A Neurocomputational Theory of Nightmares: The role of formal properties of nightmare images

Study Objectives To test and extend Levin & Nielsen’s (2007) Affective Network Dysfunction (AND) model with nightmare disorder (ND) image characteristics, and then to implement the extension as a computational simulation, the Disturbed Dreaming Model (DDM). Methods We used AnyLogic V7.2 to computationally implement an extended AND model incorporating quantitative effects of image characteristics including valence, dominance, and arousal. We explored the DDM parameter space by varying parameters, running approximately one million runs, each for one month of model time, varying pathway bifurcation thresholds, image characteristics, and individual-difference variables to quantitively evaluate their combinatory effects on nightmare symptomology. Results The DDM shows that the AND model extended with pathway bifurcations and image properties is computationally coherent. Varying levels of image properties we found that when nightmare images exhibit lower dominance and arousal levels, the ND agent will choose to sleep but then has a traumatic nightmare, whereas, when images exhibit greater than average dominance and arousal levels, the nightmares trigger sleep-avoidant behavior, but lower overall nightmare distress at the price of exacerbating nightmare effects during waking hours. Conclusions Computational simulation of nightmare symptomology within the AND framework suggests that nightmare image properties significantly influence nightmare symptomology. Computational models for sleep and dream studies are powerful tools for testing quantitative effects of variables affecting nightmare symptomology and confirms the value of extending the Levin & Nielsen AND model of disturbed dreaming/ND.

Prevalence and Detailed Experience of Nightmare and Nightmare Disorder in Chinese University Students

Nightmares influence the mental health of university students, but the prevalence of nightmare and nightmare disorder requires additional documentation. The data of detailed nightmare experience of nightmare disorder and related depressive mood in this population are also scarce. First, a total of 1,451 students in a comprehensive Chinese university were invited to report their nightmare frequency. Sixty-eight patients with nightmare disorder were diagnosed using a semi-structured clinical interview according to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013). Second, 60 patients with nightmare disorder (8 of 68 patients were dismissed due to data incompletion) and 124 gender-matched, healthy students were invited to answer the Nightmare Experience Questionnaire (NEQ) and the Plutchik-van Praag Depression Inventory (PVP). Of 1,451 students, 923 reported nightmares (its annual prevalence was 63.61%), and 68 were diagnosed with nightmare disorder (its prevalence was 4.69%), with a female preponderance. The mean PVP and four NEQ scale scores in patients were higher than those in healthy students. The PVP scores were correlated with NEQ Physical Effect in patients, and with Negative Emotion in healthy students. This is the first report regarding nightmare disorder prevalence and detailed nightmare experience in university students. The findings of a high prevalence of nightmare disorder in women and elevated scores of nightmare experience among patients in the university population might help address the mechanisms and the management of patients with nightmare disorder.

Imagery Rescripting and Imaginal Exposure in Nightmare Disorder Compared to Positive Imagery: A Randomized Controlled Trial

<b><i>Introduction:</i></b> Both imagery rescripting and imaginal exposure have been proven to be effective in the treatment of chronic nightmares when compared to a waitlist condition. Little is known about their comparative efficacy and their efficacy compared to an active control. <b><i>Objective:</i></b> The aims of this study were to compare the two treatments to one another and to positive imagery as an active control, and to explore covariates of the treatment effect. <b><i>Methods:</i></b> In this single-blinded randomized controlled trial, 96 patients with nightmare disorder (idiopathic nightmares) from an outpatient clinic were randomly assigned to a single individual treatment session of rescripting, exposure, or positive imagery and 4 weeks of practice at home. The primary outcome was nightmare distress, and the secondary outcomes were nightmare frequency, nightmare effects, self-efficacy, and general psychopathology. <b><i>Results:</i></b> Nightmare distress was reduced in all groups (imagery rescripting: Cohen’s <i>d</i> = –1.04, imaginal exposure: <i>d</i> = –0.68, positive imagery: <i>d</i> = –0.57), as were nightmare frequency, nightmare effects, and psychopathology. Self-efficacy was enhanced. No differential treatment effects were found on any primary or secondary measure. Treatment gains were not associated with demographic or disorder characteristics, baseline values, treatment credibility, or the number of practice sessions. <b><i>Conclusions:</i></b> Even short nightmare treatments are effective regardless of personal characteristics, and different interventions produce similar results. Future research should aim to clarify the mechanisms of action. Health care should make more use of these powerful and easy-to-administer nightmare treatments.

The Nightmare Disorder Index: development and initial validation in a sample of nurses

Study Objectives Nurses are a group at high risk for nightmares, yet little is known about the rate of nightmare disorder and associated psychosocial factors in this group in part attributable to the lack of a self-report questionnaire to assess DSM-5 criteria for nightmare disorder. Aims of the current study were to (1) report on development and initial validity of a self-report measure of DSM-5 nightmare disorder, and (2) examine the rate and associated factors of nightmare disorder among nurses. Methods Nurses (N = 460) completed baseline measures online including Nightmare Disorder Index (NDI), psychosocial and demographic questionnaires. A subset (n = 400) completed 14 days of sleep diaries and actigraphy. Results NDI demonstrated satisfactory psychometric characteristics as indicated by good internal consistency (α = 0.80), medium inter-item correlations (r = 0.50), medium to large item-total (r = 0.55–0.85) and convergent correlations (0.32–0.45), and small to medium discriminant correlations (–0.12–0.33). Per NDI, 48.7% of nurses reported no nightmares in the past month, 43.9% met partial/subthreshold criteria and 7.4% met full criteria for probable nightmare disorder. Nurses with nightmare disorder demonstrated significantly poorer psychosocial functioning (i.e. posttraumatic stress, depression, anxiety, stress) than those with subthreshold nightmare symptoms, who had poorer functioning than those with no nightmares. Conclusions NDI is an efficient and valid self-report assessment of nightmare disorder. Nurses have high rates of nightmares and nightmare disorder which are associated with poorer psychosocial functioning. We recommend increased nightmare screening particularly for high-risk populations such as healthcare workers.

Nightmare Disorder and Isolated Sleep Paralysis

Nightmare disorder and recurrent isolated sleep paralysis are rapid eye movement (REM) parasomnias that cause significant distress to those who suffer from them. Nightmare disorder can cause insomnia due to fear of falling asleep through dread of nightmare occurrence. Hyperarousal and impaired fear extinction are involved in nightmare generation, as well as brain areas involved in emotion regulation. Nightmare disorder is particularly frequent in psychiatric disorders and posttraumatic stress disorder. Nonmedication treatment, in particular imagery rehearsal therapy, is especially effective. Isolated sleep paralysis is experienced at least once by up to 40% of the general population, whereas recurrence is less frequent. Isolated sleep paralysis can be accompanied by very intense and vivid hallucinations. Sleep paralysis represents a dissociated state, with persistence of REM atonia into wakefulness. Variations in circadian rhythm genes might be involved in their pathogenesis. Predisposing factors include sleep deprivation, irregular sleep–wake schedules, and jetlag. The most effective therapy consists of avoiding those factors.

Bad dreams, bedtime anxiety, and trait anxiety in school-aged children

Background and objectives Occasional nightmares (distressing dreams that awaking the sleeper) and bad dreams (distressing dreams that do not awaking the sleeper) are very common in children and adolescents. About 5% of children experience frequent nightmares (once a week or more often) and the question arises as to what factors contribute to significant nightmare distress which is basic for diagnosing a nightmare disorder. Materials and methods A sample of 624 school-aged children (10–16 years; mean age 12.45 ± 1.33 years) completed a dream questionnaire and an anxiety inventory. Results About 11% of the participants reported frequent bad dreams; 3.5% reported frequent bedtime anxieties due to bad dreams. Similar to the findings in adults, distress due to bad dreams was not only related to bad dream frequency but also to trait anxiety—controlling for the direct effect of trait anxiety on bad dream frequency, i.e., bad dream frequency and trait anxiety contributed independently to bedtime anxiety due to bad dreams. In the exploratory part, the cultural background of the children’s parents showed only minor effects on bad dreams. Conclusion Similar to nightmare studies in adults, bad dream frequency and trait anxiety contributed independently to bad dream distress. Based on the current diagnostic criteria of the nightmare disorder, it would be interesting to have the opportunity to treat children with significant distress due to nightmares or bad dreams and study the long-term benefit—given that many adult nightmare sufferers reported that their nightmares started in childhood.

Nightmare experience and personality disorder functioning styles in healthy volunteers and nightmare disorder patients

Nightmares are prevalent in psychiatric disorders, and personality disorder features might be associated with nightmare experience, especially in nightmare disorder patients. The authors invited 219 healthy volunteers and 118 nightmare disorder patients to undergo tests of the Nightmare Experience Questionnaire (NEQ), the Parker Personality Measure (PERM), and the Plutchik-van Praag Depression Inventory. Compared to healthy volunteers, nightmare disorder patients scored significantly higher on annual nightmare frequency and NEQ Physical Effect, Negative Emotion, Meaning Interpretation, and Horrible Stimulation, and higher on PERM Paranoid, Schizotypal, Borderline, Histrionic, Narcissistic, Avoidant, and Dependent styles. Borderline, Schizotypal, and Passive-Aggressive styles in healthy volunteers and Dependent, Avoidant, Histrionic, and Paranoid in patients were significant predictors of some NEQ scales. Higher annual nightmare frequency, higher scale scores of nightmare experience and personality disorder styles, and more associations between the two were found in nightmare disorder patients, implying the need for personality-adjustment therapy for nightmare disorder.