Nightmares are common, occurring weekly in 4%-10% of the population, and are associated with female gender, younger age, increased stress, psychopathology, and dispositional traits. Nightmare pathogenesis remains unexplained, as do differences between nontraumatic and posttraumatic nightmares (for those with or without posttraumatic stress disorder) and relations with waking functioning. No models adequately explain nightmares nor have they been reconciled with recent developments in cognitive neuroscience, fear acquisition, and emotional memory. The authors review the recent literature and propose a conceptual framework for understanding a spectrum of dysphoric dreaming. Central to this is the notion that variations in nightmare prevalence, frequency, severity, and psychopathological comorbidity reflect the influence of both affect load, a consequence of daily variations in emotional pressure, and affect distress, a disposition to experience events with distressing, highly reactive emotions. In a cross-state, multilevel model of dream function and nightmare production, the authors integrate findings on emotional memory structures and the brain correlates of emotion.Keywords: nightmares, distress, neurophysiology of fear memory, posttraumatic stress disorder, psychopathology Nightmares are the most common form of disturbed dreaming. Vivid, with emotions escalating at times to the brink of terror, they are manifestations of the dramatic autonomic and cognitive fluctuations that can arise during rapid eye movement (REM) sleep and, under certain circumstances, during Stage 2 sleep. Nightmares can be simple and benign or so emotionally severe that they beg for comparison with psychotic episodes (C. Fisher, Byrne, Edwards, & Kahn, 1970;Hartmann, 1984;Sullivan, 1962). Occasional nightmares are almost ubiquitous in the general population. However, frequent distressing nightmares are more common than generally thought, affecting 4%-10% of individuals by conservative estimates. Nightmares are also extremely common following trauma exposure. Posttraumatic nightmares may depict traumarelated content and, in cases of chronic posttraumatic stress disorder (PTSD), may at times replicate the trauma with great distress (for review, see Mellman & Pigeon, 2005).There has been a proliferation of experimental work on posttraumatic and nontraumatic nightmares in the past 15 years, the vast majority of which has examined the psychopathological correlates of individuals with frequent nightmares. Furthermore, recent advances in neuroscience have greatly expanded our understanding of dreaming and related brain functions (Maquet, 2000;Maquet et al., 2000) as well as the pathogenic mechanisms implicated in fear conditioning and the development of PTSD (LeDoux, 2000;Ohman & Mineka, 2001). However, despite the clear implications of these developments for understanding nightmares, there are still no comprehensive models of nightmare etiology and no conceptual frameworks for understanding the link between posttraumatic and nontraumatic nightm...

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Self-reports of nightmare frequency were collected in seven independent nonclinical populations (n = 3433). In addition, sleep and dreaming characteristics of frequent nightmare subjects and low-nightmare controls were compared in three smaller subsamples. Reporting rates of nightmare occurrence were remarkably stable with females reporting significantly more nightmare attacks (p < .001) than males. Analysis of sleep and dreaming parameters reliably differentiated nightmare reporters from low-nightmare controls on a number of measures. Nightmare subjects rated their sleep quality as poorer (p < .05), had greater dream recall (p < .001), were more affected by their dreams (p < .001) and nightmares (p < .001), and reported more aggression in their dreams (p < .001) than controls. Thus, nightmare sufferers appear to be significantly more internally directed and more sensitive to their generalized dreaming states. The results are discussed within the context of Hartmann's (1984) nightmare theory.

Self-reported sleep complaints and current cognitive functioning were assessed in 375 nondemented participants ages 75 to 85 years (134 men and 241 women) as part of enrollment in the Bronx aging study, an ongoing longitudinal community-based study of cognitive aging. This study only reports on the baseline data collected from 1980 to 1983. Sleep complaints were common, occurring in about 25% of the sample. Furthermore, after controlling for depression, use of hypnotic medication, physical morbidity, age, and education, participants who reported longer sleep onset latencies performed significantly worse on measures of verbal knowledge, long-term memory and fund of information, and visuospatial reasoning. Participants who reported longer sleep durations did significantly worse on a measure of verbal short-term memory. These results suggest that perceived sleep is related to select objective cognitive abilities even when accounting for commonly recognized mediating variables, such as depression, medical comorbidity, age, or use of hypnotic medication. Given the restricted range of this nondemented sample, these results may underestimate the relation between cognitive abilities and sleep.

In order to explore the proposed relationship between nightmare occurrence and schizotypy, 30 frequent-nightmare subjects (at least one occurrence per week) and 30 low-nightmare controls, all of whom were female college students, were compared on several converging measures of schizotypal signs and behaviors. Consistent with previous research, frequent nightmare subjects demonstrated greater deviance on psychometric scales of schizotypy, and reported significantly greater schizotypal symptomatology on a structured clinical interview, than controls did. In addition, nightmare subjects produced similar electrodermal habituation patterns to auditory orienting stimuli as those that have been documented in schizophrenia-spectrum disorders. The results suggest that nightmare experience may be a useful conjoint behavioral indicator for the early detection of schizophrenia-spectrum psychopathology.

Nightmares—vivid, emotionally dysphoric dreams—are quite common and are associated with a broad range of psychiatric conditions. However, the origin of such dreams remains largely unexplained, and there have been no attempts to reconcile repetitive traumatic nightmares with nontraumatic nightmares, dysphoric dreams that do not awaken the dreamer, or with more normative dreams. Based on recent research in cognitive neuroscience, sleep physiology, fear conditioning, and emotional-memory regulation, we propose a multilevel neurocognitive model that unites waking and sleeping as a conceptual framework for understanding a wide spectrum of disturbed dreaming. We propose that normal dreaming serves a fear-extinction function and that nightmares reflect failures in emotion regulation. We further suggest that nightmares occur as a result of two processes that we term affect load—a consequence of daily variations in emotional pressures—and affect distress—a disposition to experience events with high levels of negative emotional reactivity.

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This investigation examined the proposed relationship between nightmare frequency and ego boundary impairment (Hartmann, 1984) in a sample of female college students. Thirty frequent nightmare sufferers (at least one attack per week) and 30 controls (maximum of one nightmare per year) were compared. In order to measure ego boundary impairment, the Rorschach inkblot test was administered and scored for barrier and penetration responses (Fisher & Cleveland, 1968) and indices of thought disorder (Blatt & Ritzier, 1974). An ego boundary questionnaire developed by Hartmann and colleagues (Hartmann, 1989;Hartmann et al., 1987) was also administered. Although barrier and penetration scores did not discriminate, the frequent-nightmare subjects demonstrated more disordered thinking on the Rorschach (p < .001) and greater boundary impairment on the questionnaire (p < .001), providing empirical support for Hartmann's nightmare hypothesis. The results are discussed within the framework of psychoanalytic object-relations theory.The term nightmare has often been used to describe a vivid and terrifying nocturnal episode in which the dreamer is abruptly awakened from sleep. So severe is the full-blown nightmare that it has been described as a brief yet reversible acute psychotic episode (Detre & Jarecki, 1971;Fisher, Byrne, Edwards, & Kahn, 1970;Hartmann, 1984;Mack, 1970). Indeed, Sullivan (1962) once stated that "terror dreams . . . are so closely related to schizophrenic panic states that it does violence to scientific method to arbitrarily separate the two groups" (p. 161).Nightmares differ from anxiety dreams in that they invariably result in sleep interruption. They differ from the more severe night terror attacks in that they are rapid eye movement (REM)-sleep dreams that are marked by a subjective Requests for reprints should be sent to