SummaryBackgroundSleep difficulties might be a contributory causal factor in the occurrence of mental health problems. If this is true, improving sleep should benefit psychological health. We aimed to determine whether treating insomnia leads to a reduction in paranoia and hallucinations.MethodsWe did this single-blind, randomised controlled trial (OASIS) at 26 UK universities. University students with insomnia were randomly assigned (1:1) with simple randomisation to receive digital cognitive behavioural therapy (CBT) for insomnia or usual care, and the research team were masked to the treatment. Online assessments took place at weeks 0, 3, 10 (end of therapy), and 22. The primary outcome measures were for insomnia, paranoia, and hallucinatory experiences. We did intention-to-treat analyses. The trial is registered with the ISRCTN registry, number ISRCTN61272251.FindingsBetween March 5, 2015, and Feb 17, 2016, we randomly assigned 3755 participants to receive digital CBT for insomnia (n=1891) or usual practice (n=1864). Compared with usual practice, the sleep intervention at 10 weeks reduced insomnia (adjusted difference 4·78, 95% CI 4·29 to 5·26, Cohen's d=1·11; p<0·0001), paranoia (−2·22, −2·98 to −1·45, Cohen's d=0·19; p<0·0001), and hallucinations (−1·58, −1·98 to −1·18, Cohen's d=0·24; p<0·0001). Insomnia was a mediator of change in paranoia and hallucinations. No adverse events were reported.InterpretationTo our knowledge, this is the largest randomised controlled trial of a psychological intervention for a mental health problem. It provides strong evidence that insomnia is a causal factor in the occurrence of psychotic experiences and other mental health problems. Whether the results generalise beyond a student population requires testing. The treatment of disrupted sleep might require a higher priority in mental health provision.FundingWellcome Trust.

SUMMAR Y Nightmares can be defined as very disturbing dreams, the events or emotions of which cause the dreamer to wake up. In contrast, unpleasant dreams can be defined in terms of a negative emotional rating of a dream, irrespective of whether or not the emotions or events of the dream woke the dreamer. This study addresses whether frequency of unpleasant dreams is a better index of low well-being than is frequency of nightmares. A total of 147 participants reported their nightmare frequency retrospectively and then kept a log of all dreams, including nightmares, for 2 weeks, and rated each dream for pleasantness/unpleasantness. Anxiety, depression, neuroticism, and acute stress were found to be associated with nightmare distress (ND) (the trait-like general level of distress in waking-life caused by having nightmares) and prospective frequency of unpleasant dreams, and less so with the mean emotional tone of all dreams, or retrospective or prospective nightmare frequency. Correlations between low well-being and retrospective nightmare frequency became insignificant when trait ND was controlled for, but correlations with prospective unpleasant dream frequency were maintained. The reporting of nightmares may thus be confounded and modulated by trait ND: such confounding does not occur for the reporting of unpleasant dreams in general. Thus there may be attributional components to deciding that one has been awoken by a dream, which can affect estimated nightmare frequency and its relationship with well-being. Underestimation of nightmare frequency by the retrospective questionnaire compared with logs was found to be a function of mean dream unpleasantness and ND.k e y w o r d s definition of nightmares, nightmare distress, nightmare frequency, psychopathology, well-being

Incorporation of details from waking life events into Rapid Eye Movement (REM) sleep dreams has been found to be highest on the night after, and then 5-7 nights after events (termed, respectively, the day-residue and dream-lag effects). In experiment 1, 44 participants kept a daily log for 10 days, reporting major daily activities (MDAs), personally significant events (PSEs), and major concerns (MCs). Dream reports were collected from REM and Slow Wave Sleep (SWS) in the laboratory, or from REM sleep at home. The dream-lag effect was found for the incorporation of PSEs into REM dreams collected at home, but not for MDAs or MCs. No dream-lag effect was found for SWS dreams, or for REM dreams collected in the lab after SWS awakenings earlier in the night. In experiment 2, the 44 participants recorded reports of their spontaneously recalled home dreams over the 10 nights following the instrumental awakenings night, which thus acted as a controlled stimulus with two salience levels, high (sleep lab) and low (home awakenings). The dream-lag effect was found for the incorporation into home dreams of references to the experience of being in the sleep laboratory, but only for participants who had reported concerns beforehand about being in the sleep laboratory. The delayed incorporation of events from daily life into dreams has been proposed to reflect REM sleep-dependent memory consolidation. However, an alternative emotion processing or emotional impact of events account, distinct from memory consolidation, is supported by the finding that SWS dreams do not evidence the dream-lag effect.

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In four sleep loss experiments we aimed, first, to compare performance during long-term sleep reduction with performance during short-term total sleep deprivation, and second, to measure the effects of both methods of sleep loss on ability to ignore distracting irrelevant stimuli, using a hding embedded figures test (FEFT). Logical reasoning, auditory vigdance and finding embedded figures tasks were shown to be significantly sensitive to one night's sleep deprivation. However, in one sleep reduction study subjects reduced to a mean of 5.2 hours sleep per night for 4 weeks showed no performance deficits on logical reasoning. In a second sleep reduction study subjects reduced to a mean of 4.3 hours sleep per night for 4 nights, and subjects reduced to a mean of 5.3 hours sleep per night for 18 nights, showed no performance deficits on logical reasoning or auditory vigilance, despite their reports of severe increases in subjective sleepiness and reduced concentration. Both these sleep reduction groups, though, did show decrements on the FEFT, which we interpret in terms of dearousal increasing distractibility, which the sleep-reduced subjects could not overcome with effort, as they did with the other tests.A paradox within sleep loss research is that studies on subjects having one night's total sleep deprivation show deficits on certain tasks, some lasting for 10 min or less (Donnell, 1969;Glenville, Broughton, Wing, and Wilkinson, 1978;Wilkinson, 1961; Wimmer, Hoffmann, Bonato, and Moffitt, 1992), whereas long-term sleep reduction of a few hours per night is often found to result in no performance deficit (Horne, 1988a; Horne and Wilkinson, 1985).Single experiments usually look at just one of these methods of losing sleep. In this paper our first aim was to investigate groups of subjects under different conditions of sleep loss, but using the same tests, so that comparisons between the conditions could be made. Comparisons would be between different levels of sleep reduction, and between long-term reduction and short-term total sleep deprivation. This type of comparison had previously been performed over two nights by Wilkinson (1968), using six different levels of sleep length. He found that performance deficits result when subjects have 3 h sleep over one night, or 5 h sleep over two nights, which indicates that sleep loss can accumulate. He indicated, however, that as long as

This study investigates evidence, from dream reports, for memory consolidation during sleep. It is well-known that events and memories from waking life can be incorporated into dreams. These incorporations can be a literal replication of what occurred in waking life, or, more often, they can be partial or indirect. Two types of temporal relationship have been found to characterize the time of occurrence of a daytime event and the reappearance or incorporation of its features in a dream. These temporal relationships are referred to as the day-residue or immediate incorporation effect, where there is the reappearance of features from events occurring on the immediately preceding day, and the dream-lag effect, where there is the reappearance of features from events occurring 5–7 days prior to the dream. Previous work on the dream-lag effect has used spontaneous home recalled dream reports, which can be from Rapid Eye Movement Sleep (REM) and from non-Rapid Eye Movement Sleep (NREM). This study addresses whether the dream-lag effect occurs only for REM sleep dreams, or for both REM and NREM stage 2 (N2) dreams. 20 participants kept a daily diary for over a week before sleeping in the sleep laboratory for 2 nights. REM and N2 dreams collected in the laboratory were transcribed and each participant rated the level of correspondence between every dream report and every diary record. The dream-lag effect was found for REM but not N2 dreams. Further analysis indicated that this result was not due to N2 dream reports being shorter, in terms of number of words, than the REM dream reports. These results provide evidence for a 7-day sleep-dependent non-linear memory consolidation process that is specific to REM sleep, and accord with proposals for the importance of REM sleep to emotional memory consolidation.

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Using the Gudjonsson Suggestibility Scale, individuals who had not slept for 43 hours showed significantly greater yield to leading questions about a story than did controls. When questioned again following negative feedback, they tended to change their answers more than controls. Individuals who had not slept for 21 hours showed a trend for greater suggestibility. Sleep-deprived individuals scored lower on the Profile of Mood States Energetic, Clearheaded, and Confident scales than did controls. Sleep-deprived individuals thus have reduced cognitive ability or motivation to discriminate and detect discrepancies between original and misleading information. Therefore, it is recommended that police interrogation not occur if the interviewee has been deprived of sleep.