Individuals who frequently experience nightmares report compromised sleep quality, poor daytime mood, and functioning. Previous research has aimed at linking these impairments with altered sleep architecture, but results were inconclusive. One plausible explanation is that only a few studies recorded markers of autonomic nervous system activity. For the first time, this study collected such markers under ecologically valid conditions with ambulatory assessment. In 19 individuals with frequent nightmares (≥1 nightmare/week) and 19 healthy control participants (<1 nightmare/month), measures indicating autonomic activation (heart rate, heart rate variability, respiration cycle length, electrodermal fluctuations, EEG arousals, saliva cortisol, REM density) were collected while applying ambulatory polysomnographic assessment during 3 consecutive nights. When nightmare participants reported a nightmare, we analyzed the last 5 min of REM sleep before awakening and compared these data to their non‐nightmares as well as to the dream episodes of control participants. Overall, there were no general differences in autonomic activation of nightmare sufferers compared to control participants. However, when nightmare participants experienced nightmares, autonomic activation was markedly increased compared to their own non‐nightmares and, to some extent, to control participant’s dreams. Significant intraindividual differences were found for all autonomic measures except in participant’s EEG arousals and cortisol levels. Group differences were found in EEG arousals and heart rate. In conclusion, ambulatory polysomnography demonstrates that nightmares are accompanied by increased autonomic activation. Results support the notion of impaired self‐reported sleep quality caused by one’s autonomic response rather than altered sleep pattern.

SUMMARYLittle is known about the relation between pineal volume and insomnia. Melatonin promotes sleep processes and, administered as a drug, it is suitable to improve primary and secondary sleep disorders in humans. Recent magnetic resonance imaging studies suggest that human plasma and saliva melatonin levels are partially determined by the pineal gland volume. This study compares the pineal volume in a group of patients with primary insomnia to a group of healthy people without sleep disturbance. Pineal gland volume (PGV) was measured on the basis of high-resolution 3 Tesla MRI (T1-magnetization prepared rapid gradient echo) in 23 patients and 27 controls, matched for age, gender and educational status. Volume measurements were performed conventionally by manual delineation of the pineal borders in multi-planar reconstructed images. Pineal gland volume was significantly smaller (P < 0.001) in patients (48.9 AE 26.6 mm 3 ) than in controls (79 AE 30.2 mm 3 ). In patients PGV correlated negatively with age (r = À0.532; P = 0.026). Adjusting for the effect of age, PGV and rapid eye movement (REM) latency showed a significant positive correlation (r S = 0.711, P < 0.001) in patients. Pineal volume appears to be reduced in patients with primary insomnia compared to healthy controls. Further studies are needed to clarify whether low pineal volume is the basis or the consequence of functional sleep changes to elucidate the molecular pathology for the pineal volume loss in primary insomnia.

BackgroundNightmares and bad dreams are common in people with emotional disturbances. For example, nightmares are a core symptom in posttraumatic stress disorder and about 50% of borderline personality disorder patients suffer from frequent nightmares. Independent of mental disorders, nightmares are often associated with sleep problems such as prolonged sleep latencies, poorer sleep quality, and daytime sleepiness. It has not been well documented whether this is reflected in objectively quantifiable physiological indices of sleep quality.MethodsQuestionnaires regarding subjective sleep quality and ambulatory polysomnographic recordings of objective sleep parameters were collected during three consecutive nights in 17 individuals with frequent nightmares (NM) and 17 healthy control participants (HC).ResultsNM participants reported worse sleep quality, more waking problems and more severe insomnia compared to HC group. However, sleep measures obtained by ambulatory polysomnographic recordings revealed no group differences in (a) overall sleep architecture, (b) sleep cycle duration as well as REM density and REM duration in each cycle and (c) sleep architecture when only nights with nightmares were analyzed.ConclusionsOur findings support the observation that nightmares result in significant impairment which is independent from disturbed sleep architecture. Thus, these specific problems require specific attention and appropriate treatment.

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Despite the large number of studies addressing gender differences in dream recall and dream content, research regarding whether these differences might be affected by sex role orientation is rather scarce. The present online-survey included a large sample of most recent dreams. The results clearly indicate that sex role orientation (femininity/expressivity and masculinity/instrumentality) affect the same dream characteristics that show marked gender differences (e.g., sexual dream content, physical aggression). Whereas the effect of sex role orientation on dream content support the continuity hypothesis of dreaming, the effect of biological sex on dream content does not exclude that other variables (such as, for example, the amount of sexual fantasies during waking) have an effect on dream content in addition to sex role orientation. Thus, future studies have to elicit more waking-life variables in order to model the varying daytime experiences of men and women in order to investigate whether these daytime differences sufficiently explain gender differences in dreaming or whether biological factors are also of importance.

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Previous research found that nightmares are accompanied by strong negative emotions. However, nonnightmare dream content of individuals who frequently suffer from nightmares has never been examined. Eighteen individuals with frequent nightmares ($1 nightmare/week) and 18 control participants without nightmares (,1 nightmare/month) were examined while sleeping at home in their usual environment with an ambulatory polysomnographic sleep recording system attached. They were asked to report dream content after spontaneous awakenings during 3 consecutive nights. This resulted in 157 dream reports that were subjected to dream content analysis by 2 trained research assistants. We compared nightmare and especially nonnightmare dream content and emotions within the nightmare group, as well as between nightmare and control participants. Also, we quantified references to the research setting in the dream reports. Results revealed more negative and fewer positive emotions in nonnightmare dreams of the nightmare group compared with the control group, even when waking anxiety scores were controlled for. Nightmares were rated as containing more negative affect and more anxiety compared with both, matched nonnightmare dreams of the same individuals and normal dreams of control participants. Furthermore, dreams of individuals who suffer from frequent nightmares contained fewer dream characters compared with control participants' dreams. Considerably fewer references to the research setting were found compared with prior sleep laboratory studies on dream content. In conclusion, it was found that individuals who frequently suffer from nightmares also experience their usual nonnightmare dreams as more negatively toned.

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