Similar to dissociation, sleep related experiences (SRE’s) include a variety of nocturnal altered-consciousness phenomena, such as nightmares, dreams with narcoleptic characteristics, recurring dreams, dream recall, vivid dreams, problem-solving dreams, dreams confused with reality, and lucid dreams (8,9). People suffering from nightmares report an overall richness in their dream life and are more likely to be affected by their dreams the following day (10-12). Several studies have reported a positive association between frequency of nightmares and dissociative disorders, schizophrenia, and PTSD (13,14). It has also been reported that more than half of the patients with dissociative disorders also had a diagnosis of nightmare disorder (13).
Given their dreamlike properties, one might suspect a robust link between dissociative symptoms of derealization, depersonalization, and amnesia and SRE’s. Watson defined SREs as ”dissociations of the night” and demonstrated that there is a positive association between self-report measures of SREs and dissociative experiences (9, 15, 16). In the latter studies,
SRE’s have been measured with Iowa Sleep Experiences scale (ISES, 9, 15) and dissociative experiences were measured with the well-validated measure of Dissociative Experiences Scale (DES) (16). ISES is a self-report questionnaire measuring general sleep experiences and lucid dreaming. Association of ISES, particularly ISES General Sleep Experiences scale with dissociative experiences and schizotypy is a well-established finding that has been consistently found in many studies, mainly with non-clinical populations (15,17-20).
So far, three views have been developed to explain the overlap between unusual daytime and nighttime experiences: The first view explains this overlap by abnormalities of the sleep- wake cycle. According to this view, errors or overlaps that occur during the shift from sleep to wakefulness (or vice versa) cause a blurring of the boundaries between these states and underlies the overlap between daytime and nighttime experiences (22). To explain the association between sleep-related experiences and dissociation, Watson (9), on the basis of his finding, speculated that dissociative symptoms might be enhanced by labile sleep-wake cycles, such given that individuals with these symptoms easily pass from normal waking mentation state to dream-like states. It has also been hypothesized that individuals who are prone to dissociation have an inherited or acquired hypersensitivity of the cholinergic system that allows them to easily shift from waking to dreamlike states (23). The second view emphasizes the role of stress and trauma. Traumatic experiences are known to disrupt both daytime and nighttime experiences since trauma usually triggers day time dissociations, i.e. flashbacks and sleep disturbances i.e. nightmares (Gershuny & Thayer, 1999; Harvey et al., 2003). The final view highlights the importance of underlying personality traits. More specifically, absorption and fantasy proneness are found to be the main aspects of personality that have been found to be related to the overlap between day-time and night-time experiences ((Fassler et al., 2006; Giesbrecht & Merckelbach, 2006). In a recent publication, Koffel reviewed the evidence for all three models and concluded that any comprehensive theory of daytime and nighttime symptoms will most likely need to invoke aspects of all three models (8). Furthermore, Koffel argues that the overlap between unusual sleep experiences, schizotypy and dissociation is underlied by a common domain referred as “unusual cognitions and perceptions.
By focusing on the first view which conceptualizes unusual day-time and nigh-time experiences arising from abnormalities in the sleep-wake cycle, the present study considers the role of sleep quality and its relation to unusual sleep experiences and dissociation. To our knowledge, no studies so far have considered the role of general sleep quality in the context of the overlap between unusual day-time experiences of dissociation and schizotypy and the unusual night-time experiences.
There is no doubt that general sleep experiences may depend on the general quality of sleep. Based on the previous literature suggesting that dissociation and unusual sleep experiences are underlied by the common domain of “unusual cognitions and perceptions”, we also expect to find a positive association between dissociation and general sleep quality.
Furthermore, the predictive value of dissociative symptoms and of general sleep quality on general sleep experiences will be examined. More specifically, we aim to replicate the well-established association between dissociation and sleep experiences; and to extend the previous findings on this association by considering the role of sleep quality. To test our hypotheses, we used self-report measures of dissociation, general sleep experiences and general sleep quality in a Turkish undergaduate sample .
Participants were 127 undergraduate students enrolled at the University of Bogazici. After the study protocol was throughly explained, informed consents were obtained from the participants. Sixty-seven (53%) of the participants were females and sixty (47%) of them were males, general mean age was 23.07 years (SD=2.12; range: 19-29 years).
Dissociative Experiences Scale (DES):
The DES is a self-report scale asking respondents to indicate the extent to which they experience 28 dissociative phenomena in daily life on 100 mm visual-analog scales. Examples of such phenomena include feelings of depersonalization, derealization, and psychogenic amnesia. A subset of eight DES items forms the Dissociative Experiences Scale Taxon (DES-T) (24) which is thought to be especially sensitive to pathological dissociation. DES-T scores can be obtained by averaging across DES items 3, 5, 7, 8, 12, 13, 22, and 27.
Following Watson (9), we used Carlson et al.’s (25)three factor (e.g., amnesia, absorption/imaginative involvement, depersonalization/ derealization) analysis of the DES. The Amnesia subscale (8 items; e.g., “Some people have the experience of finding themselves in a place and having no idea how they got there”), the Depersonalization and Derealization (Depersonalization) subscale (6 items; e.g., “Some people have the experience of feeling that other people, objects, and the world around them are not real”), and the Absorption and Imaginative Involvement (Absorption) subscale (9 items; e.g., “Some people find that when they are watching television or a movie they become so absorbed in the story that they are unaware of other events happening around them”).
The DES has adequate validity and reliability in both normal and clinical samples (26). The Turkish version of the scale has satisfactory reliability and validity with indices comparable to its original form (27,28).
Iowa Sleep Experiences Scale (ISES): The ISES (9,15)consists of 18 questions asking the respondent to rate the frequency of various sleep- and dream-related experiences (e.g., ”A dream helped me to solve a current problem or concern.”, ”Lying in bed, I sense the presence of someone who actually isn_t there.”) on a 7 point-Likert scale (anchors: 1= never; 7= several times a week). The ISES contains two separate subscales that measure general sleep experiences (GSE, 15 items; Cronbach_s I± = 0.81) and lucid dreaming (LD, 3 items; Cronbach I± = 0.77), respectively. These subscales show a moderate correlation with correlation coeefficients around 0.40, indicating that they measure distinct, but related constructs (9). A mean score can be obtained by averaging across all items.
The ISES is the only reliable and valid measure of the wide range of nocturnal altered-consciousness experiences. However, the validity and reliability of this scale were not established for the Turkish version. As described below, the translation of the ISES were made by the authors of the present study. Cronbach’s alpha was 0.87 for ISES total score, 0.86 for GSE and 0.83 for LD in this study. Finally, for the present sample, Kaiser Meyer Olkin measure of sampling adequacy was 0.83.
The repeated forward-backward translation procedure was adopted as it is most commonly quoted in the adaptation and translation process (29). In this procedure a forward translation is made from the source original language to the target new language. The target language version is then translated back into the source language and compared to the original version. Errors in the target language version are identified through changes in meaning that arise in the back translation. The procedure was broadly divided into four phases. Phase 1 was to make four Turkish translated versions of the original scale and unify these four. Phase 2 was to produce a back-translated version. Phase 3 was to check the equivalence between the original scale and the back-translated version. Phase 4 was to continue forward and backward translation until satisfactory equivalence was agreed.
The Pittsburgh Sleep Quality Index (PSQI), which is an instrument with previously established reliability and validity (30), was administered to assess sleep quality during the previous month. The PSQI consists of 19 self-rated questions. These 19 items are grouped into seven component scores, each weighted equally on a 0-3 scale. The components are subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, use of sleeping medications, and daytime dysfunction. The seven component scores are then summed to yield a global PSQI score, which has a range of 0-21; higher scores indicate worse sleep quality. Turkish version of the PSQI was evaluated by Agargun et al (31).
Mean DES, global PSQI, ISES total scores were 12.12 (SD=9.25), 7.89 (SD=2.36) and 2.29 (SD=0.80), respectively. The mean DES score corresponds with values that previous studies reported for student samples (32). Table 1 shows subscale and total score means of the DES, PSQI and ISES. Table 2 presents Pearson correlations between DES, ISES and PSQI subscales and total scores.
All subscale and total scores of the DES were moderately correlated with total ISES and ISES GS subscale scores. Correlations varied between .35 to .57, p <.001. PSQI total scores as well as the scores from PSQI subscales of sleep disturbances, use of sleeping medication and daytime dysfunction was weakly correlated with total ISES scores and ISES general sleep experiences subscale scores. Correlations varied from from .22 to .35, p<.05.. On the other hand, DES and PSQI total scores and subscale scores were not correlated with the lucid dreaming subscale of ISES, implying that the correlations in the total scores were mainly derived by the general sleep experiences subscale..
DES total scores were weakly correlated with the total PSQI scores (r=.29, p < .05) and with the scores from PSQI subscales of sleep disturbances, use of medication and day time dysfunction. The results were similar to DES total scores for DES taxon scores except for the fact that DES taxon scores were not significantly related to the use of sleeping medication subscale of PSQI. Correlations varied from .18 to .29, p < .05(see table 3).
In order to observe the predictive value of dissociation and general sleep quality on general sleep experiences, GS subscale of ISES was regressed on the DES subscales of absorption and depersonalization and on the PSQI subscales of sleep disturbances and use of sleeping medication. The latter stepwise regression conducted with maximum likelihood method revealed that both subscales of both measures are significant and together these subscales account for 37% of the variance in general sleep experiences subscale of ISES (see table 4).
The different types of dreams and nocturnal experiences described above may all be conceptualized as ”dissociations of the night” (9) or nocturnal altered-consciousness phenomena(21). In this study we found significant positive correlations between ISES, ISES general sleep experiences, DES Taxon, DES total and subscales. No association was found between lucid dreaming and DES total and subscale scores. Most of the research examining the overlap of sleep, dissociation, and schizotypy has been conducted using the ISES (8,9). Association of the ISES General Sleep Experiences scale with dissociation and schizotypy is a well-established finding that has been confirmed in many studies. Several studies have found that the DES correlates significantly with the ISES General Sleep Experiences scale, but not with the ISES Lucid Dreaming scale (17-19). Previous findings are replicated in the present study (9,15,18,20).
Moreover, linear regression analyses showed that especially the symptoms of absorption and depersonalization may be at the heart of the link between the ISES and dissociation. There seem to exist a modicum of continuity of waking and sleep-related experiences as suggested by Watson and recently by Koffel (20).
The studies examining sleep disorders and associations are scare in the literature. Schenck et all. (33) found that 5% of the patients from a sleep disorder clinic also have dissociative Identity Disorder either in the clinical and sub-clinical levels (34,35). Another commonality between pathological dissociation and nocturnal experiences is the that patients diagnosed with Dissociative Identity Disorder (DID) have a high prevalence of nightmare disorder (13). More than half of the patients with dissociative disorders also had a diagnosis of nightmare disorder (13).
In the current study, we examined the relationship between general sleep quality (e.g. sleep duration, latency, disturbations, efficiacy etc.), dissociative experiences and SRE’s. Apart from replicating the well-established association between dissociation and unusual sleep experiences, in the present study we considered the relation of general sleep quality to dissociation. We found that some indices of sleeping problems like sleep disturbances, use of sleeping medication and day time dysfunction due to sleeping problems, were positively associated both with dissociation and general sleep experiences. However, subjective sleep quality, sleep latency and duration, as well as habitual sleep efficiency scores were not significantly associated with DES scores and ISES scores (see Table 2 and 3).
The linear regression analyses revealed that absorption and depersonalization symptoms of dissociative symptoms explain a considerable amount of variance in general sleep experiences. Sleep disturbances and use of sleeping medication (with DES Absorction and Depersonalization) as indicators of sleeping problems, were related to ISES General Sleep Experiences (Table 4). The general conclusion we draw from the present findings is that mainly sleep disturbances, but not the general sleep characteristics (like sleep duration, or latency) are associated with dissociation and unusual sleep experiences. Sleeping problems may cause abnormal rapid eye movement (REM) sleep. During REM sleep, cholinergic neurons are activated and blood flow shifts to the subcortical limbic structures, leading to a more basic level of processing, to a focus on internal stimuli, to nonlinear thoughts, and disruptions in memory (23). And sleeping problems, particulary those involving REM period can cause disruptions in memory and consciousness during wakefulness.
The present study is limited in the sense that the role of personality traits like schizotypy were not considered.Watson (9) suggested that the mechanism underlying the association between SREs and dissociative tendencies might be a personality trait, which determines the relative ease or difficulty with which psychological material can shift between different states of consciousness. Watson (9) provided evidence that SREs are related to schizotypal . Nevertheless, another personality trait referred as absorption and imaginative involvment have been included within the dissociation scale, and is found to be a strong predictor of unusual sleep experiences. A second limitation of the study is that it does not take into account the role of stress and previous trauma. Childhood trauma, particularly child maltreatment, has been repeatedly shown to be associated with dissociation (36,37), and therefore might be associated SRE’s as well (21). Future studies of the SRE’s should also consider the role of stress and trauma. A third limitation of the present study is that it is mainly based on self-report questionnaires from a non-clinical sample. Finally and most importantly, one should be careful to interpret the present findings in the sense that the conclusions drawn from the present study are mainly correlational, and any generalization on the causal mechanisms is not warranted.