, D. R. (1976). Dream recall and dream recall failure: An arousalretrieval model. Psychological Bulletin, 83(5), 975-984. Li, S. X., Zhang, B., Li, A. M., & Wing, W. K. (2010). Prevalence and correlates of frequent nightmares: a community-based 2-phase study. Sleep, 33(6), 774-780. Morin, C. M. (1993). Insomnia: psychological assessment and management. New York: Guilford Press. Morin, C. M., LeBlanc, M., Bélanger, L., Ivers, H., Mérette, C., & Savard, J. (2011). Prevalence of insomnia and its treatment in Canada. Canadian Journal of Psychiatry, 56(9), 540-548.

Page 22 of 30

REM DREAMS AND INSOMNIA

23

Ohayon, M. M. (2002). Epidemiology of insomnia: What we know and what we still need to learn. Sleep Medicine Reviews, 6(2), 97-111. Ohayon, M. M., Morselli, P. L., & Guilleminault, C. (1997). Prevalence of nightmares and their relationship to psychopathology and daytime functioning in insomnia subjects. Sleep, 20(5), 340348. Pagel, J. F., & Shocknesse, S. (2007). Dreaming and insomnia: Polysomnographic correlates of reported dream recall frequency. Dreaming, 17(3), 140-151. Perlis, M. L., Giles, D. E., Mendelson, W. B., Bootzin, R. R., & Wyatt, J. K. (1997). Psychophysiological insomnia: the behavioural model and a neurocognitive perspective. Journal of Sleep Research, 6(3), 179-188. Pérusse, A. D., De Koninck, J., & Bastien, C. H. (2015). Insomnia sufferers can tolerate laboratory REM sleep dream collection which may improve their sleep perception. International Journal of Dream Research, 8(1), 54-57. Rechtschaffen, A., & Kales, A. (1968). A manual of standardized terminology, techniques, and scoring system for sleep stages of human subjects. Los Angeles: Brain Information Service/Brain Research Institute, University of California. Schredl, M. (1991). Traumerinnerungshäufigkeit und trauminhalt bei schlafgestörten, psychiatrischen patienten und gesunden (diploma thesis). University of Mannheim, Mannheim. In Feige, B., Al-Shajlawi, A., Nissen, C., Voderholzer, U., Hornyak, M., Spiegelhalder, K., … Riemann, D. (2008). Does REM sleep contribute to subjective wake time in primary insomnia? A comparison of polysomnographic and subjective sleep in 100 patients. Journal of Sleep Research, 17(2), p. 188. Schredl, M. (2009a). Nightmare frequency in patients with primary insomnia. International Journal of Dream Research, 2(2), 85-88. Schredl, M. (2009b). Dreams in patients with sleep disorders. Sleep Medicine Reviews, 13(3), 215-221. Schredl, M., Schãfer, G., Weber, B., & Heuser, I. (1998). Dreaming and insomnia: Dream recall and dream content of patients with insomnia. Journal of Sleep Research, 7(3), 191-198. Schredl M., & Wittmann L. (2005). Dreaming: a psychological view. Schweizer archiv für neurologie und psychiatrie,156(8), 484- 492. Schredl, M., Wittmann, L., Ciric, P., & Götz, S. (2003). Factors of home dream recall: A structural equation model. Journal of Sleep Research, 12(2), 133-141.

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REM DREAMS AND INSOMNIA

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Sheehan, D. V., Lecrubier, Y., Sheehan, K. H., Amorim, P., Janavs, J., Weiller, E., … Dunbar, G. C. (1998). The Mini-International Neuropsychiatric Interview (M.I.N.I.): The development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10. The Journal of Clinical Psychiatry, 59(Suppl. 20), 22-33. Van de Laar, M., Verbeek, I., Pevernagie, D., Aldenkamp, A., & Overeem, S. (2010). The role of personality traits in insomnia. Sleep Medicine Reviews, 14(1), 61-68. Wilson, B., Cockburn, J., Baddeley, A., & Hiorns, R. (1989). The development and validation of a test battery for detecting and monitoring everyday memory problems. Journal of Clinical and Experimental Neuropsychology, 11(6), 855–870.

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Appendix Table 1 Table 1 Means (SD) of socio-demographic, psychological and memory functioning data Patients with PI n = 12

GSC n = 12

t value

p

d

χ2 = 0 1.0 Gender ----Male 8 8 Female 4 4 Age (years) 37.5(4.3) 37.3(4.7) .1 .9 .04 Education (years) 16.8(2.3) 16.4(3.3) .3 .8 .12 Insomnia duration (years) 21.1(15.9) ---------4.6 < .001** ----Questionnaires ISI (severity score) 7.8(1.9) 2.9(1.7) 2.70 6.6 < .001** BDI 6.5(4.0) 6.2(7.8) .1 .9 .05 BAI 4.8(2.9) 5.3(4.7) -.3 .8 .11 General dream recall 3.7(2.0) 3.6(1.6) U=53.5 .7 .07 General nightmare recall 1.8(1.2) 1.8(1.1) U=60.0 1.0 .04 Memory functioning Global Memory Index 99.8(8.8) 99.0(15.1) .2 .9 .07 SI (scale score) 9.8(2.0) 10.5(2.7) -.8 .5 .32 SD (scale score) 10.3(2.5) 10.6(4.5) -.2 .8 .09 Note. ** p ≤ 0.001; Primary insomnia (PI); Good sleepers controls (GSC); Insomnia Severity Index (ISI); Beck Depression Inventory (BDI); Beck Anxiety Inventory (BAI); Story Immediate Recall (SI); Story Delayed Recall (SD).

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Table 2 Table 2 Means (SD) of objective and subjective sleep parameters of ambulatory nights (2 & 4) Patients with PI n = 12 N2 N4

GSC n = 12

F

p

d

N2

N4

Objective sleep parameters 15.9 (13.1) 14.3 (10.9) SOL 82.0 (64.7) 51.5 (22.9) WASO 401.8 (73.9) 424.3 (47.2) TST 96.4 (61.2) 62.4 (27.4) TWT 80.8 (11.3) 87.0 (5.1) SE (%)

16.9 (15.9) 41.2 (19.7) 447.2 (64.1) 58.1 (24.9) 88.5 (4.6)

15.8 (10.9) 34.0 (20.2) 433.0 (47.1) 49.8 (21.7) 89.8 (3.4)

.1 5.6 1.5 4.1 5.5

.8 .03* .2 .06 .03*

.004 .23 .08 .18 .22

Subjective sleep parameters 17.3 (8.9) SOL 92.2 (82.1) WASO 368.2 (61.6) TST 108.4 (86.5) TWT 75.6 (11.8) SE (%)

11.8 (9.9) 16.2 (13.0) 458.1 (63.8) 28.0 (20.3) 91.8 (6.1)

12.0 (7.3) 15.6 (19.3) 444.6 (47.0) 27.5 (22.4) 92.7 (5.5)

2.9 15.8 16.9 15.1 22.5

.1 .001** .001** .001** <.001**

.12 .43 .45 .42 .52

21.2 (22.1) 47.2 (37.2) 398.2 (30.3) 61.3 (39.3) 83.7 (7.0)

Note. * p ≤ 0.05; ** p ≤ 0.001; Primary insomnia (PI); Good sleepers controls (GSC); Sleep onset latency (SOL); Wake after sleep onset (WASO); Total sleep time (TST); Total wake time (TWT); Sleep efficiency (SE).

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Table 3 Table 3 Means (SD) of objective and subjective sleep parameters of laboratory nights (3 & 5) Patients with PI n = 12 N3 N5

GSC n = 12 N3

N5

F

p

d

Objective sleep parameters 15.6 (12.7) SOL 122.8 (68.2) WASO 360.6 (79.0) TST 138.4 (71.8) TWT 72.2 (15.1) SE (%)

13.6 (8.9) 122.3 (66.8) 372.8 (83.8) 135.9 (70.6) 73.2 (14.7)

9.1 (6.1) 79.9 (39.2) 404.5 (46.4) 89.0 (41.5) 81.9 (8.5)

16.6 (16.4) 84.5 (46.7) 390.6 (41.9) 101.1 (53.9) 79.8 (10.4)

.2 3.2 1.4 3.1 2.7

.7 .1 .3 .1 .1

.01 .13 .06 .12 .11

Subjective sleep parameters 24.6 (15.4) SOL 105.2 (95.9) WASO 339.2 (118.3) TST 107.5 (78.7) TWT 71.7 (15.8) SE (%)

34.6 (31.1) 90.6 (106.2) 365.8 (126.7) 93.7 (58.2) 77.8 (10.2)

14.6 (9.1) 28.1 (17.4) 448.6 (48.6) 42.7 (21.4) 91.7 (6.4)

18.0 (13.6) 26.5 (25.0) 440.9 (46.6) 44.4 (34.3) 89.8 (8.0)

4.5 6.5 5.8 9.2 14.8

.05* .02* .03* .01* .001**

.17 .24 .22 .30 .41

Note. * p ≤ 0.05; ** p ≤ 0.001; Primary insomnia (PI); Good sleepers controls (GSC); Sleep onset latency (SOL); Wake after sleep onset (WASO); Total sleep time (TST); Total wake time (TWT); Sleep efficiency (SE).

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Table 4 Table 4 Paired sample t-tests for mean (SD) of negative oneiric elements and positive oneiric elements as a whole calculated from the Hall & Van de Castle scale (1966) Negative elements Positive elements .99 (.52) .41 (.27) Patients with PI (n = 12) .95 (.50) .62 (.42) GSC (n = 12) .97 (.50) .51 (.36) All participants (n = 24) Note. ** p ≤ 0.001; Primary insomnia (PI); Good sleepers controls (GSC).

t value 4.50 1.76 3.98

p .001** .11 .001**

d 1.31 .50 .82

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Table 5 Table 5 Means (SD) of objective dream content per dream from the Hall & Van de Castle scale (1966) Patients with PI n = 12 111.97 (57.19) 2.54 (1.09) .99 (.52)

GSC n = 12 150.08 (65.70) 3.07 (1.12) .95 (.50)

# of words Characters Negative variables Aggressions .34 (.29) .35 (.28) Failures .11 (.16) .04 (.06) Misfortunes .38 (.30) .33 (.29) Negative emotions .16 (.20) .24 (.33) .41 (.27) .62 (.42) Positive variables Friendliness .32 (.28) .43 (.32) Success .02 (.05) .07 (.15) Good fortunes .06 (.12) .03 (.08) Positive emotions .01 (.04) .09 (.13) Note. Primary insomnia (PI); Good sleepers controls (GSC).

t value

p

d

-1.52 -1.18 .17

.14 .25 .87

.62 .48 .08

-.13 1.61 .44 -.73 -1.44 -.90 -1.02 .70 -2.03

.90 .12 .67 .48 .17 .38 .32 .49 .06

.04 .58 .17 .29 .59 .37 .45 .29 .83

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Table 6 Table 6 Means (SD) of subjective evaluation of emotional content in dreams from the mood checklist Patients with PI GSC p d n = 12 n = 12 Joy 1.97 (.99) 2.50 (1.06) .52 .006* Happiness 1.96 (.98) 2.37 (1.11) .39 .03* Apprehension 1.61 (.97) 1.57 (.81) .91 .04 Anger 1.34 (.74) 1.21 (.62) .21 .19 Sadness 1.19 (.57) 1.11 (.31) .82 .17 Confusion 1.46 (.76) 1.73 (1.00) .16 .30 Anxiety 1.57 (.87) 1.43 (.78) .34 .17 Fear 1.34 (.68) 1.27 (.65) .34 .11 Quality of recall 2.44 (1.00) 2.73 (1.05) .10 .28 Degree of vividness 2.70 (.94) 3.21 (.80) .58 .003* Pleasant content 2.14 (1.00) 2.61 (.99) .47 .01* Unpleasant content 1.60 (.95) 1.59 (.83) .72 .01 Note. * p ≤ 0.05; Primary insomnia (PI); Good sleepers controls (GSC).

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