A novel Differential Susceptibility framework for the study of nightmares: Evidence for trait sensory processing sensitivity

The relationships between insomnia, nightmares, and dreams: A systematic review

Insomnia and nightmares are both prevalent and debilitating sleep difficulties. The present systematic review aims to document the relationships between insomnia and nightmares in individuals without a concomitant psychopathology. The relationships between insomnia and dreams are also addressed. PsycINFO and Medline were searched for papers published in English or French from 1970 to March 2023. Sixty-seven articles were included for review. Most results support positive relationships between insomnia variables and nightmare variables in individuals with insomnia, individuals with nightmares, the general population, students, children and older adults, and military personnel and veterans. These positive relationships were also apparent in the context of the COVID-19 pandemic. Some psychological interventions, such as Imagery Rehearsal Therapy, might be effective in alleviating both nightmares and insomnia symptoms. Regarding the relationships between insomnia and dreams, compared with controls, the dreams of individuals with insomnia are characterized by more negative contents and affects. The results show that insomnia and nightmares are connected and may be mutually aggravating. A model is proposed to explain how insomnia might increase the likelihood of experiencing nightmares, and how nightmares can in turn lead to sleep loss and nonrestorative sleep.

Traits linked to sensory processing sensitivity mediate the relationship between externally oriented thinking and fantasizing

Introduction

Alexithymia is characterized by difficulties identifying and describing feelings but expression of externally oriented thinking (EOT) and difficulty fantasizing is more variable. In two studies, we investigated whether links between EOT and fantasizing are mediated by sensory processing sensitivity (SPS).

Methods

University students completed measures of alexithymia, SPS, and fantasizing.

Results

In Study 1 (N = 700) we identified two clusters of SPS traits: a positive facet (sensitivity to subtle stimuli) and a negative facet (sensitivity to uncomfortable stimuli). In the 499 participants who completed the fantasy measure, low EOT scores predicted stronger SPS positive and negative traits, which predicted a stronger tendency to mentally project oneself into the lives of characters in books, movies, and plays. In Study 2 (N = 600), the link between EOT and this same fantasizing tendency was again mediated by features of SPS-in this case fantasy proneness and emotional reactivity.

Discussion

We suggest that, whereas individuals who score high on EOT have an impoverished fantasy life, those who score relatively low on EOT and turn their attention inward are able to maintain stronger representations of imagined events in working memory (enhancing the likelihood that they will be recalled) and react more strongly to these events (enhancing their salience). Stronger expression of these features of SPS, in turn, increases the likelihood that one will develop a cognitive style that involves the application of imagery-based strategies to support deep processing of the thoughts and feelings of characters depicted in narratives.

Longitudinal Study of Early Adversity and Disturbing Dream Frequency: Moderating Role of Early Negative Emotionality

Although disturbing dreams are prevalent in youth and are associated with psychopathology, little is known about their developmental course and risk factors. We aimed to examine the association between early social environment and subsequent disturbing dream frequency across adolescence as moderated by early negative emotionality. Measures of children's early social environment and negative emotionality were collected from the mothers of 410 children (5-42 months old) and measures of disturbing dream frequency directly from the children (13-18 years old). Preliminary steps identified subgroups of families with distinct profiles of social environment using latent variable mixture modeling, and captured changes in disturbing dream frequency using latent growth modeling. Regression and moderation analyses were conducted to test the study objectives. Results showed that the diverse family patterns were best captured by two profiles reflecting adverse and positive social environments and that overall disturbing dream frequency decreased during adolescence. Moderation analyses showed that when early negative emotionality was higher, DD frequency was not only more elevated in an adverse environment, but lower in a positive environment. These results indicate that the development of disturbing dreams is most strongly associated with a combination of individual and environment factors. Our study adds to the literature by refining our conception of individual traits and disturbing dream development and has implications for the prevention of bad dreams, nightmares, and associated psychopathologies.

Nightmare distress, insomnia and resilience of nursing staff in the post-pandemic era

Introduction

The pandemic has led to notable psychological challenges among healthcare professionals, including nurses.

Objective

Our aims of this study were to assess insomnia and nightmare distress levels in nurses and investigate their association with mental resilience.

Methods

Nurses participated in an online survey, which included the Nightmare Distress Questionnaire (NDQ), Brief Resilience Scale (BRS) and Athens Insomnia Scale (AIS). Demographic information, such as age, professional experience and gender, was also collected.

Results

The study included 355 female and 78 male nurses. Findings revealed that 61.4% had abnormal AIS scores, 7% had abnormal NDQ scores and 25.4% had low BRS scores. Female nurses had higher AIS and NDQ scores but lower BRS scores compared to males. BRS demonstrated negative correlations with both AIS and NDQ. Multiple regression analysis indicated that NDQ accounted for 24% of the AIS variance, with an additional 6.5% explained by the BRS. BRS acted as a mediator, attenuating the impact of nightmares on insomnia, with gender moderating this relationship.

Conclusions

Nursing staff experienced heightened sleep disturbances during the pandemic, with nightmares and insomnia being prevalent. Nightmares significantly contributed to insomnia, but mental resilience played a vital role in mitigating this effect. Strategies are warranted to address the pandemic's psychological impact on nursing professionals.

Nightmares, interoceptive sensibility and nociception: An exploratory study in a general population

OBJECTIVE

Nightmares are dysphoric dreams present in both clinical and non-clinical populations. Physiological activity underlies their emotional reactivity. Therefore, the objective of this study was to investigate the role of interoceptive processes (interoceptive sensibility and nociception) in nightmares in the general population.

METHOD

542 French participants were recruited from the general population to complete an online survey. Interoceptive sensibility, nociception, nightmare frequency and nightmare distress were assessed through online scales and questionnaires. Network analysis, regression and mediation analyses were conducted to assess the relationship between these variables.

RESULTS

The results showed the existence of associations between certain dimensions of interoceptive sensibility, nociception, nightmare frequency and nightmare distress. The regression analysis highlighted the involvement of interoceptive dimensions in predicting the nightmare distress score. Mediation analysis highlighted that nociception was a mediating variable in the relationship between nightmare frequency and nightmare distress.

CONCLUSION

This study provides initial evidence in favour of the involvement of interoceptive processes in the understanding of nightmares. These results offer a new window of understanding the etiology of nightmares but also present the interest to target interoceptive processes in the management of nightmares.

A systematic review of new empirical data on lucid dream induction techniques

Lucid dreams are defined as dreams in which the dreamers are aware of the fact that they are dreaming as dreams continue. It has been ~12 years since the last review of the efficiency of lucid dream induction techniques was conducted. Hence, the present study aimed to review the lucid dream induction techniques published in the past decade. The second aim was to propose a modified classification for the existing lucid dream induction techniques, including cognitive techniques, external stimulation, substance intervention, and cortical stimulation. The third aim was to assess the methodological quality of the studies included in the review. It was hypothesised that, comparing with the studies included in the last review, the studies included in the present review had better overall methodological quality. A total of 19 peer-reviewed studies were included and analysed in the present review, from which 14 lucid dream induction techniques were identified. The results indicated that the mnemonic induction of lucid dream technique was the most effective for inducing lucid dreams. Moreover, two new techniques, the senses-initiated lucid dream technique and galantamine intervention, might also be competitive candidates for lucid dream induction but further replications are needed. As hypothesised, the overall methodological quality of the studies included in the present review was higher than that of the studies included the previous review. In all, 17 studies had moderate methodological quality, whereas only three studies had poor methodological quality.

Insomnia symptoms do, but chronotype does not show relevant associations with mental well-being and negative dream experiences

Chronotypes are diversely associated with sleep quality and mental health. Eveningness is generally associated with lower sleep quality and with increased risk for mental health complaints. Along with insomnia symptoms, frequent dysphoric dreams might be key elements of disturbed sleep, and may also indicate psychological imbalance. Our cross-sectional online study aimed to examine whether eveningness can be considered as an independent risk factor of poor mental well-being or whether this association is explained by symptoms of insomnia. Secondly, we examined the associations between eveningness and frequent dysphoric dreaming taking into account the influence of mental well-being and insomnia complaints. Method: We released an online survey with Morningness-Eveningness Questionnaire, Athens Insomnia Scale, General Mental Health, and frequency of dysphoric dreaming: nightmares and bad dreams separately. We analyzed the data of 2077 participants (MAGE = 28.5, SD = 9.6). Eveningness showed a weak but independent association with mental well-being. Additional analyses showed no signs of associations between eveningness and dysphoric dreaming, such as nightmares and bad dreams. The frequency of bad dreams was associated with insomnia complaints and mental well-being, but nightmare frequency was only linked to insomnia symptoms, but not to mental well-being. Insomnia complaints emerged as a more robust factor in poorer mental well-being than the eveningness preference. Eveningness was not associated with dysphoric dreaming. Restoring insomnia might be essential in individuals at risk for mental health complaints.

The role of mindful acceptance and lucid dreaming in nightmare frequency and distress

A theoretical and empirical association between lucid dreaming and mindfulness, as well as lucid dreaming and nightmares has previously been observed; however, the relationship between nightmares and mindfulness has received surprisingly little attention. Here, we present the findings of two studies exploring the relation of nightmare frequency and distress with two components of mindfulness, termed presence and acceptance, as well as lucid dreaming. Study 1 (N = 338) consisted of a low percentage of frequent lucid dreamers whereas Study 2 (N = 187) consisted primarily of frequent lucid dreamers that used lucid dream induction training techniques and meditation. Across studies, nightmare-related variables showed a more robust association with mindful acceptance as opposed to mindful presence. Moreover, individuals with high levels of meditation expertise and practice of lucid dreaming induction techniques reported lower nightmare frequency. Finally, in Study 2, which consisted of frequent lucid dreamers, a positive correlation between lucid dreaming frequency and mindfulness was apparent. The present findings support the notion that wakeful mindfulness is associated with the quality of dreams and extend previous research by suggesting a disentangled role of the two facets of mindfulness in dream variation. This association remains open for experimental manipulation, the result of which could have clinical implications.

Paranormal experiences, sensory-processing sensitivity, and the priming of pareidolia

This investigation tested the effect of priming on pareidolia (the hearing of illusory words in ambiguous stimuli). Participants (41 women, 20 men, mean age 29.95 years) were assigned to primed (n = 30) or unprimed (n = 31) groups: the former were told the study was of ‘purported ghosts voices’, the latter ‘voices in noisy environments.’ Participants were assessed for perception of human voices within recordings of purported electronic voice phenomena (EVP), degraded human speech, normal human speech, and white noise. The primed group had significantly higher perception of voices within EVPs than in degraded speech, this difference was not found for unprimed participants. In contrast to the previous use of this design, the primed group did not have higher perception of voices in EVPs and degraded speech than did the unprimed group. The Aesthetic Sensitivity dimension of the Highly Sensitive Person Scale (HSPS) was associated with detection of degraded stimuli, but not with accuracy of stimulus identification. HSPS score was related to lifetime reporting of anomalous and paranormal experiences. This study partially replicates a paranormal priming effect and shows relationships between HSPS and detection of ambiguous stimuli and anomalous and paranormal experiences.

The heartbeat evoked potential is a questionable biomarker in nightmare disorder: A replication study

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Perogamvros et al. (2013) examined heart beat evoked potential (HEP) in nightmare sufferers.

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Increased HEP was proposed to be a robust biomarker in nightmare disorder.

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We aimed to replicate the original study in two separate and larger databases.

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We did not confirm the original finding showing differential HEP in REM sleep.

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Our data cast doubts on the utility of HEP as a biomarker in nightmare disorder.

Frequent nightmares are highly prevalent and constitute a risk factor for a wide range of psychopathological conditions. Despite its prevalence and clinical relevance however, the pathophysiological mechanisms of nightmares are poorly understood. A recent study (Perogamvros et, al 2019) examined the heart beat evoked potential (HEP) in a small group of nightmare sufferers (N = 11) and matched healthy controls (N = 11) and observed markedly different (Hedges’ g = 1.42 [0.62–2.22]) HEP response across the groups during Rapid Eye Movement (REM) sleep. Moreover, the HEP correlated with depression scores in the nightmare group only. The authors concluded that the HEP in REM sleep could be used as a trait-like biomarker reflecting pathological emotional-and sleep regulation in nightmare disorder. To replicate the above study, we performed the same analyses of HEPs in two separate, and larger databases comprising the polysomnographic recordings of nightmare sufferers and matched controls (N_{Study 1} = 39 ; N_{Study 2} = 41). In contrast to the original findings, we did not observe significant differences in HEP across the two groups in either of the two databases. Moreover, we found no associations between depression scores and HEP amplitudes in the relevant spatiotemporal cluster. Our data cast doubts on the utility of HEP as a biomarker in the diagnostic and treatment procedures of nightmare disorder and suggests that the interpretation of HEP as a marker of impaired arousal and emotional processing during REM sleep is premature and requires further validation.

Has the COVID-19 Pandemic Traumatized Us Collectively? The Impact of the COVID-19 Pandemic on Mental Health and Sleep Factors via Traumatization: A Multinational Survey

PURPOSE

The COVID-19 pandemic affects mental health and sleep, resulting in frequent nightmares. Therefore, identifying factors associated with nightmare frequency is important, as it can indicate mental health issues. The study aimed to investigate increases in nightmare frequency comparing the pre-pandemic and pandemic period, and identify its risk factors. Further, the mediating role of post-traumatic stress disorder symptoms between the pandemic and nightmares is explored.

PATIENTS AND METHODS

For this cross-sectional survey data were obtained via self-rating online survey (ICOSS: details in Partinen et al, 2021), which was open to anyone older than 18 years. The final volunteer sample consisted of 15,292 participants, divided according to their nightmare frequency (high: ≥1-2 nights/week; low: <1-2 nights/week). A total of 9100 participants were excluded if answers on variables of interest were missing or receiving rewards for participation. Chi-square tests identified changes of nightmare frequency. Predictors of high nightmare frequency were assessed using logistic regression and presented as Odds Ratios. Post-hoc mediation models were used to investigate the role of post-traumatic stress symptoms (PTSS).

RESULTS

The mean age was 41.63 (SD=16.55) with 64.05% females. High nightmare frequency increased significantly from 13.24% to 22.35% during the pandemic. Factors associated with it included self-reported PTSS (OR=2.11), other mental disorders and various sleep disorders or problems. Financial burden due to the pandemic, confinement, having had COVID-19, and work situation during the pandemic were associated with nightmare frequency, those relations were partly mediated through PTSS.

CONCLUSION

Our results display the pandemic influence on nightmare frequency, which in turn connects to multiple mental health and sleep factors. These relations were partly mediated through PTSS. The COVID-19 pandemic appears to have caused traumatization of a substantial proportion of society. Health care workers should consider nightmares in their screening routines, as it might indicate PTSS and/or other mental and sleep disorders.

Stuck in a lockdown: Dreams, bad dreams, nightmares, and their relationship to stress, depression and anxiety during the COVID-19 pandemic

BACKGROUND

An upsurge in dream and nightmare frequency has been noted since the beginning of the COVID-19 pandemic and research shows increases in levels of stress, depression and anxiety during this time. Growing evidence suggests that dream content has a bi-directional relationship with psychopathology, and that dreams react to new, personally significant and emotional experiences. The first lockdown experience was an acute event, characterized by a combination of several unprecedent factors (new pandemic, threat of disease, global uncertainty, the experience of social isolation and exposure to stressful information) that resulted in a large-scale disruption of life routines. This study aimed at investigating changes in dream, bad dream and nightmare recall; most prevalent dream themes; and the relationship between dreams, bad dreams, nightmares and symptoms of stress, depression and anxiety during the first COVID-19 lockdown (April-May 2020) through a national online survey.

METHODS

968 participants completed an online survey. Dream themes were measured using the Typical Dreams Questionnaire; stress levels were measured by the Cohen's Perceived Stress Scale; symptoms of anxiety were assessed by Generalized Anxiety Disorder (GAD-7) scale; and symptoms of depression were assessed using the Quick Inventory of Depressive Symptomatology.

RESULTS

34% (328) of participants reported increased dream recall during the lockdown. The most common dream themes were centered around the topics of 1) inefficacy (e.g., trying again and again, arriving late), 2) human threat (e.g., being chased, attacked); 3) death; and 4) pandemic imagery (e.g., being separated from loved ones, being sick). Dream, bad dream and nightmare frequency was highest in individuals with moderate to severe stress levels. Frequency of bad dreams, nightmares, and dreams about the pandemic, inefficacy, and death were associated with higher levels of stress, as well as with greater symptoms of depression and anxiety.

CONCLUSIONS

Results support theories of dream formation, environmental susceptibility and stress reactivity. Dream content during the lockdown broadly reflected existential concerns and was associated with increased symptoms of mental health indices.

Local Neuronal Synchronization in Frequent Nightmare Recallers and Healthy Controls: A Resting-State Functional Magnetic Resonance Imaging Study

Nightmares are highly dysphoric dreams that are well-remembered upon awakening. Frequent nightmares have been associated with psychopathology and emotional dysregulation, yet their neural mechanisms remain largely unknown. Our neurocognitive model posits that nightmares reflect dysfunction in a limbic-prefrontal circuit comprising medial prefrontal and anterior cingulate cortices, hippocampus, and amygdala. However, there is a paucity of studies that used brain imaging to directly test the neural correlates of nightmares. One such study compared the regional homogeneity (ReHo) of resting-state functional magnetic resonance imaging blood-oxygen level-dependent signals between frequent nightmare recallers and controls. The main results were greater regional homogeneity in the left anterior cingulate cortex and right inferior parietal lobule for the nightmare recallers than for the controls. In the present study, we aimed to document the ReHo correlates of frequent nightmares using several nightmare severity measures. We acquired resting-state functional magnetic resonance imaging data from 18 frequent nightmare recallers aged 18-35 (3 males and 15 females) and 18 age- and sex-matched controls, as well as retrospective and prospective disturbed dreaming frequency estimates and scores on the Nightmare Distress Questionnaire. While there were inconsistent results for our different analyses (group comparisons, correlational analyses for frequency estimates/Nightmare Distress scores), our results suggest that nightmares are associated with altered ReHo in frontal (medial prefrontal and inferior frontal), parietal, temporal and occipital regions, as well as some subcortical regions (thalamus). We also found a positive correlation between retrospective disturbed dreaming frequency estimates and ReHo values in the hippocampus. These findings are mostly in line with a recent SPECT study from our laboratory. Our results point to the possibility that a variety of regions, including but not limited to the limbic-prefrontal circuit of our neurocognitive model, contribute to nightmare formation.

Nightmare Distress Questionnaire: associated factors

STUDY OBJECTIVES

The diagnosis of a nightmare disorder is based on clinically significant distress caused by the nightmares, eg, sleep or mood disturbances during the day. The question what factors might be associated with nightmare distress in addition to nightmares frequency is not well studied.

METHODS

Overall, 1,474 persons (893 women, 581 men) completed an online survey. Nightmare distress was measured with the Nightmare Distress Questionnaire.

RESULTS

The findings indicated that nightmare distress, measured by the Nightmare Distress Questionnaire, correlated with a variety of factors in addition to nightmare frequency: neuroticism, female sex, low education, extraversion, low agreeableness, and sensation seeking. Moreover, the percentage of replicative trauma-related nightmares was also associated with higher nightmare distress.

CONCLUSIONS

A large variety of factors are associated with nightmare distress, a finding that is of clinical importance. The construct harm avoidance, however, was not helpful in explaining interindividual differences in nightmare distress. Furthermore, the relationship between nightmare distress and other factors, eg, education or agreeableness, is not yet understood.

Frontal Brain Activity and Subjective Arousal During Emotional Picture Viewing in Nightmare Sufferers

Nightmares are intensely negative dreams that awaken the dreamer. Frequent nightmares are thought to reflect an executive deficit in regulating arousal. Within a diathesis-stress framework, this arousal is specific to negative contexts, though a differential susceptibility framework predicts elevated arousal in response to both negative and positive contexts. The current study tested these predictions by assessing subjective arousal and changes in frontal oxyhemoglobin (oxyHB) concentrations during negative and positive picture-viewing in nightmare sufferers (NM) and control subjects (CTL). 27 NM and 27 CTL subjects aged 18–35 rated subjective arousal on a 1–9 scale following sequences of negative, neutral and positive images; changes in oxyHB were measured by Near-Infrared Spectroscopy (NIRS) using a 2 × 4 template on the frontal pole. Participants also completed the Highly Sensitive Person Scale, a trait marker for differential susceptibility; and completed a dream diary reporting negative and positive dream emotionality. The NM group had higher trait sensitivity, yet higher ratings of negative but not positive emotion in diary dreams. NM compared to CTL subjects reported higher subjective arousal in response to picture-viewing regardless of valence. Dysphoric dream distress, measured prospectively, was negatively associated with frontal activation when viewing negative pictures. Results suggest NM sufferers are highly sensitive to images regardless of valence according to subjective measures, and that there is a neural basis to level of trait and prospective nightmare distress. Future longitudinal or intervention studies should further explore positive emotion sensitivity and imagery in NM sufferers.

Testing the theory of Differential Susceptibility to nightmares: The interaction of Sensory Processing Sensitivity with the relationship of low mental wellbeing to nightmare frequency and nightmare distress

Propensity to have nightmares has been theorised in terms of diathesis-stress models, with this propensity being seen as negative or even pathological. In contrast, a recent model proposes that nightmare propensity is due to Differential Susceptibility to stimuli, where high susceptibility can be beneficial in positive environments but detrimental in negative environments. This susceptibility to stimuli is assessed as the biobehavioural trait Sensory Processing Sensitivity, which refers to a greater responsivity to internal and external stimuli, and an increased depth of cognitive and emotional processing. To test the Differential Susceptibility Framework for nightmares, 137 participants (females = 104, males = 33; mean age = 33.66 years), recruited from a student population and social media sites, were divided into high (n = 39), medium (n = 59) and low (n = 39) Sensory Processing Sensitivity categories based on their score on the Highly Sensitive Person Scale. Low mental wellbeing and the presence of minor psychiatric problems, measured by the General Health Questionnaire, was found to be significantly correlated with nightmare frequency for the high and medium SPS groups (rs = .29 and .28, respectively), but not for the low Sensory Processing Sensitivity group (r = .19). General Health Questionnaire score was also significantly correlated with trait nightmare distress, for the high Sensory Processing Sensitivity group only (r = .32). These findings in favour of the Differential Susceptibility Framework have aetiology and treatment implications for nightmares that differ from diathesis-stress models.

Dream engineering: Simulating worlds through sensory stimulation

We explore the application of a wide range of sensory stimulation technologies to the area of sleep and dream engineering. We begin by emphasizing the causal role of the body in dream generation, and describe a circuitry between the sleeping body and the dreaming mind. We suggest that nearly any sensory stimuli has potential for modulating experience in sleep. Considering other areas that might afford tools for engineering sensory content in simulated worlds, we turn to Virtual Reality (VR). We outline a collection of relevant VR technologies, including devices engineered to stimulate haptic, temperature, vestibular, olfactory, and auditory sensations. We believe these technologies, which have been developed for high mobility and low cost, can be translated to the field of dream engineering. We close by discussing possible future directions in this field and the ethics of a world in which targeted dream direction and sleep manipulation are feasible.

Dream lucidity is associated with positive waking mood

Lucid dreaming is a unique phenomenon with potential applications for therapeutic interventions. Few studies have investigated the effects of lucidity on an individual's waking mood, which could have valuable implications for improving psychological wellbeing. The current experiment aims to investigate whether the experience of lucidity enhances positive waking mood, and whether lucidity is associated with dream emotional content and subjective sleep quality. 20 participants were asked to complete lucid dream induction techniques along with an online dream diary for one week, which featured a 19-item lucidity questionnaire, and subjective ratings of sleep quality, dream emotional content, and waking mood. Results indicated that higher lucidity was associated with more positive dream content and elevated positive waking mood the next day, although there was no relationship with sleep quality. The results of the research and suggestions for future investigations, such as the need for longitudinal studies of lucidity and mood, are discussed.

Nightmares and Stress: A Longitudinal Study

STUDY OBJECTIVES

In nightmare etiology, trait and state factors play important roles. However, the interaction of state and trait factors has never been studied in a longitudinal design.

METHODS

The current sample included 406 pregnant women who were followed up approximately 6 months after giving birth (n = 375) and 4 years later (n = 302). A nightmare frequency scale and several stress-related questionnaires were presented at three measurement points.

RESULTS

Despite the major life events in this sample, nightmare frequency was very stable over this time period and decreased slightly. In line with previous findings, cross-sectional analyses showed that stressors were associated with current nightmare frequency but longitudinal analyses indicated that previously measured nightmare frequency showed even stronger effects on current nightmare frequency.

CONCLUSIONS

Because the nightmare frequencies were very stable, it would be desirable to carry out intervention studies treating nightmares as early as possible-even in childhood-and study whether nightmare occurrence is lower even years after the intervention.

CITATION

Schredl M, Gilles M, Wolf I, Peus V, Scharnholz B, Sütterlin M, Bardtke S, Send TS, Samaras A, Deuschle M. Nightmares and stress: a longitudinal study. J Clin Sleep Med. 2019;15(9):1209-1215.

Nightmare Severity Is Inversely Related to Frontal Brain Activity During Waking State Picture Viewing

STUDY OBJECTIVES

Growing evidence suggests that nightmares have considerable adverse effects on waking behavior, possibly by increasing post-sleep negative emotions. Dysphoric reactions to nightmares are one component of nightmare severity for which the neural correlates are unknown. Here, we investigate possible neural correlates of nightmare severity in a sample of individuals who frequently recall nightmares.

METHODS

Our principal measure of nightmare severity is nightmare distress as indexed by the Nightmare Distress Questionnaire (NDQ), and secondary measures are retrospective and prospective estimates of frequency of recalling dysphoric dreams (DD). We used high-resolution technetium 99m ethyl cysteinate dimer single photon emission computed tomography to assess regional cerebral blood flow (rCBF) while 18 individuals who were frequent nightmare recallers viewed negative and neutral pictures from the International Affective Picture System. We correlated rCBF with NDQ scores and DD recall frequency estimates.

RESULTS

Negative correlations were observed between NDQ scores and rCBF during negative picture viewing in bilateral insula and anterior cingulate, right medial frontal gyrus, bilateral superior temporal gyrus, right inferior frontal and precentral gyri, and bilateral putamen. Retrospective DD recall correlated with rCBF activity primarily in regions overlapping those related to NDQ scores. Prospective DD recall was only weakly related to rCBF. Results for the neutral condition overlapped partially with those for the negative condition; in particular, NDQ and retrospective DD recall were related to rCBF in medial prefrontal and anterior cingulate gyri.

CONCLUSIONS

Results point to a possible overlap in brain mechanisms involved in nightmare dysphoria (during sleep) and distress (during wakefulness) among individuals who frequently recall nightmares. They provide partial support for a neurocognitive model of nightmares.

COMMENTARY

A commentary on this article appears in this issue on page 179.

Increased heartbeat-evoked potential during REM sleep in nightmare disorder

Nightmares are characterized by the experience of strong negative emotions occurring mainly during REM sleep. Some people suffer from nightmare disorder, which is defined by the repeated occurrence of nightmares and by significant distress in wakefulness. Yet, whether frequent nightmares relate to a general increase in emotional reactivity or arousal during sleep remains unclear. To address this question, we recorded heartbeat-evoked potentials (HEPs) during wakefulness, NREM and REM sleep in patients with nightmare disorder and healthy participants. The HEP represents a cortical (EEG) response to the heartbeat and indexes brain-body interactions, such as interoceptive processing and intrinsic levels of arousal. HEP amplitude is typically increased during states of high emotional arousal and motivation, and is decreased in depression. Here we compared the amplitude of HEPs between nightmare patients and healthy controls separately during AWAKE, NREM, REM periods, and found higher HEP amplitude in nightmare patients compared to healthy controls over a cluster of frontal regions only during REM sleep. This effect was not paralleled by any group difference in cardiac control measures (e.g. heart rate variability, interbeat interval). These findings corroborate the notion that nightmares are essentially a REM pathology and suggest that increased emotional arousal during REM sleep, as measured by HEP, is a physiological condition responsible for frequent nightmares. This result also supports that HEP may be used as a biomarker of increased emotional and sensory processing during REM sleep in these patients.

Aetiology and treatment of nightmare disorder: State of the art and future perspectives

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.

Sleep spindles are altered in early- but not late-onset nightmare recallers

Nightmares are a common sleep disorder, defined as highly disturbing mentation which usually awakens the individual from rapid eye movement (REM) sleep. While nightmares are mainly a REM sleep phenomenon, Picard-Deland et al., (2017) recently showed an association between nightmare recall and sleep spindles, which are a non-rapid eye movement (NREM) oscillatory feature. Their results pointed to fewer slow spindles and a higher oscillatory frequency for fast spindles among frequent nightmare recallers compared with controls. To test the suggestion that nightmares stem from changes to emotional neural circuits arising in early childhood (Nielsen, 2017), including early changes in sleep spindles (Scholle et al., 2007), we investigated if the spindle features of early-onset nightmare recallers (ie, recalling nightmares since childhood) (N = 22), differed from those of late-onset nightmare recallers (ie, since adolescence or adulthood) (N = 11), or from those of controls (N = 23). A retrospective analysis of the sleep spindles of 56 participants who had undergone a polysomnographically-recorded morning nap revealed that Early starters uniquely exhibited lower slow spindle densities in five of six derivations (all p < 0.045) and higher fast spindle frequencies in all six derivations (all p < 0.015). These results add precision to previously reported findings for Nightmare recallers: spindle differences are shown to hold only for Early starters. The lifelong occurrence of nightmares may be closely tied to disruptions in the normal development of spindle generation processes occurring early in development.