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Introduction Fear of sleep is proposed to contribute to pathogenic processes underlying trauma-related sleep disturbances. The Fear of Sleep Inventory (FOSI) and its short form (FOSI-SF) appear to be suitable instruments to investigate this construct, yet only English versions are currently available. Objective To facilitate the cross-cultural investigation of fear of sleep, this study aimed at providing a German version of the FOSI-SF, and investigating its psychometric properties as well as its associations with clinically significant PTSD and insomnia. Method The German version of the FOSI-SF was generated following the principle of forward-backward translation and administered to a large online sample from the German general population (n = 754), next to measures of PTSD symptom severity, insomnia severity, and sleep quality. Results The German FOSI-SF has good internal consistency (Cronbach's α = .87). The factorial structure remains inconclusive because exploratory and confirmatory factor analysis detected Heywood cases. Convergent validity was confirmed by moderate to high correlations with PTSD symptoms, insomnia severity, and sleep quality (rs = .30 to .47). Participants reporting clinically relevant PTSD symptoms expressed significantly higher fear of sleep than participants without PTSD (ω2 = .053). Furthermore, participants with insomnia reported significantly increased levels of fear of sleep relative to participants without insomnia (ω2 = .011). Conclusion These results indicate that the German FOSI-SF is sensitive to the theoretically-related disorders of PTSD and insomnia. Overall, the German FOSI-SF offers an economic and practicable brief measure of sleep fears that can enhance further insights into trauma-related sleep disturbances.

Imagery rescripting (IR) and imaginal exposure (IE) are two efficacious treatments for nightmare disorder, but their discrete underlying mechanism(s) remain largely unknown. We therefore examined mediators of the treatment effects of IR and IE in a randomized wait-list controlled trial (N = 104). Therapeutic outcomes were assessed at pre- and post-assessment, and mediator assessment took place in between treatment sessions to establish a temporal relationship between mediators and nightmare symptoms (i.e., frequency and distress). In line with the hypothesis, enhanced mastery (or self-efficacy) of the nightmare content mediated the therapeutic efficacy of IR. Furthermore, the treatment effects of IE were mediated by increased tolerability of the negative emotions elicited by nightmares. Even though IR and IE for nightmares seem to produce similar therapeutic effects, the results of this study suggest that IR and IE tap into different underlying processes.

The currently best-supported psychological treatment for nightmares is imagery rehearsal therapy. The problem, however, is that not enough trained practitioners are available to offer this treatment. A possible solution is to conduct imagery rehearsal therapy in a guided self-help format. In the current study, 70 participants with nightmares according to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders were randomized to either telephone-guided imagery rehearsal therapy (n = 36) or a wait-list condition (n = 34). Participants in the imagery rehearsal therapy condition received three sessions over the course of 5 weeks. Every treatment session was followed by telephone support delivered by postgraduate students. Participants who received imagery rehearsal therapy showed larger improvements on nightmare frequency (d = 1.03; p d = 0.75; p d = 1.12; p

Background Trauma-related sleep disturbances constitute critical symptoms of posttraumatic stress disorder (PTSD), but sleep symptoms often reside even after successful trauma-focused psychotherapy. Therefore, currently unattended factors – like fear of sleep (FoS) – might play a crucial role in the development and maintenance of residual sleep disturbances. However, it is unclear whether trauma-exposed individuals exhibit different symptomatic profiles of sleep disturbances that could inform individualized therapeutic approaches and eventually enhance treatment efficacy. Method In a large online study, a two-step cluster analysis and a hierarchical cluster analysis using Ward’s method were performed to explore subgroups among trauma-exposed individuals (N = 471) in terms of FoS, different aspects of trauma-related sleep disturbances (e.g., insomnia symptoms, nightmares, arousal), and PTSD symptoms. These variables were compared between resulting clusters using ANOVAs and Scheffé’s post-hoc tests. Results The hierarchical cluster analysis supported 3- and 4-cluster solutions. The 3-cluster solution consisted of one “healthy” (n = 199), one “subclinical” (n = 223), and one “clinical” (n = 49) cluster, with overall low, medium, and high symptomatology on all used variables. In the 4-cluster solution, the clinical cluster was further divided into two subgroups (n = 38, n = 11), where one cluster was specifically characterized by elevated somatic pre-sleep arousal and high levels of FoS. Conclusions A subgroup of trauma-exposed individuals with PTSD and sleep disturbances suffers from increased pre-sleep arousal and FoS, which has been suggested as one possible explanation for residual sleep disturbances. In these patients, FoS might be a relevant treatment target.

Nightmares can be effectively treated with cognitive-behavioral therapies. Though it remains elusive which therapeutic elements are responsible for the beneficial effects on nightmare symptoms, imagery rescripting (IR) and imaginal exposure (IE) are commonly identified as active treatment components of nightmare therapies. With this randomized controlled trial, we compared IR and IE as individual treatments to a wait-list (WL) condition to determine whether these particular therapeutic elements ameliorate nightmare symptoms. For this purpose, 104 patients with a primary DSM-5 diagnosis of nightmare disorder were randomly assigned to three weekly individual sessions of either IR or IE, or WL. Results showed that compared to WL, both interventions effectively reduced nightmare frequency (ΔdIR-WL = 0.74; ΔdIE-WL = 0.70) and distress (ΔdIR-WL = 0.98; ΔdIE-WL = 1.35) in a sample that predominantly consisted of idiopathic nightmare sufferers. The effects of IR and IE were comparable to those observed for other psychological nightmare treatments. Initial effects at post-treatment were sustained at 3- and 6-months follow-up, indicating that IR and IE both seem to be efficacious treatment components of nightmare therapies. Additional research is needed to directly compare IR and IE among both idiographic and posttraumatic nightmare sufferers with respect to treatment expectancy, acceptability, and effectiveness.

Neuroimaging research on emotional memory has greatly advanced our understanding of the pathogenesis of anxiety disorders. While the behavioral expression of fear at the time of encoding does not predict whether an aversive experience will evolve into long-term fear memory, the application of multi-voxel pattern analysis (MVPA) for the analysis of BOLD-MRI data has recently provided a unique marker for memory formation. Here, we aimed to further investigate the utility of this marker by modulating the strength of fear memory with an α2-adrenoceptor antagonist (yohimbine HCl). Fifty-two healthy participants were randomly assigned to two conditions - either receiving 20 mg yohimbine or a placebo pill (double-blind) - prior to differential fear conditioning and MRI-scanning. We examined the strength of fear associations during acquisition and retention of fear (48 h later) by assessing the similarity of BOLD-MRI patterns and pupil dilation responses. Additionally, participants returned for a follow-up test outside the scanner (2-4 weeks), during which we assessed fear-potentiated startle responses. Replicating our previous findings, neural pattern similarity reflected the development of fear associations over time, and unlike average activation or pupil dilation, predicted the later expression of fear memory (pupil dilation 48 h later). While no effect of yohimbine was observed on markers of autonomic arousal, including salivary α-amylase (sAA), we obtained indirect evidence for the noradrenergic enhancement of fear memory consolidation: sAA levels showed a strong increase prior to fMRI scanning, irrespective of whether participants had received yohimbine, and this increase correlated with the subsequent expression of fear (48 h later). Remarkably, this noradrenergic enhancement of fear was associated with changes in neural response patterns at the time of learning. These findings provide further evidence that representational similarity analysis is a sensitive tool for studying (enhanced) memory formation.

Introduction: About 2-5% of the general population is suffering from nightmare disorder. Nightmares are associated with several negative consequences but can be effectively treated with cognitive-behavioral therapies. Imagery rescripting (IR) and imaginal exposure (IE) are commonly identified as active treatment ingredients of psychological nightmare treatments. However, it remains unclear which specific therapeutic elements are responsible for the beneficial effects on nightmare symptoms. With this randomized controlled trial, we aimed to investigate the isolated therapeutic efficacy of IR and IE for nightmares.Materials and methods: In this trial we randomized 104 patients with a primary DSM-5 diagnosis of nightmare disorder into an IR, IE, or wait-list control group. In the intervention conditions all participants received three weekly 60 minutes individual treatment sessions. The treatment conditions only consisted of IR or IE and did not comprise of treatment elements such as extensive psycho-education, relaxation and safe-place exercises, or nightmare journals.Results: Post-test results showed that compared to WL, both interventions effectively reduced nightmare frequency and distress, as well as other associated symptoms such as the number of nights with nightmares, insomnia complaints, and dysfunctional nightmare beliefs. These results were sustained at three- and six-month follow-up.Conclusions: Given that the observed effects of IR and IE were comparable to those observed in meta-analyses for other psychological nightmare treatments, we conclude that IR and IE both seem to be active treatment components in nightmare therapies. Future research is needed to examine the potential superiority or equivalence of IR and IE in the treatment of nightmares. In a similar vein, future studies should investigate the potential beneficial effects of combining IR and IE.

Background Recurrent nightmares can effectively be treated with cognitive-behavioral techniques such as imagery rehearsal therapy, which involves imagery rescripting (IR) of nightmares, and imaginal exposure (IE) therapy. However, the underlying mechanisms of these treatments remain largely unknown. To investigate this, we identified a number of variables that might mediate the therapeutic effect of rescripting-based and/or exposure-based therapies. Also, to control for the possible confounding influence of (other) treatment components, we designed two stripped-down treatment protocols, which primarily consist of either (1) rescripting of, or (2) exposure to, the nightmare content. In a randomized controlled trial, we aim to investigate the therapeutic efficacy of these stripped-down IR and IE treatments, and explore their working mechanisms. Method Three weekly sessions of either IR or IE will be compared to a waiting-list control group. Ninety participants suffering from nightmare disorder will be included and randomly allocated to one of the three groups. The primary clinical outcome measures are nightmare frequency and distress caused by nightmares. Secondary clinical outcome measures include sleep complaints, dysfunctional beliefs about nightmares, and posttraumatic stress symptom severity. Outcomes will be assessed weekly from week 1 (pre-assessment) to week 5 (post-assessment). Online follow-up assessments will take place at 3 and 6 months after post-assessment. In order to investigate temporal relationships between mediators and outcome, we will measure the proposed mediators of the treatment effect 1 day after each outcome assessment (but not after the follow-ups). Mediators include nightmare distress and valence, mastery of the nightmare content, predictability, controllability, and tolerability of emotions elicited by nightmares, as well as sleep quality. Discussion The proposed trial allows us to investigate the efficacy of IR and IE as intervention techniques for the treatment of nightmares, and to explore mediators of their respective therapeutic effects. The results may advance our understanding of nightmare therapies by identifying possible mechanisms of psychological treatments for chronic nightmares. Moreover, the results of the proposed study might provide useful knowledge about the working mechanism of rescripting-based and exposure-based treatments in general. Trial registration Netherlands Trial Register (NTR4951), registered on 14 December 2014. Electronic supplementary material The online version of this article (doi:10.1186/s13063-016-1570-3) contains supplementary material, which is available to authorized users.

This consensus paper provides an overview of the state of the art in research on the aetiology and treatment of nightmare disorder and outlines further perspectives on these issues. It presents a definition of nightmares and nightmare disorder followed by epidemiological findings, and then explains existing models of nightmare aetiology in traumatized and non‐traumatized individuals. Chronic nightmares develop through the interaction of elevated hyperarousal and impaired fear extinction. This interplay is assumed to be facilitated by trait affect distress elicited by traumatic experiences, early childhood adversity and trait susceptibility, as well as by elevated thought suppression and potentially sleep‐disordered breathing. Accordingly, different treatment options for nightmares focus on their meaning, on the chronic repetition of the nightmare or on maladaptive beliefs. Clinically, knowledge of healthcare providers about nightmare disorder and the delivery of evidence‐based interventions in the healthcare system is discussed. Based on these findings, we highlight some future perspectives and potential further developments of nightmare treatments and research into nightmare aetiology.