The mechanisms of action underlying the efficacy of psychological nightmare treatments: A systematic review and thematic analysis of discussed hypotheses

Accepted Manuscript The mechanisms of action underlying the efficacy of psychological nightmare treatments: A systematic review and thematic analysis of discussed hypotheses Rousseau Andréanne, Belleville Geneviève PII:

S1087-0792(17)30113-2

DOI:

10.1016/j.smrv.2017.08.004

Reference:

YSMRV 1057

To appear in:

Sleep Medicine Reviews

Received Date: 1 June 2017 Revised Date:

6 August 2017

Accepted Date: 23 August 2017

Please cite this article as: Andréanne R, Geneviève B, The mechanisms of action underlying the efficacy of psychological nightmare treatments: A systematic review and thematic analysis of discussed hypotheses, Sleep Medicine Reviews (2017), doi: 10.1016/j.smrv.2017.08.004. 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.

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The mechanisms of action underlying the efficacy of psychological nightmare treatments : A systematic review and thematic analysis of discussed hypotheses

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Rousseau, Andréanne and Belleville, Geneviève* École de Psychologie, Université Laval, Québec, Canada

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*Corresponding author: École de Psychologie, Université Laval, Pavillon Félix-Antoine-Savard, Bureau 1116, 2325, rue des Bibliothèques, Québec (Québec), G1V 0A6 Canada,

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Tel: +1 418 656 2131x4226; fax: +1 418 656 3646

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E-mail address: [email protected]

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Abstract Studies of psychotherapeutic treatments for nightmares have yielded support for their effectiveness. However, no consensus exists to explain how they work. This study combines a systematic

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review with a qualitative thematic analysis to identify and categorize the existing proposed mechanisms of action (MA) of nightmare treatments. The systematic review allowed for a great number of scholarly publications on supported psychological treatments for nightmares to be identified. Characteristics of the

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study and citations regarding potential MAs were extracted using a standardized coding grid. Then,

thematic analysis allowed citations to be grouped under six different categories of possible MAs according

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to their similarities and differences. Results reveal that an increased sense of mastery was the most often cited hypothesis to explain the efficacy of nightmare psychotherapies. Other mechanisms included emotional processing leading to modification of the fear structure, modification of beliefs, restoration of sleep functions, decreased arousal, and prevention of avoidance. An illustration of the different variables involved in the treatment of nightmares is proposed. Different avenues for operationalization of these

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MAs are put forth to enable future research on nightmare treatments to measure and link them to efficacy measures, and test the implications of the illustration.

Keywords

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Abreviations

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Nightmares, psychological treatment, mechanism of action, efficacy

ERRT: Exposure, relaxation, and rescripting therapy; IRT: Imagery rehearsal therapy; MA: Mechanism of action; PTSD: Post-traumatic stress disorder

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The efficacy of psychological nightmare treatments is now supported by numerous studies; four meta-analyses have summarized their results, based on a total of 511 to 1285 participants (1-4). They combine data from many populations reporting recurring nightmares, either posttraumatic or idiopathic.

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Results showed that treatments have medium to large effect sizes on nightmare frequency, distress and intensity, sleep quality, insomnia, as well as symptoms of post-traumatic stress disorder (PTSD),

depression, and anxiety. Follow-ups showed continued improvement in nightmare frequency and PTSD

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symptoms after end of treatment. Overall, treatments with empirical support include the following in their protocol: exposure or systematic desensitization to the nightmare content, rescripting of the nightmare

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content, learning to become lucid while dreaming, and relaxation and breathing techniques (5). These promising findings in this emergent field of study must however be considered in light of some lacunas. First, the large range of empirically-supported nightmare treatment protocols with different names but similar components render the choice of which approach to favour unclear. As decried by Harb et al. (6), such studies in isolation may not build on prior research and advance the field (p.577). This

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multiplication of protocols could be the result of the lack of a theoretical model explaining efficacy of psychological nightmare treatments (6).

According to Kazdin (7), a mechanism of action (MA) is a process through which therapy

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produces a change; as opposed to outcome efficacy, it is ongoing and must be measured several times during therapy. Clear knowledge of how a treatment is efficacious could resolve the scattering of protocols

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by allowing for parsimony.

Several hypotheses have been put forth to explain the efficacy of nightmare treatments, but many

lack empirical support (8) and they differ according to treatments and authors. For example, IRT is a treatment in which the patient is asked to modify the script of his or her nightmare in order to give it a positive or neutral ending; this new script will be imagined visually each day at home. It has been posited that IRT owes its efficacy to the patient’s gain in his or her ability to control the stressful elements in his or her dreams (9). However, Exposure, relaxation, and rescripting therapy (ERRT) is a variant of IRT that includes an additional exposure component: patients are invited to write or imagine the nightmare script

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before rescripting it. According to the developers of ERRT, nightmares are fear stimuli that must be dissociated from the fear response through habituation (10). However, it has also been argued that exposure to nightmare content is not a necessary component, as IRT is efficacious while minimizing

very similar and have been shown to be efficacious.

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exposure (11). Thus, there is no consensus about the theory underlying these treatments, although both are

Given that no consensual theoretical model exists, the constructs used to explain treatment

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efficacy are poorly defined and different authors use varying terminology to refer to MAs. To our

knowledge, only one study had the main objective to operationalize and measure a MA. Germain et al.'s

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(9) study compared verbatim transcripts of nightmares to the new script their participants created in an IRT protocol. They observed that new scripts had more mastery elements and greater diversity of control modalities. These findings were interpreted as lending support to the idea of increased mastery in patients that could account for IRT's efficacy. However, their study protocol had only one measure time point and didn’t allow examination of whether this new sense of mastery was generalized outside therapy. More

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important is the limitation raised by Nappi et al. (8): to be demonstrated as a MA, mastery has to be associated to the efficacy of therapy,.

A theoretical model explaining nightmare creation and recurrence appears as a prerequisite to

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explain the efficacy of nightmare treatments. In the field of psychological nightmare treatments, there are two existing models, both focussing on maintenance factors. However, Spoormaker’s model (12) seems to

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explain only recurring nightmares, while Davis' model (10) has been developed to explain the ERRT protocol and is limited to an explanation of recurring posttraumatic nightmares. Although interesting, there are few references to these models in the literature and they do not bring clear conclusions as to the MAs of psychological nightmare treatments. Nielsen and Levin’s model (13-14) on the other hand is derived from fundamental research in the field of dreams and is well supported. This model stipulates that dreams’ function is to allow fear extinction, which could be done by the activation of the fear memory while dreaming, a process of recombination with non-fearful elements and regulation of the emotion expression by REM sleep. A nightmare would result from impairment in one of these three steps. This

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model has the advantage of explaining the function of all dream types; however, it doesn't lead to therapeutic recommendations and doesn't take into account nightmare treatment research. In summary, the field of psychological nightmare treatments lacks a comprehensive theoretical

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model. For this reason, there is little data on MAs, and knowledge advancement of nightmare treatments appears somewhat disorganized. A comprehensive model of nightmare treatments’ MAs could reduce confusion and help researchers elaborate and improve treatment protocols in a coherent and efficient way.

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Such a model should be based on previous research, mainly MA hypotheses developed in the field of nightmare treatments. This could be viewed as a meta-ethnographic work, as it has the objective to review

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and synthesize qualitative results about the beliefs, opinions or conceptions of a sub-group of people (15). For this study, the targeted sub-group of people is researchers in the field of psychological nightmare treatments, and the data analysed are the verbatim sentences about MAs found in their publications. This review of the current hypotheses on MAs discussed in the literature will be organised according to a qualitative thematic analysis, i.e., grouping the many labels that are used to discuss similar concepts and

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critiquing them in the light of available evidence. This synthesis method has the potential to provide a higher level of analysis, generate new research questions and reduce duplication of research (15). This study combines a systematic review with a qualitative thematic analysis to identify and

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categorize the existing explanations about MAs in studies of nightmare treatments. The explored research questions are: 1) what are the proposed MAs?; 2) what is the dominant MA theory?; 3) are there MAs

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associated with some treatments more than others or can a single MA explain the efficacy of more than one therapy?; 4) what are the empirical supports for these MAs? This discussion will allow these MAs to be integrated through the elaboration of an explanatory illustration of psychological nightmare treatments’ efficacy, in coherence with Nielsen and Levin' model of nightmares (13-14), and completing the ones of Spoormaker (12) and Davis (10).

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Method The methodology and style of reporting of results used in the present research were developed

Guidelines for qualitative research articles in medicine (17).

Literature search.

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according to Preferred reporting items for systematic reviews and meta-analysis guidelines (16) and

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To compile studies that refer to a MA of a nightmare treatment, a systematic review was

performed. The search was performed with the keywords « nightmare AND therapy OR treatment » in

studies not previously identified.

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PsycINFO, MedLine and ProQuest databases. Reference lists of included studies were screened for new

Inclusion criteria were: 1) publication is about a psychological nightmare treatment included in the list of evidence-based treatments found in Aurora et al. (5): IRT, systematic desensitization, Progressive deep muscle relaxation, ERRT, Sleep dynamic therapy, Lucid-dreaming therapy, self-exposure therapy

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(similar treatments with different labels, such as hypnosis used in order to modify the end of the nightmare (18) were also included); 2) the study is a scientific publication found in a journal or a book, theoretical or empirical, describing a nightmare treatment or presenting data about treatment efficacy, moderators or

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mediators; 3) the study was published in English or French; 4) year of publication was 2016 or earlier. Excluded from these criteria were: audio documents, posters, symposiums, documents destined to the

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public, treatment manuals, publications lacking information on the therapy or where treatment did not target nightmares specifically (e.g., exposure therapy for PTSD). After reading eligible publications, those that failed to mention at least one hypothesis of a nightmare therapy MA were withdrawn.

Data extraction and operationalization. Each eligible publication was reviewed by the first author. A data coding form was developed to ensure accuracy and consistency in the data collection process. The following information was extracted from each study: 1) identification, i.e., authors and publication date; 2) study protocol; 3) sample

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characteristics, i.e., size, population (military/veterans, sexually assaulted victims, general population, minors or persons with an intellectual deficiency) and type of nightmares (post-traumatic or idiopathic); 4) treatment's label and component(s); and 5) presumed MA (the direct citation of one or more sentences was

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transcribed in the coding form). A presumed MA was identified when authors discussed processes explaining the efficacy or the rationale of the treatment. To be included, the presumed MA had to explain the effect on nightmares specifically, and not on other symptoms, such as depression, PTSD or quality of

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life.

The following were not retained as presumed MAs: 1) enumeration of possible MA without clear

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links to specific data or treatment; 2) the statement that the MA is unknown; 3) a direct citation of another author's hypothesis already included in the review; 4) how a component had facilitated therapy - a moderator variable; and 5) a hypothesis that the author refutes.

In order to simplify results, IRT, ERRT, Imagery rescripting and exposure therapy, Sleep intervention for PTSD and focus-orienting dreamwork therapies were grouped under the term "therapies

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based on rescripting". Desensitization, in vivo exposure, self-exposure and exposure were grouped under the term "exposure". Other therapies retained their original label. Although ERRT and IRET contain a form of exposure, this component treatment is not realised under usual principles of prolonged exposure;

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these treatments were considered more similar to IRT in their content (rescripting a nightmare), hence their inclusion in the therapies based on rescripting.

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Qualitative data analysis.

Citations were coded in order to determine the kind of justification supporting the MA. An

empirical demonstration meant that a variable was identified as a possible MA a priori and measured in the study. A posteriori observations designated explanations derived from observations or results from efficacy studies that were not identified as MA variables in the protocol. Finally, explanations could be based on theoretical grounds.

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A qualitative thematic analysis was performed by the first author to categorize the collected citations under categories referring to different MAs. Each citation was given one or more keywords representing the supposed MA exposed in the sentence. Similar keywords were then grouped to form main

category in order to summarize all the citations they encompass.

Inter-rater agreement.

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categories of MA. A definition of the MA and its implication on theory of nightmares was created for each

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After MA categories were created, a second evaluator, an undergraduate psychology student, was given the definitions of MA categories and a list of all the included citations. Each citation was reassigned

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to a category; the results were compared in biweekly meetings and discrepancies were resolved through discussion. Overall agreement between raters was 76.7%.

Results

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Search results and characteristics of studies.

A flow chart summarizing the search results, characteristics, references of the studies included in this review can be found in supplementary data. On the 64 studies included in this review, there were six

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reviews, two meta-analyses, 21 case studies, 21 randomized controlled trials (RCT), 10 uncontrolled studies, and four theoretical publications. The majority were about IRT and ERRT, some were about

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exposure and lucid dreaming, and some studied treatments otherwise labelled. Studies were published between 1967 and 2016.

Samples of empirical studies often had less than 20 participants. Participants were nightmare

sufferers drawn from the general population, militaries/veterans, minors or persons with an intellectual deficiency, and sexual assault victims. Nightmares of participants were idiopathic or posttraumatic.

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Categories of mechanisms of action. Table 1 shows, in order of importance, the six MA categories that emerged from the thematic analysis, and illustrative citation examples of these. Many citations were associated with more than one

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hypothesis. The more frequent coexistent categories for a same citation were increased sense of mastery with modification of beliefs or with emotional processing. Emotional processing could be reported,

although less frequently, with restoration of sleep functions and modification of beliefs. No MA appeared

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specific to one therapy.

The majority of all MA arguments were theoretical. A posteriori observations primarily supported

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increased sense of mastery, followed by modification of beliefs, and a few supported, in order of importance, restoration of sleep functions, emotional processing, prevention of avoidance and decreased arousal. Only five studies provided empirical data, respectively in support of increased sense of mastery (9, 19-20), modification of beliefs (21) and restoration of sleep functions (22-23).

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Discussion

The objective of this study was to identify and categorize the MAs thought to explain the efficacy of psychological nightmare treatments. A systematic review of scientific publications in the field of empirically supported nightmare treatments was performed. Publications were scrutinized to sort citations

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referring to a MA and their explanation. These citations were synthesized under six categories through a qualitative thematic analysis.

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This review allowed us to note that many authors recognise the relevance of mechanisms

underlying the efficacy of nightmare treatments. Paradoxically, MAs are not measured and if referred to, they lack crucial support. An increased sense of mastery was the most frequent hypothesis, followed by emotional processing and modification of beliefs. Less frequently cited MAs were restoration of sleep functions, decreased arousal and prevention of avoidance. These mechanisms could be interrelated, as authors often discussed more than one at a time, and the six categories could hardly be dissociated from one another. No MA was specific to any treatment approach; it thus remains unclear whether any

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therapeutic component is associated with a specific MA. This highlights the fact that dispersion of protocols is probably futile.

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Critical comments. Increased sense of mastery.

Increased sense of mastery, beyond cognition, is a feeling, a deep conviction that one is in control of one’s nightmares. It supposes that a lack of control over one’s dreams explains nightmare recurrence.

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This MA concerns one’s capacities, as opposed to the modification of beliefs MA which concerns

cognitions about the nightmare phenomenon. It has garnered the most support, through its empirical

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demonstrations and numerous observations made during efficacy studies. For example, many revised scripts made in therapy contained themes about mastery (21). In an IRT protocol, it was found that new scripts, compared to previous nightmares, had more mastery elements, more modalities in which to express mastery, and more positive elements, all changes that favour increased mastery (9). Although less

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present, some negative elements were still present in the new script, suggesting patients decided to exercise control over them. Further evidence is presented by Miller et al. (19) in a study in which military personnel with PTSD received ERRT: the authors found a negative correlation between internal locus of control regarding sleep and nightmares, and self-reported sleep latency. Finally, Harb et al. (20) showed

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that IRT allows patients to increase the perceived occurrence that they control their dreams’ content (a

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lucid dreaming construct), which was associated with decreased nightmare distress. Sense of mastery could be gained through different therapeutic components: modifying a

nightmare scenario, practicing to become lucid, imaginal exposure to the nightmare scenario or relaxation techniques, which allow the patient to feel in control over his or her emotions. Although the construct seems straightforward, a closer examination reveals confusion regarding the object over which mastery should be gained: the recurrent nightmare scenario, the process of dreaming more generally, selfconfidence, cognition, emotions, or one’s own imagery system. Plus, the “sense of mastery” construct is not included in nightmare theoretical models (10, 12, 13-14) and is not generally encountered in the field

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of clinical psychology research. Its operationalization thus remains a challenge. Perceived self-efficacy, a validated construct similar to sense of mastery, is one’s perceived capacity to manage one’s own behaviors, cognitions and motivation to exert control over external demands, and the perception that one’s

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actions will have the desired effects (24-25). Self-efficacy was shown to be a reliable concept in PTSD (26). Since nightmares can be a PTSD-related symptom, self-efficacy may be a more valid and reliable construct to designate sense of mastery: treatment for nightmares may thus work via an increase in self-

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efficacy. Emotional processing.

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Emotional processing is the process through which the fear structure, a memory network composed of conscious and unconscious information to react to dangerous stimuli, is modified (27). As for other PTSD symptoms, it is thought that nightmares are caused by the fact that neutral stimuli are considered dangerous, which can generate generalized fear reactions. In order to be modified, the fear structure must be activated while emotional and cognitive information incompatible with it is incorporated

theoretical model (13-14).

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(27). The fear structure concept seems coherent with the fear memory component of Nielsen and Levin's

Overall, authors suggest that emotional processing can be achieved through exposure to the

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phobic stimulus (i.e., habituation). Many authors have hypothesized that the nightmare content represents the fear stimulus in people suffering from recurrent nightmares. However, an issue regarding habituation

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concerns the presence or absence of exposure to nightmare content in protocols based on imagery rehearsal. Lancee et al. (28) argued that rescripting a nightmare is exposure in itself; because IRT and exposure treatments are equally effective, they proposed that exposure would be the therapeutic ingredient. An opposing perspective is that IRT limits exposure to the original nightmare content; if present, exposure would be insufficient to allow emotional processing (8). A meta-analysis and a dismantling study have shown no difference in efficacy between protocols based on rescripting that

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specifically include or exclude exposure to the original nightmare (2, 29-30), which would support the point that habituation is not a MA of IRT. An alternative hypothesis that could reconcile the perspectives about exposure in rescripting

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would be that the feared situation is the nightmare phenomenon in general, instead of the nightmare content. Indeed, distress could have been generalized to cues associated with nightmare occurences, such as sleep in general, the bed and the feeling of relaxation (10). If the nightmare phenomenon is part of the

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fear structure, a potential research avenue would be to identify 1) cues associated with it (e.g. bedtime routine, bedroom, beliefs about nightmares, threat cues in dreams, etc.); 2) the nightmare treatment

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components that are likely to induce incompatible information to these cues (e.g. relaxation, psychoeducation, visualising a new script); and 3) the moments during which the fear structure is activated in order for emotional processing to be effective (e.g. before sleep). Modification of beliefs.

Modification of beliefs is also thought to be involved in all psychological treatment categories and

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mainly implies that erroneous cognitive patterns are the cause of recurrent nightmares. Cognitive restructuring is thought to occur in two ways: the nightmare itself is conceptualized as an erroneous cognition or it is the erroneous cognitions about nightmares that must be modified. In the first instance,

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nightmares have been defined as a modifiable habit or a script that can be replaced (12, 31). However, it is difficult to conclude that nightmare scripts are "replaced" as patients often don't dream the new script

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developed in IRT (32) and as this conception cannot account for the efficacy of exposure treatments. The view of nightmares as a maladaptive cognition requires further evidence to be supported. On the other hand, maybe cognitions about the nightmare phenomenon need to be addressed. The

fact that some nightmares did not seem to have changed in content but were no longer considered distressing could attest to the change in perception (33). In a treatment study for PTSD, nightmare distress has been shown to decrease after psychoeducation is implemented, as it allowed for beliefs about

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nightmares to be modified (34). However, a contradictory result showed psychoeducation alone didn't improve frequency and severity of nightmares in IRT protocols (35). Dysfunctional beliefs related to the trauma theme found in a nightmare are thought to perpetuate

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posttraumatic nightmares. A trauma theme was defined by Davis and Wright (36) as the "unresolved cognitive-affective meaning structures and processes" (p.9). An empirical result supporting this hypothesis was offered by Harb et al. (21), who found that addressing the nightmare theme increased treatment

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response; they thus proposed that working with the nightmare theme would enable individuals to

cognitively restructure the meaning of the trauma and to understand it. Furthermore, it appears that

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modifying the nightmare script without conviction would be inefficient (37). These results highlight thematic exploration as a potential moderator variable of nightmare treatments’ efficacy more than as a MA.

There is a need to identify the most common dysfunctional beliefs about nightmares that could play a role in their persistence. This endeavor could be modeled after the construction of the self-reported

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Dysfunctional beliefs about sleep questionnaire (38), which has been shown to be a discriminant measure of cognitions (39) mediating the effect of insomnia treatment (40). Restoration of sleep functions.

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Disruption of sleep pathophysiology is thought to explain nightmares’ recurrence. Evidence suggests sleep plays an important role in learning and memory processes (41) as well as in perception,

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expression and regulation of emotions (42). Sleep loss has been associated with affected emotion experience, mood disturbances and affective psychopathology, which is thought to be caused by the effect of sleep loss on frontal brain regions associated with emotion regulation and cognitive control (43). Especially, the REM stage of sleep, in which most dreaming occurs, is thought to allow proper consolidation of salient memories (42), emotional processing (22) and fear conditioning or extinction (44). It has been proposed that altered REM sleep is associated with idiopathic nightmares; moreover, before and after a traumatic event, altered REM sleep, poor sleep and nightmares were associated with the

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development and persistence of PTSD (44). Restoration of sleep functions could thus be conceptualized as a form of emotional processing occuring during sleep. Germain and Nielsen (22) offered important empirical support for this view: they observed increased arousal and REM sleep after IRT for patients

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suffering from post-traumatic nightmares, which they interpreted as the effect of emotional processing in PTSD. It was thought that links were created between emotional and cognitive content in order to regulate emotions and consolidate memory.

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However, the specific processes by which nightmare treatments impact REM and non-REM sleep remain unknown. One hypothesis is that therapy would be efficient in restoring patients’ capacity to

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control their imagery system during the day, which would then generalize onto nocturnal imagery (45). Ellis (46) suggested that the creativity required to think of a new end to a nightmare scenario could in fact work towards the same ends as the dream itself, i.e. allowing new associations and reducing emotional charge. In this manner, going through this process while awake would help reinstate sleep functions. Nevertheless, this category of MA exposes an often encountered confusion between the role of rapid eye

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movement (REM) sleep and of dream content to explain efficacy of nightmare treatments. According to theories of dreams, the functions of dreams seem very similar to the ones of REM sleep, namely correction of emotional experience (10), fear extinction (13-14) and development of new cognitive and

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emotional associations in order to integrate memories (46-47). However, it remains unclear whether this role is attributable to REM sleep or to dreams per see. If a dream content recalled to awakening can

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produce new associations between dream phenomenon and positive emotions (which would be emotional processing MA, as occurring awaked), we do not know to what extent the content of a non remembered dream allows these new associations during sleep. Maladaptive sleep behaviors adopted to deal with nightmares (e.g. avoidance of sleep) could lead

to sleep deprivation and its consequences (distress, confusion, diminished concentration, emotional lability), which would increase the risk of having more nightmares (10). Thus, one hypothesis is that insomnia management strategies consolidate sleep and impact nightmares. However, while adding these

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treatment components to the IRT protocol increased sleep quality, it didn't lead to further improvement of nightmares (2). The restoration of sleep functions as a MA of nightmare treatment has much supporting evidence

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in the field of dream research; moreover, this MA somewhat bridges the gap between the literature on nightmare treatments and that on dreams. To further understand the function of REM sleep and dreams through therapy, nightmare treatment efficacy studies should include parameters of sleep (e.g.

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polysomnography) whenever possible. Decreased arousal.

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Many authors cite physiological arousal as an important contributor to nightmare creation. Being afraid to fall asleep has been shown to be correlated with higher nightmare frequency (48). ERRT has been found effective at reducing physiological arousal (heart rate, skin conductance and corrugator activity) of participants asked to imagine their nightmare’s content (49-50). These results were associated with improvement of various sleep parameters (e.g. sleep quality and quantity, nightmare severity) (49).

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However, the ways in which arousal is said to impact nightmares varies. Several MAs could be responsible of decreasing arousal: increased sense of mastery, modification of beliefs, emotional processing. On the other hand, some findings suggest that relaxation and breathing exercises alone could

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be sufficient to decrease nightmare frequency and intensity (51). Furthermore, decreased arousal could occur at different times: before sleep, in allowing patients to fall asleep earlier and avoid unhelpful

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cognitions causing nightmares, as well as during sleep, in decreasing the chance of a nightmare being activated (12) and allowing flexibility of the fear structure to facilitate fear extinction (14). Thus, arousal could be considered a diurn maintenance factor (e.g. anxiety anticipation) that can be addressed through decreased arousal MA, while its regulation during sleep seems to belong to restoration of sleep functions. Prevention of avoidance. For most patients, nightmares are a distressing and uncontrollable experience. Many regulate their distress with cognitive or behavioral avoidance, i.e. trying to not think about it or avoiding sleep (10).

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However, avoidance may act as a nightmare maintenance factor (3). Indeed, in healthy subjects, avoiding some thoughts before sleep was associated with dreaming about these thoughts, distress in dreams and perceived stress (52). Spoormaker (12) stipulates cognitive avoidance would reinforce the nightmare’s

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script in memory as it provides no opportunity for its fearfulness to be reconsidered. Thus, prevention of avoidance might allow for better emotional processing of the nightmare content, by allowing for activation and modification of the fear structure. Here, sense of mastery could be helpful in order to confront

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nightmares. In a case study, a patient was unable to expose himself to his nightmare content without modifying the nightmare’s script (53), which suggests an increased sense of mastery is necessary to

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prevent avoidance.

Authors refer to different coping strategies according to the treatment protocol that is studied: psychoeducation, nightmare diary, imaginal exposure to the nightmare, rescripting the nightmare, learning to become lucid, etc. Possibly, these coping strategies all have the advantage of preventing avoidance of the cues associated to nightmares. Consequently, nightmare treatments and future research should focus

Theoretical implications.

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more on the role of avoidance in the maintenance of nightmare.

This review aimed to understand how psychological nightmare treatments work; it showed that a

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single straightforward answer to this complex question does not exist. Indeed, there were numerous hypotheses and a lot of overlap between them, exemplified by the fact that many citations were coded in

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more than one category and that MA definitions are not exclusive. Different processes may work together to impact nightmares at different levels. As all maintaining factors of recurring nightmares are thought to influence one another, it is suggested that intervening on any of them could effectively help break the vicious nightmare cycle (27). We propose an illustration (see Figure 1) that summarizes how we conceptualise the six MAs and the criticisms of these that emerged in this review. Our illustration proposes that the main MA in reducing nightmare frequency and severity rely on emotional processing of the fear structure, which implies activation of the fear structure and incorporation

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of incompatible elements during both day and night. As treatment is offered during wakefulness, it would achieve these two prerequisites first while the patient is awake. Any therapeutic components of supported psychological treatments included in this review are thought to prevent avoidance, thus allowing

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activation of the fear structure. Therapeutic components are then thought to increase sense of mastery, modify maladaptive beliefs and decrease arousal, all of which represent incompatible information with the fear structure at different levels (emotional, cognitive and physiological, respectively). Despite the fact

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that sense of mastery is the most frequently discussed MA in the literature, we did not considered it as the overarching MA, mainly because of the previously discussed confusion regarding its operationalization.

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We also found emotional processing to be a more comprehensive construct.

In addition, all- MAs are assumed to influence each other. For example, modification of beliefs may be necessary to allow patients to increase their sense of mastery, which would in turn decrease arousal before sleep. This emotional process, carried out when awake, would impact sleep functions: the modified fear structure, once activated in a dream, would be more amenable to further emotional

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processing. REM sleep would now be able to integrate and regulate emotions and memories (incorporation of incompatible elements) and thus, sleep interruptions would be decreased (prevention of avoidance while asleep). This restoration of sleep functions would also have an impact on sleep quality

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and quantity, which would in turn further restore sleep functions and reinforce the patient’s new beliefs about his or her capacity to control nightmares. The MA of emotional processing would in this sense be a

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bridge between processes occurring during the waking and the sleeping state. This model attempt proposes that psychological nightmare treatments are effective in intervening

on fear extinction proposed in Nielsen and Levin's model (13-14) and in addressing maintenance factors of recurring nightmares of Spoormaker (12) and Davis' (10) models.

Clinical implications. For clinicians, this first theoretical conceptualization towards understanding nightmare treatments suggests that therapeutic techniques per se, let alone therapy labels, are probably less important to

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improving treatment protocols than ensuring proper MAs have been triggered for each patient. Thus, clinicians should orient their work towards promoting emotional processing of the nightmare’s fear structure. To this end, the proposed illustration has gathered different treatment propositions (IRT, ERRT,

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lucid dreaming treatments, exposure) in a set of tools that are thought to be efficacious for activating different MAs, all of which contribute to emotional processing. Emotional processing could be effective when incompatible information is incorporated into the activated fear structure related with the nightmare

identifying cues associated with fear of nightmares.

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Study limitations and strengths.

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phenomenon. Consequently, clinicians could adapt their treatment to the particularities of the patient, in

The present results should be considered in light of certain limitations. There are many more studies of therapies based on rescripting compared to other protocols published; it is thus possible that some research groups had more opportunities to express their ideas of how their treatment works. Similarly, some unsupported or yet-to-be-supported observations and hypotheses of authors in the field of

model attempt.

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nightmare treatments may not have been published and, for this reason, were not taken into account in this

The proposed illustration could be overly simplistic and may gain from being refined: the ways in

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which MAs are interrelated remain to be tested. Results show that nightmare frequency and intensity appear to be impacted differently (10, 22, 34-35); it is possible that MAs could differently influence

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measured outcomes. Additionally, most of the hypotheses on which the model is based are theoretical and have little empirical support; the model must thus be interpreted with caution while awaiting supporting data.

Despite these limitations, this study is the first to systematically review explanations of the

mechanisms underlying efficacy of psychological nightmare treatments offered by experts in the domain and to propose an integrative conceptualization of how psychological treatments for nightmares work. The method used is innovative in that it combines a systematic review with a qualitative analysis. This allowed

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for scattered information, often drawn from observations and reasoning found in the discussion sections of articles, to be merged in order to identify relevant information. This study allowed for recognition of different kind of arguments for each hypothesis. It allows for identification of 6 main MAs and offered

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research avenues to lend empirical support to these.

Practice points •

Treatments for nightmares have yielded support for their effectiveness, but no consensus exists to

•

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explain how they work.

According to the literature, possible mechanisms of action explaining nightmare treatments'

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efficacy could be an increased sense of mastery, emotional processing, modification of beliefs, restoration of sleep functions, decreased arousal, and prevention of avoidance. •

We propose that the main mechanism of action of nightmare treatments is emotional processing, which leads to the modification of the fear structure associated with nightmares. Restoration of sleep functions would allow for emotional processing while asleep, possibly during REM sleep.

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Increased sense of mastery, modification of beliefs, decreased arousal and prevention of avoidance may all modify the fear structure associated with nightmares; clinicians should target

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these mechanisms to allow emotional processing.

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•

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Research Agenda •

Dismantling studies of nightmare treatment components could allow the demonstration of the

outcome variables. •

To demonstrate the effect of a mechanism of action, research protocols should include several data collection points during treatment.

Measuring more than one mechanism of action, i.e., increased sense of mastery, emotional

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•

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specific contributions of each therapeutic component on the different mechanisms of action and

processing, modification of beliefs, restoration of sleep functions, decreased arousal, and

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prevention of avoidance, would allow documenting of their interrelation.

Acknowledgements

The first author was awarded a master's scholarship from the Canadian Institutes for Health Research. The

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authors have no conflict of interest to disclose.

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References 1.

Augedal AW, Hansen KS, Kronhaug CR, Harvey AG, Pallesen S. Randomized controlled trials of

psychological and pharmacological treatments for nightmares: A meta-analysis. Sleep Med Rev 2013;

2.

RI PT

17(2): 143-52. Casement MD, Swanson LM. A meta-analysis of imagery rehearsal for post-trauma nightmares:

Effects on nightmare frequency, sleep quality, and posttraumatic stress. Clin Psychol Rev 2012; 32(6):

3.

SC

566-74.

Hansen K, Höfling V, Kröner-Borowik T, Stangier U, Steil R. Efficacy of psychological

M AN U

interventions aiming to reduce chronic nightmares: A meta-analysis. Clin Psychol Rev 2013; 33(1): 14655. 4.

Ho FY-Y, Chan CS, Tang KN-S. Cognitive-behavioral therapy for sleep disturbances in treating

posttraumatic stress disorder symptoms: A meta-analysis of randomized controlled trials. Clin Psychol Rev 2016; 43: 90-102.

Aurora RN, Zak RS, Auerbach SH, Casey KR, Chowdhuri S, Karippot A, et al. Best practice

TE D

5.

guide for the treatment of nightmare disorder in adults. J clin sleep med 2010; 6(4): 389-401. *6.

Harb GC, Phelps AJ, Forbes D, Ross RJ, Gehrman PR, Cook JM. A critical review of the

EP

evidence base of imagery rehearsal for posttraumatic nightmares: Pointing the way for future research. J Trauma Stress 2013; 26(5): 570-9.

Kazdin AE. Mediators and mechanisms of change in psychotherapy research. Annu Rev Clinic

AC C

7.

Psychol 2007; 3: 1-27. 8.

Nappi CM, Drummond SPA, Hall JMH. Treating nightmares and insomnia in posttraumatic stress

disorder: A review of current evidence. Neuropharmacol 2012; 62(2): 576-85. *9.

Germain A, Krakow B, Faucher B, Zadra A, Nielsen T, Hollifield M, et al. Increased Mastery

Elements Associated With Imagery Rehearsal Treatment for Nightmares in Sexual Assault Survivors With PTSD. Dreaming 2004; 14(4): 195-206.

ACCEPTED MANUSCRIPT

*10.

Davis JL. Treating post-trauma nightmares: A cognitive behavioral approach. New York, NY, US:

Springer Publishing Co 2009. xviii, 290 p. 11.

Krakow B, Hollifield M, Schrader R, Koss M, Tandberg D, Lauriello J, et al. A controlled study

RI PT

of imagery rehearsal for chronic nightmares in sexual assault survivors with PTSD: A preliminary report. J Trauma Stress 2000; 13(4): 589-609.

Spoormaker VI. A cognitive model of recurrent nightmares. Int J Dream Res 2008; 1(1): 15-22

*13.

Nielsen T, Levin R. Nightmares: A new neurocognitive model. Sleep Med Rev 2007; 11(4): 295-

SC

*12.

310.

Levin R, Nielsen TA. Disturbed dreaming, posttraumatic stress disorder, and affect distress: A

M AN U

14.

review and neurocognitive model. Psychol Bull 2007; 133(3): 482-528. 15.

Atkins S, Lewin S, Smith H, Engel M, Fretheim A, Volmink J. Conducting a meta-ethnography of

qualitative literature: Lessons learnt. BMC Med Res Methodol 2008; 8(1): 21. 16.

Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and

17.

TE D

meta-analyses: the PRISMA statement. PLoS Med 2009; 6(7).

Côte L, Turgeon J. Comment lire de façon critique les articles de recherche qualitative en

médecine. Pédagogie Médicale 2002; 3(2): 81-90.

Eichelman B. Hypnotic change in combat dreams of two veterans with posttraumatic stress

EP

18.

disorder. Am J Psychiatry 1985; 142(1): 112-4. Miller KE, Davis JL, Balliett NE. Taking Control: Examining the Influence of Locus of Control

AC C

*19.

on the Treatment of Nightmares and Sleep Impairment in Veterans. Mil Behav Health 2014; 2(4): 337-42. *20.

Harb GC, Brownlow JA, Ross RJ. Posttraumatic nightmares and imagery rehearsal: The possible

role of lucid dreaming. Dreaming 2016; 26(3): 238-49. *21.

Harb GC, Thompson R, Ross RJ, Cook JM. Combat‐related PTSD nightmares and imagery

rehearsal: Nightmare characteristics and relation to treatment outcome. J Trauma Stress 2012; 25(5): 5118.

ACCEPTED MANUSCRIPT

*22.

Germain A, Nielsen T. Impact of Imagery Rehearsal Treatment on Distressing Dreams,

Psychological Distress, and Sleep Parameters in Nightmare Patients. Behav Sleep Med 2003; 1(3): 140-54. 23.

Germain A. Sleep pathophysiology and cognitive-behavioral treatment of posttraumatic and

Bandura A. Self-efficacy: Toward a unifying theory of behavioral change. Psychol Rev 1977;

84(2): 191-215. 25.

Maddux JE. Self-efficacy, adaptation, and adjustment: Theory, research, and application. Maddux

JE, editor. New York, NY, US: Plenum Press 1995. xvii, 395 p.

Benight CC, Bandura A. Social cognitive theory of posttraumatic recovery: The role of perceived

M AN U

26.

SC

24.

RI PT

idiopathic nightmares. US: PQIL 2002.

self-efficacy. Behav Res Ther 2004; 42(10): 1129-48. *27.

Foa EB, Kozak MJ. Emotional processing of fear: Exposure to corrective information. Psychol

Bull 1986; 99(1): 20-35. 28.

Lancee J, van den Bout J, Spoormaker VI. Expanding self-help Imagery Rehearsal Therapy for

TE D

nightmares with sleep hygiene and lucid dreaming: A waiting-list controlled trial. Int J Dream Res 2010; 3(2): 111-20. 29.

Pruiksma KE, Cranston CC, Rhudy JL, Micol RL, Davis JL. Randomized Controlled Trial to

EP

Dismantle Exposure, Relaxation, and Rescripting Therapy (ERRT) for Trauma-Related Nightmares. Psychol Trauma 2016.

Cranston CC. A randomized controlled trial to dismantle components of exposure, relaxation, and

AC C

30.

rescripting therapy for chronic nightmares and sleep disturbances in trauma-exposed persons. US: PQIL 2016. 31.

Nadorff MR, Lambdin KK, Germain A. Pharmacological and non-pharmacological treatments for

nightmare disorder. Int Rev Psychiatry 2014; 26(2): 225-36. 32.

St-Onge M, Mercier P, De Koninck J. Imagery rehearsal therapy for frequent nightmares in

children. Behav Sleep Med 2009; 7(2): 81-98.

ACCEPTED MANUSCRIPT

33.

Zadra AL, Pihl RO. Lucid dreaming as a treatment for recurrent nightmares. Psychother

Psychosom 1997; 66(1): 50-5. 34.

Krakow B. Nightmare therapy: Emerging concepts from sleep medicine. In: Glucksman MKM,

Francis Group 2015. 149-60.

Simard V, Nielsen T. Adaptation of imagery rehearsal therapy for nightmares in children: A brief

report. Psychother: Theor, Res, Pract, Train 2009; 46(4): 492-7. 36.

Davis JL, Wright DC. Exposure, relaxation, and rescripting treatment for trauma-related

M AN U

nightmares. J Trauma Dissociation 2006; 7(1): 5-18. 37.

SC

35.

RI PT

editor. Dream research: Contributions to clinical practice. New York, NY, US: Routledge/Taylor &

Kellner R, Singh G, Irigoyen-Rascon F. Rehearsal in the treatment of recurring nightmares in

posttraumatic stress disorders and panic disorder: Case histories. Ann Clin Psychiatry 1991; 3(1): 67-71. 38.

Morin CM. Insomnia: Psychological assessment and management. New York, NY, US: Guilford

Press 1993. xvii, 238 p.

Espie CA, Inglis SJ, Harvey L, Tessier S. Insomniacs' attributions: Psychometric properties of the

TE D

39.

Dysfunctional Beliefs and Attitudes about Sleep Scale and the Sleep Disturbance Questionnaire. J Psychosom Res 2000; 48(2): 141-8.

Eidelman P, Talbot L, Ivers H, Bélanger L, Morin CM, Harvey AG. Change in dysfunctional

EP

40.

beliefs about sleep in behavior therapy, cognitive therapy, and cognitive-behavioral therapy for insomnia.

41.

AC C

Behav Ther 2016; 47(1): 102-15.

Stickgold R, Walker MP. Sleep-dependent memory consolidation and reconsolidation. Sleep Med

2007; 8(4): 331-43. 42.

Van der Helm E, Walker MP. Sleep and affective brain regulation. Soc Personal Psychol

Compass 2012; 6(11): 773-91. 43.

Watling, J., Pawlik, B., Scott, K., Booth, S., & Short, M. A.. Sleep Loss and Affective

Functioning: More Than Just Mood. Behav Sleep Med 2017, 15(5), 394-409.

ACCEPTED MANUSCRIPT

44.

Germain A. Sleep disturbances as the hallmark of PTSD: Where are we now? Am J Psychiatry

2013; 170(4): 372-82. 45.

Krakow B. Nightmare complaints in treatment-seeking patients in clinical sleep medicine settings:

Ellis LA. Qualitative changes in recurrent PTSD nightmares after focusing-oriented dreamwork.

Dreaming 2016; 26(3): 185-201. 47.

Hartmann E. Nightmare after trauma as paradigm for all dreams: A new approach to the nature

and functions of dreaming. Psychiatry. 1998; 61(3): 223-38.

Neylan TC, Marmar CR, Metzler TJ, Weiss DS, Zatzick DF, Delucchi KL, et al. Sleep

M AN U

48.

SC

46.

RI PT

diagnostic and treatment implications. Sleep 2006; 29(10): 1313-9.

disturbances in the Vietnam generation: Findings from a nationally representative sample of male Vietnam veterans. Am J Psychiatry 1998; 155(7): 929-33. 49.

Davis JL, Rhudy JL, Pruiksma KE, Byrd P, Williams AE, McCabe KM, et al. Physiological

predictors of response to exposure, relaxation, and rescripting therapy for chronic nightmares in a

50.

TE D

randomized clinical trial. J clin sleep med 2011; 7(6): 622-31.

Rhudy JL, Davis JL, Williams AE, McCabe KM, Bartley EJ, Byrd PM, et al. Cognitive-

behavioral treatment for chronic nightmares in trauma-exposed persons: assessing physiological reactions

51.

EP

to nightmare-related fear. J Clin Psychol 2010; 66(4): 365-82. Miller WR, DiPilato M. Treatment of nightmares via relaxation and desensitization: A controlled

52.

AC C

evaluation. J Consult Clin Psychol 1983; 51(6): 870-7. Kröner‐Borowik T, Gosch S, Hansen K, Borowik B, Schredl M, Steil R. The effects of

suppressing intrusive thoughts on dream content, dream distress and psychological parameters. J Sleep Res 2013; 22(5): 600-4. 53.

Bishay N. Therapeutic manipulation of nightmares and the management of neuroses. Br J

Psychiatry 1985; 147: 67-70. 54.

Spoormaker VI, Bout Jvd, Meijer EJG. Lucid Dreaming Treatment for Nightmares: A Series of

Cases. Dreaming 2003; 13(3): 181-6.

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55.

Davis JL, Byrd P, Rhudy JL, Wright DC. Characteristics of chronic nightmares in a trauma-

exposed treatment-seeking sample. Dreaming 2007;17(4):187-98. 56.

Pruiksma KME. A randomized controlled trial of exposure, relaxation, and rescripting therapy and

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relaxation training for chronic nightmares in trauma-exposed persons: Findings at one week posttreatment.

AC C

EP

TE D

M AN U

SC

US: PQIL 2012.

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Figure 1. Proposed illustration of the different variables involved in nightmare treatments. This conceptualization includes the six mechanisms of action (MA) hypotheses found in the literature (in bold characters). The main MA is emotional processing, which is the modification of the fear structure, an

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association of cognitive, emotional and behavioral information about nightmares. Increased sense of mastery, modification of beliefs, decreased arousal and prevention of avoidance act as diurnal MAs

allowing emotional processing. This process done during the day would allow the restoration of sleep

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functions, which consists in regulation of arousal, integration of incompatible information in dreams and sleep continuity. The same cognitive, emotional and behavioral information of the fear structure is

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activated, but its modification is processed in multiple ways, according to different diurnal or nocturnal

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MAs.

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Table 1 Mechanisms of actions, theoretical implications and examples of supporting citations Description

action

Presumed theoretical

Treatments

cause of nightmares

associated

Examples of citations associated to

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Mechanism of

Patients develop the conviction, the

Repetitive nightmares are

- Therapies based on

This could be caused by a sense of mastery participants

mastery

core belief and feeling that they

caused by a lack of

rescripting

experienced when realizing that nightmares can be

have control over their dreams,

perceived control

- Lucid dreaming

overcome. To know that one can control the nightmare is

- Exposure

possibly equally as important as actually controlling it

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Increased sense of

recurrent nightmares or mental

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imagery

(p.185) (54).

The fear structure, containing

Repetitive nightmares are

- Therapies based on

The exposure component in ERRT may work much as it

processing

information on feared stimuli

caused by a fear structure

rescripting

does in PTSD treatments, in that participants learn to

associated with nightmare

where stimuli associated

- Exposure

face their fear in a safe environment; this exposure

phenomenon, is modified

with nightmares and fear

beliefs

nightmare occurrence are modified

correct problematic aspects of the fear structure (p.130)

dangerous

(55).

Repetitive nightmares are

- Therapies based on

We believe that nightmares may be a catastrophized

caused by maladaptive

rescripting

response conditioned by abnormal cognitive processing

beliefs about nightmares or

- Lucid dreaming

and hypervigilance during sleep. To accept such a

unresolved themes that are

- Exposure

paradigm, the participant usually must consider the

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Maladaptive beliefs promoting

provides a corrective learning experience and may

reactions are interpreted as

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Modification of

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Emotional

depicted in nightmares

distinct possibility that nightmares are in fact eminently controllable by cognitive restructuring, and that they do not necessarily represent deeper psychic conflicts about

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their trauma (p.601) (11). REM sleep and dreams, thought to

Nightmares are caused by

- Therapies based on

In the case of posttraumatic-nightmares patients, we

sleep functions

have a role in integration of

disrupted functions of

rescripting

propose that the observed changes reflect an activation

information and emotions, is

dreams, REM and non-

- Exposure

restored, while all stages of sleep

REM sleep

of emotional processing in REM sleep instigated by treatment. […] Our observed increases in both micro-

are no more interrupted

Repetitive nightmares are

before and/or during sleep

caused by an arousal state

- Therapies based on

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Physiological arousal is reduced

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arousals and REM density may reflect increases in

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Decreased arousal

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Restoration of

emotional processing during sleep (p.74) (23). The relaxation component of the treatment focuses on

rescripting

decreasing physiological anxiety, tension, and cognitive

- Exposure

activity prior to sleep. Progressive muscle relaxation may help to reduce anticipatory anxiety regarding going to sleep by relaxing the body and mind, perhaps clearing the mind of thoughts that may increase the chance of having a nightmare (p.204) (10).

Patients get new tools to cope with

Repetitive nightmares are

- Therapies based on

By avoiding confrontation with the nightmare, anxiety is

avoidance

nightmares and no longer rely on

the result of behavioral and

rescripting

maintained and may increase over time. [...] Confronting

cognitive avoidance

- Lucid dreaming

the nightmare in treatment is thought to decrease

- Exposure

avoidance, thereby alleviating distress (p.101) (56).

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avoidance

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Prevention of

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Emotional processing

Outcomes

Asleep

Awake

(Restoration of sleep functions)

Emotional

REM sleep and dreams

- Modification of beliefs - Increased sense of mastery

Decreased arousal

Integration, consolidation and regulation of emotions and memories

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Cognitive

Behavioral

Prevention of avoidance to nightmare-related stimuli

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- Rescripting nightmares - Imaginal exposure - Practicing lucid dreaming - Psychoeducation/ cognitive restructuring - Relaxation, breathing - Exploration of nightmare theme - Practice of mental imagery - Nightmare diary keeping - Sleep hygiene education, sleep restriction and stimulus control

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(modification of the fear structure)

Therapeutic strategies

Non-REM sleep Improvement of sleep continuity

- Decreased nightmare frequency - Decreased nightmare distress - Improved sleep quality - Decreased daytime consequences of poor sleep