The practice of Daylight Saving Time in Canada: Its suitability with respect to sleep and circadian rhythms.

Daylight Saving Time (DST) is the practice of setting the clocks one hour forward from Standard Time (ST) in the spring and back again to ST in the fall. This commentary discusses the impact of bi-annual time changes on sleep and circadian rhythms and suggests avenues to minimize negative outcomes on the well-being of Canadian citizens. Ideally, ST should be close to solar time, meaning that daylight is equally distributed before and after noon time, i.e., when the sun is at its highest point in the sky. In Canada, some provinces are proposing to opt out of DST to either return to constant ST throughout the year or to implement permanent DST. National and international associations of clinicians and researchers on sleep and biological rhythms and in health sciences have positioned themselves in favour of permanent ST. In Canada, the Canadian Sleep Society and the Canadian Society for Chronobiology have also issued such a position. This commentary focuses on the implications of previous research findings for sleep and health in Canada given its northern geographical location. It concludes with a research agenda focusing on the Canadian context.

RéSUMé: L'heure avancée (HA) consiste à avancer les horloges d'une heure par rapport à l'heure normale (HN) au printemps et à revenir à l'HN à l'automne. Le but de ce commentaire est de traiter de l'impact des changements d'heure semestriels sur le sommeil et les rythmes circadiens et de proposer des moyens d'en minimiser les conséquences négatives sur le bien-être des citoyens canadiens. Idéalement, l'HN devrait être proche de l'heure solaire, ce qui signifie que la lumière du jour est répartie de manière égale avant et après midi, c'est-à-dire lorsque le soleil est à son point culminant dans le ciel. Au Canada, certaines provinces proposent de renoncer à la pratique du changement d'heure pour revenir à une HN constante tout au long de l'année ou mettre en place l'HA de façon permanente. Des associations nationales et internationales de cliniciens et de chercheurs sur le sommeil, les rythmes biologiques et les sciences de la santé se sont prononcées en faveur de l'HN permanente. Au Canada, la Société canadienne du sommeil et la Société canadienne de chronobiologie ont adopté la même position. Le commentaire est centré sur les retombées des résultats de recherches antérieures pour le sommeil et la santé au Canada, compte tenu de sa situation géographique nordique. Il se termine par un programme de recherche axé sur le contexte canadien.

Creation of a shortened version of the Sleep Disorders Questionnaire (SDQ).

The 176-item Sleep Disorders Questionnaire (SDQ) was initially developed using canonical discriminant function analysis on 4 groups of sleep disorder patients, but it was never studied by factor analysis in its entirety. Several authors have criticized 2 of its subscales as being confounded with each other, and its narcolepsy scale as substantially over-diagnosing narcolepsy. This study describes its first exploratory factor analysis (EFA), the intent of which was to reassess item membership on the 4 existing subscales and to derive new scales to improve differential diagnosis between patient groups. It was also hoped that EFA could reduce the total number of questions, to increase speed of completion. The EFA was performed on the anonymized SDQ results from a retrospective review of the charts of 2131 persons from 7 sleep disorders clinics and research centers. Factors were assessed via scree plots and eigenvalues. The EFA identified four main factors: insomnia, daytime sleepiness, substance use, and sleep-disordered breathing. The insomnia factor had 3 subfactors: psychological symptoms of insomnia, subjective description of insomnia, and insomnia due to periodic limb movements. The sleepiness factor had two subfactors: daytime sleepiness and neurological symptoms of narcolepsy. The novel substance use factor was homogeneous, as was the sleep-disordered breathing factor. Importantly, the EFA reassigned items from the original SDQ's NAR, PSY, and PLM subscales to five of the new subscales. The Sleep Apnea (SA) subscale emerged mostly unchanged. The 7 resulting factors comprised only 66 items of the original 176-item SDQ. These results have allowed the creation of a new shorter questionnaire, to be called the SDQ-2. External validation of the SDQ-2 is currently underway. It will likely prove to be a superior differential diagnostic instrument for sleep disorders clinics, compared to the original SDQ.

Dreamers' evaluation of the emotional valence of their day-to-day dreams is indicative of some mood regulation function.

Dreams may contribute to psychological adaptation by aiding in mood regulation. One way it could be achieved is through a desensitization process whereby negative events are replayed within the dream under lower conditions of negative emotionality. Evidence of this theory is supported by the tendency of dreamers to evaluate their emotions felt in their dreams more positively compared to an independent judge (i.e., positivity bias). Additionally, it has been observed that while dream emotions are typically more negative than pre-sleep emotions, morning emotions are more positive, suggesting that emotional regulation occurs overnight and may help improve mood in the morning. The present study aimed to examine the relationships between pre-sleep, dream, and morning mood and the potential desensitization function of remembered dreams as indicated by their effects on morning mood and stress. Methodology: Participants (N = 188; Mean age = 19.2, SD = 3.0) recorded their dreams (N = 345 dreams) and self-reported their stress and mood at bedtime, during their dream retrospectively, and upon waking. A judge also evaluated the subjects' dream moods. Subjects' positivity bias was defined as the difference between the subjects and the judge's evaluation of the positive emotions in the dream. Results: A MANOVA revealed that subjects perceived a higher level of positive emotions in their dreams compared to a judge. Multi-group path analysis revealed that some relationships between pre-sleep, dream, and morning emotions and stress differed in positive and negative dream nights. In both groups, the strongest predictors of morning mood and stress were pre-sleep mood and stress, respectively. The second strongest predictor of positive morning mood was the subjects' dream positivity bias. Conclusion: Results provide some support for the association of dreaming in mood regulation attributable to REM sleep. They also highlight that pathways implicated in mood regulation may be distinct from stress regulation.

Sleep architecture and emotional inhibition processing in adolescents hospitalized during a suicidal crisis.

Background: Suicide is the second leading cause of death in adolescents. Sleep disturbances could alter inhibitory processes and contribute to dangerous behaviors in this critical developmental period. Adolescents in suicidal crisis have been shown to have lighter sleep compared to healthy controls. Additionally, suicidal adolescents have lower neural resources mobilized by emotionally charged inhibition processing. The present exploratory study aimed to determine how sleep architecture in suicidal adolescents may relate to inhibition processing in response to emotional stimuli. Methods: Ten adolescents between 12 and 17 years of age with a diagnosis of major depressive disorder and who attempted suicide were recruited while hospitalized for a suicidal crisis in a psychiatric inpatient unit. Event-related potentials (ERPs) were recorded prior to bedtime during a Go/NoGo task involving pictures of sad, happy, and neutral faces. Polysomnography was then recorded throughout the night. Pearson correlations were conducted to investigate how inhibition performance and ERP parameters reflecting inhibition processing (i.e., P3d and N2d derived from difference waveform calculated as NoGo minus Go trials) relate to sleep architecture. Results: Poorer inhibition accuracy in response to emotional stimuli was significantly correlated with shorter REM sleep latency, higher REM sleep, and more frequent nocturnal awakenings. The P3d in response to sad faces was negatively correlated with NREM2 sleep and positively correlated with NREM3 sleep. No such association with the P3d was found for happy or neutral stimuli. There were no significant correlations for the N2d. Conclusion: Altered sleep in adolescents with depression who are in a suicidal crisisis associated with behavioral inhibition difficulties and fewer neural resources mobilized by inhibitory processes in emotionally charged contexts. This highlights the importance of addressing sleep disturbances while managing suicidal crises in adolescents.

Dissociated Effects of Age and Recent Troubling Experiences on Nightmares, Threats and Negative Emotions in Dreams.

Several studies have highlighted associations between adverse life events and the dysphoric character of dream experiences. This degree of continuity between waking-life and dream content seems partly attributed to the emotional and personal attachment linked to the incorporated waking experiences. Numerous changes in the processing of emotion-related stimuli are also reported across different human developmental stages. Therefore, we were interested in testing whether age would modulate the impact of recent troubling experiences on dream characteristics. Two hundred sixty participants, evenly distributed in five developmental stages, matched for gender and their exposure to a troubling experience, were selected from a large sample collected for a previous normative study of dreams of Canadians. Participants completed a dream questionnaire from which independent judges subsequently scored the dreams. We observed no interactions between the experience of troubling events and age. However, individuals who experienced a recent troubling event reported a higher frequency of nightmares and their dreams were more emotionally negative. Participants who experienced a moderately severe troubling event were also more likely to experience a dream whose maximal threat severity was of moderate intensity. Adolescents and young adults had dreams with a higher level of oneiric threats compared to older adults (>40 years old). Young adults also reported a higher frequency of nightmares compared to older adults. Our findings have implications for modern dream theories. They also suggest that dysphoric dreams might serve as potential proxies of mental health status and developmental stages. Future studies are now needed to explore the implications of these findings for psychological adaptation.

Psychiatric Admissions of Children and Adolescents Across School Periods and Daylight-Saving Transitions.

OBJECTIVES: This study sought to examine fluctuations in admissions to a child and adolescent inpatient psychiatry unit in relation to school breaks, school starts, as well as time change transitions in and out of Daylight-Saving Time (DST). METHODS: Five years (2012-2017) of youth inpatient admissions to a pediatric hospital in Ontario were retrieved (n=2,498). A sub-sample was grouped weekly, starting on the Sunday of each week for a total of 260 weekly time bins. The number of admissions during in and out of school periods, school starts in the fall and winter semester, and time change transitions were compared. RESULTS: Admissions were significantly higher during school periods as opposed to out of school periods, and significantly increased from prior- to post-school starts. No significant difference in admission rates were found in and out of DST changes. Weekly time series analyses for DST changes and monthly time series analyses for school starts did not identify a significant seasonality in admissions. CONCLUSIONS: These findings suggest that school periods and school onset may be significant stressors associated with an increased rate of psychiatric admissions. The presence of potential compensating factors is proposed to explain the lack of relationship between pedopsychiatric admissions and time change transitions.

OBJECTIFS: La présente étude visait à examiner les fluctuations des hospitalisations dans une unité psychiatrique pour enfants et adolescents relativement aux congés scolaires, aux retours en classe, ainsi qu'aux transitions à l'entrée et au sortir de l'heure d'été. MÉTHODES: Cinq ans (2012­2017) d'hospitalisations de jeunes patients dans un hôpital psychiatrique de l'Ontario ont été récupérés (n = 2 498). Un sous-échantillon a été assemblé chaque semaine, débutant le dimanche de chaque semaine pour un total de 260 plages horaires hebdomadaires. Le nombre d'hospitalisations durant les périodes scolaires et en dehors, les retours en classe à l'automne et au semestre d'hiver et les transitions du changement de temps a été comparé. RÉSULTATS: Les hospitalisations étaient significativement plus élevées durant les périodes scolaires par opposition aux périodes non scolaires, et augmentaient significativement d'avant le retour en classe à l'après retour en classe. Aucune différence significative des taux d'hospitalisation n'a été constatée à l'entrée ou à la sortie de l'heure d'été. Les analyses des séries de plages hebdomadaires pour les changements de l'heure d'été et les analyses des séries de temps mensuelles pour les retours en classe n'ont pas identifié de saisonnalité significative des hospitalisations. CONCLUSIONS: Ces résultats suggèrent que les périodes scolaires et le début de l'école peuvent être des stresseurs significatifs associés à un taux accru d'hospitalisations psychiatriques. La présence de facteurs de compensation potentiels est proposée pour expliquer l'absence de relation entre les hospitalisations pédopsychiatriques et les transitions du changement de l'heure d'été.

Sleep and Second-Language Acquisition Revisited: The Role of Sleep Spindles and Rapid Eye Movements.

INTRODUCTION: Second-language learning (SLL) depends on distinct functional-neuroanatomical systems including procedural and declarative long-term memory. Characteristic features of rapid eye movement (REM) and non-REM sleep such as rapid eye movements and sleep spindles are electrophysiological markers of cognitively complex procedural and declarative memory consolidation, respectively. In adults, grammatical learning depends at first on declarative memory ("early SLL") then shifts to procedural memory with experience ("late SLL"). However, it is unknown if the shift from declarative to procedural memory in early vs late SLL is supported by sleep. Here, we hypothesized that increases in sleep spindle characteristics would be associated with early SLL, whereas increases in REM activity (eg, density and EEG theta-band activity time-locked to rapid eye movements) would be associated with late SLL. METHODS: Eight Anglophone (English first language) participants completed four polysomnographic recordings throughout an intensive 6-week French immersion course. Sleep spindle data and electroencephalographic spectral power time-locked to rapid eye movements were extracted from parietal temporal electrodes. RESULTS: As predicted, improvements in French proficiency were associated with changes in spindles during early SLL. Furthermore, we observed increased event-related theta power time-locked to rapid eye movements during late SLL compared with early SLL. The increases in theta power were significantly correlated with improvements in French proficiency. DISCUSSION: This supports the notion that sleep spindles are involved in early SLL when grammar depends on declarative memory, whereas cortical theta activity time-locked to rapid eye movements is involved in late SLL when grammar depends on procedural memory.

Cannabinoids: Revealing their complexity and role in central networks of fear and anxiety.

The first aim of the present review is to provide an in-depth description of the cannabinoids and their known effects at various neuronal receptors. It reveals that cannabinoids are highly diverse, and recent work has highlighted that their effects on the central nervous system (CNS) are surprisingly more complex than previously recognized. Cannabinoid-sensitive receptors are widely distributed throughout the CNS where they act as primary modulators of neurotransmission. Secondly, we examine the role of cannabinoid receptors at key brain sites in the control of fear and anxiety. While our understanding of how cannabinoids specifically modulate these networks is mired by their complex interactions and diversity, a plausible framework(s) for their effects is proposed. Finally, we highlight some important knowledge gaps in our understanding of the mechanism(s) responsible for their effects on fear and anxiety in animal models and their use as therapeutic targets in humans. This is particularly important for our understanding of the phytocannabinoids used as novel clinical interventions.

Sleep problems and complexity of mental health needs in adolescent psychiatric inpatients.

Sleep problems are highly co-morbid with psychiatric disorders and are part of the complex and multiple factors contributing to symptoms and functional disability. The current study aimed to determine how sleep problems in the period preceding psychiatric admission relate to profiles of mental health needs in adolescent inpatients. This retrospective study included 424 adolescents (13-17 years) admitted over a five-year period to an acute crisis stabilization unit in a tertiary care pediatric hospital. Adolescents were divided into two age- and sex-matched groups based on the presence of moderate to severe sleep problems. Profiles of mental health needs were assessed at admission using the Child and Adolescent Needs and Strengths - Mental Health Acute (CANS-MH) and a complexity score was calculated as the total number of actionable CANS-MH items. Results showed a positive association between sleep problems and needs pertaining to eating disturbances, adjustment to trauma, and school attendance. Odds ratios for sleep problems increased progressively as the complexity scores increased, reaching a plateau at six needs beyond which odds ratios remained at their highest level. Adolescents with sleep problems were more likely to undergo medication changes during psychiatric hospitalization and were more likely to be discharged with antipsychotic medication. These findings suggest that sleep difficulties in adolescent inpatients may be associated with distinct and more complex profiles of mental health needs. The evaluation of sleep problems early in the course of psychiatric hospitalization may be an important part of the psychiatric assessment process to inform the global treatment plan.

Managing Insomnia Using Lucid Dreaming Training: A Pilot Study.

Objectives/Background: Despite Cognitive Behavioral Therapy for Insomnia (CBT-I) being considered the first-line treatment for insomnia, it is not without its challenges. As such it is worthwhile to consider, and test, alternative or adjuvant management options. Methods/Participants: The aim of the present study was to examine whether Lucid Dreaming Training for insomnia (LDT-I) impacted on insomnia, depressive and anxious symptomology in an open label trial of 48 adults with Insomnia Disorder. Participants completed the Insomnia Severity Index, General Anxiety Disorder-7 and Patient Health Questionnaire at baseline then one month following LDT-I. Training consisted of four modules delivered over a period of two consecutive weeks. Results: The results suggest, albeit preliminarily, that LDT-I may have a place within the non-pharmacological management of insomnia, as there were significant reductions in insomnia severity (t(46) = 8.16,p <.001), anxious symptomology (t(46) = 4.75,p <.001) and depressive symptomology (t(46) = 5.87,p <.001). Further, the effect size in terms of pre-post reductions on ISI scores was large (dz 1.17). Conclusions: Whilst the results are promising, further testing of LDT-I is needed to inform its place amongst the non-pharmacological treatments for insomnia.

Selective serotonin reuptake inhibitor use is associated with worse sleep-related breathing disturbances in individuals with depressive disorders and sleep complaints: a retrospective study.

STUDY OBJECTIVES: The effects of serotonergic agents on respiration neuromodulation may vary according to differences in the serotonin system, such as those linked to depression. This study investigated how sleep-related respiratory disturbances relate to depression and the use of medications commonly prescribed for depression. METHODS: Retrospective polysomnography was collated for all 363 individuals who met selection criteria out of 2,528 consecutive individuals referred to a specialized sleep clinic (Ottawa, Canada) between 2006 and 2016. The apnea-hypopnea index (AHI), oxygen saturation nadir, and oxygen desaturation index during REM and NREM sleep were analyzed using mixed analyses of covariance comparing 3 main groups: (1) medicated individuals with depressive disorders (antidepressant group; subdivided into the selective serotonin reuptake inhibitor and norepinephrine-dopamine reuptake inhibitor subgroups), (2) non-medicated individuals with depressive disorders (non-medicated group), and (3) mentally healthy control patients (control group). RESULTS: Individuals with depressive disorders (on antidepressants or not) had significantly higher AHIs compared to control patients (both P ≤ .007). The antidepressant group had a lower NREM sleep oxygen saturation nadir and a higher NREM sleep oxygen desaturation index than the control and non-medicated groups (all P ≤ .009). Within individuals with depressive disorders, independent of depression severity, the selective serotonin reuptake inhibitor group had a lower oxygen saturation nadir and a higher oxygen desaturation index during NREM sleep than the norepinephrine-dopamine reuptake inhibitor (both P ≤ .045) and non-medicated groups (both P < .001) and a higher NREM sleep AHI than the non-medicated group (P = .014). CONCLUSIONS: These findings suggest that the use of selective serotonin reuptake inhibitors may be associated with impaired breathing and worse nocturnal oxygen saturation in individuals with depressive disorders and sleep complaints, but this needs to be confirmed by prospective studies.

Using heart rate profiles during sleep as a biomarker of depression.

BACKGROUND: Abnormalities in heart rate during sleep linked to impaired neuro-cardiac modulation may provide new information about physiological sleep signatures of depression. This study assessed the validity of an algorithm using patterns of heart rate changes during sleep to discriminate between individuals with depression and healthy controls. METHODS: A heart rate profiling algorithm was modeled using machine-learning based on 1203 polysomnograms from individuals with depression referred to a sleep clinic for the assessment of sleep abnormalities, including insomnia, excessive daytime fatigue, and sleep-related breathing disturbances (n = 664) and mentally healthy controls (n = 529). The final algorithm was tested on a distinct sample (n = 174) to categorize each individual as depressed or not depressed. The resulting categorizations were compared to medical record diagnoses. RESULTS: The algorithm had an overall classification accuracy of 79.9% [sensitivity: 82.8, 95% CI (0.73-0.89), specificity: 77.0, 95% CI (0.67-0.85)]. The algorithm remained highly sensitive across subgroups stratified by age, sex, depression severity, comorbid psychiatric illness, cardiovascular disease, and smoking status. CONCLUSIONS: Sleep-derived heart rate patterns could act as an objective biomarker of depression, at least when it co-occurs with sleep disturbances, and may serve as a complimentary objective diagnostic tool. These findings highlight the extent to which some autonomic functions are impaired in individuals with depression, which warrants further investigation about potential underlying mechanisms.

Disentangling specific inhibitory versus general decision-making processes during sleep deprivation using a Go/NoGo ERP paradigm.

This study used a Go/NoGo ERP paradigm in which Go and NoGo stimuli occurred rarely and equally often in an attempt to determine if sleep deprivation has a general effect on decision-making or a more specific effect on inhibition. A Go/NoGo task was administered six times to eleven participants during 36 h of sleep deprivation and once again post recovery sleep. In the Go condition, the participant was asked to respond to the rare stimulus. In the separate NoGo condition, the participant was asked to withhold the response to the rare stimulus. ERPs were recorded to the rare stimuli. The NoGo P3 should be attenuated if sleep loss mainly affects inhibitory processes. Both Go and NoGo P3 should be attenuated if sleep loss affects general detection processes. During sleep loss, accuracy decreased for both tasks. RT also gradually increased for the Go task. Performance during the NoGo task was more complex and was better accounted by a speed-accuracy trade-off. Overall, findings indicate that sleep deprivation did not have specific effects on inhibition. However, the amplitude of the Go P3 occurred as early as 12 h after waking and might reflect an effect of task repetition rather than true sleep deprivation. In contrast, the NoGo P3 amplitude was not significantly reduced until after 24 and 36 h of wakefulness, suggesting a true sleep deprivation effect. Both Go and NoGo P3 post recovery sleep did not return to baseline levels, possibly due to residual sleep inertia.

Could long-term administration of melatonin to prepubertal children affect timing of puberty? A clinician's perspective.

Exogenous melatonin can be used to treat sleep disturbance in adults, children, and adolescents. While its short-term use is considered safe, there are some concerns that long-term use might delay children's sexual maturation, possibly by disrupting the decline in nocturnal melatonin levels that occur at the onset of puberty. This narrative review aimed to summarize some of the current knowledge about the potential effects of exogenous melatonin on puberty. We found no clinical studies that experimentally tested the effects of melatonin on pubertal timing in children, but we reviewed the small number of observational studies. We also drew on animal data to try to answer our question. The photoperiod and melatonin-mediated seasonal transitions in sexual activity and breeding in some mammals across the seasons have been used as a model of sexual development in mammals, including humans. The switch from non-sexual activity (in the non-breeding period) to sexual activity (in the breeding period) has been likened to the onset of puberty as there are similarities between the two. We conclude that to investigate an association between melatonin and pubertal timing, it will be important to conduct long-term randomized controlled trials of latency age children and also examine the cellular and systems-level interactions between melatonin and kisspeptin, a recently identified neuropeptide with a locus of action at the gonadotropin releasing hormone neurons that is important in contributing to the timing of puberty onset.

Sleep architecture in adolescents hospitalized during a suicidal crisis.

OBJECTIVE/BACKGROUND: Rates of suicide attempts in Canadian youths are concerning. Adolescence is a sensitive period for the emergence of both sleep and mood problems, two major risk factors for suicidality. This naturalistic study aimed to define the sleep profile of adolescents under the combined influence of suicidality, depression and pharmacotherapy during hospitalization for a suicidal crisis. PATIENTS/METHODS: Seventeen suicidal adolescents (15.0 + 1.2years, 82% females) with major depression were recruited from a Canadian pedopsychiatric inpatient unit. Seventeen non-depressed adolescents were retrospectively collated from another database (15.0 + 1.1years, 83% females). None of the participants had a history of sleep disorders or significant medical conditions. RESULTS: Compared to controls, suicidal adolescents had a longer sleep onset latency (Z = -4.5, p < 0.001), longer REM latency (Z = -3.2, p = 0.001), higher percentage of NREM1 sleep t(33) = -2.6, p = 0.020), and higher REM density (Z = -2.8, p = 0.004) than controls. Higher REM density correlated with higher CDI-II scores (r = 0.55, p = 0.27) A significant interaction indicated that the two groups had similar NREM3 percentages in the first two-thirds of the night, but that the suicidal group had significantly lower NREM3 percentage than the controls in the last third of the night (F(2,66) = 3.4, p = 0.041). CONCLUSIONS: Significant sleep abnormalities were observed during hospitalization for a suicidal crisis in a sample of depressed and mostly medicated adolescents. This included sleep initiation and REM sleep latency abnormalities, shallower sleep and high REM density. Future studies should decipher the relative effects of depression, suicidality and medication on sleep. These findings stress the need to address sleep disturbances in the management of suicidality in adolescents.

Sleep-related breathing disturbances in adolescents with treatment resistant depression.

OBJECTIVE/BACKGROUND: A considerable subgroup of adolescents does not respond to standard antidepressant treatments. There are some indications that sleep disordered breathing may contribute to refractory depression in adults, but little is known about how it may relate to the course of depressive disorders in adolescents. Focussing on a group of Canadian adolescents with treatment resistant depression (TRD), this study aimed to investigate how the severity of residual depressive symptoms following unsuccessful antidepressant trials relates to breathing disturbances during sleep. PATIENTS/METHODS: A retrospective chart review was conducted at a tertiary mental health facility. Polysomnography, the Beck Depression Inventory-II (BDI-II), and the Epworth Sleepiness Scale (ESS) were collated from 18 adolescents (15-18 years old, 44% females) patients with depressive disorders who did not respond to at least two 4-week trials of antidepressant medications. RESULTS: Of this sample, 39% reported at least mild levels of excessive daytime sleepiness, and 55% had an apnea/hypopnea index ≥1. Worse depressive symptoms correlated with higher RDI (r = 0.53, p = 0.022). This was mainly driven by respiratory effort-related arousals occurring during NREM sleep (r = 0.52, p = 0.029). No significant correlation was found between depressive symptoms and other respiratory or sleep variables. Higher daytime sleepiness correlated significantly with lower minimum oxygen desaturation (r = -0.51, p = 0.030). CONCLUSIONS: These results suggest that even subtle respiratory disturbances during sleep may play a role in persistent depressive symptoms and treatment resistance. Early screening for sleep-related breathing disturbances in adolescents with TRD may be relevant, since previous work suggests that treating sleep-related breathing disturbances can attenuate depressive symptoms.

A Novel Approach to Dream Content Analysis Reveals Links Between Learning-Related Dream Incorporation and Cognitive Abilities.

Can dreams reveal insight into our cognitive abilities and aptitudes (i.e., "human intelligence")? The relationship between dream production and trait-like cognitive abilities is the foundation of several long-standing theories on the neurocognitive and cognitive-psychological basis of dreaming. However, direct experimental evidence is sparse and remains contentious. On the other hand, recent research has provided compelling evidence demonstrating a link between dream content and new learning, suggesting that dreams reflect memory processing during sleep. It remains to be investigated whether the extent of learning-related dream incorporation (i.e., the semantic similarity between waking experiences and dream content) is related to inter-individual differences in cognitive abilities. The relationship between pre-post sleep memory performance improvements and learning-related dream incorporation was investigated (N = 24) to determine if this relationship could be explained by inter-individual differences in intellectual abilities (e.g., reasoning, short term memory (STM), and verbal abilities). The extent of dream incorporation using a novel and objective method of dream content analysis, employed a computational linguistic approach to measure the semantic relatedness between verbal reports describing the experience on a spatial (e.g., maze navigation) or a motor memory task (e.g., tennis simulator) with subsequent hypnagogic reverie dream reports and waking "daydream" reports, obtained during a daytime nap opportunity. Consistent with previous studies, the extent to which something new was learned was related (r = 0.47) to how richly these novel experiences were incorporated into the content of dreams. This was significant for early (the first 4 dream reports) but not late dreams (the last 4 dream reports). Notably, here, we show for the first time that the extent of this incorporation for early dreams was related (r = 0.41) to inter-individual differences in reasoning abilities. On the other hand, late dream incorporation was related (r = 0.46) to inter-individual differences in verbal abilities. There was no relationship between performance improvements and intellectual abilities, and thus, inter-individual differences in cognitive abilities did not mediate the relationship between performance improvements and dream incorporation; suggesting a direct relationship between reasoning abilities and dream incorporation. This study provides the first evidence that learning-related dream production is related to inter-individual differences in cognitive abilities.

Consolidative mechanisms of emotional processing in REM sleep and PTSD.

Research suggests sleep plays a role in the consolidation of recently acquired memories for long-term storage. rapid eye movement (REM) sleep has been shown to play a complex role in emotional-memory processing, and may be involved in subsequent waking-day emotional reactivity and amygdala responsivity. Interaction of the hippocampus and basolateral amygdala with the medial-prefrontal cortex is associated with sleep-dependent learning and emotional memory processing. REM is also implicated in post-traumatic stress disorder (PTSD), which is characterized by sleep disturbance, heightened reactivity to fearful stimuli, and nightmares. Many suffers of PTSD also exhibit dampened medial-prefrontal cortex activity. However, the effects of PTSD-related brain changes on REM-dependent consolidation or the notion of 'over-consolidation' (strengthening of memory traces to such a degree that they become resistant to extinction) have been minimally explored. Here, we posit that (in addition to sleep architecture changes) the memory functions of REM must also be altered in PTSD. We propose a model of REM-dependent consolidation of learned fear in PTSD and examine how PTSD-related brain changes might interact with fear learning. We argue that reduced efficacy of inhibitory medial-prefrontal pathways may lead to maladaptive processing of traumatic memories in the early stages of consolidation after trauma.

Autobiographical memory sources of threats in dreams.

Temporal sources of dream threats were examined through the paradigm of the Threat Simulation Theory. Two groups of young adults (18-24 years old), who did not experience severe threatening events in the year preceding their dream and reported a dream either with or without threats, were included. Participants (N = 119) kept a log of daily activities and a dream diary, indicating whether dream components referred to past experiences. The occurrence of oneiric threats correlated with the reporting of threats in the daily logs, their average severity, and the stress level experienced the day preceding the dream. The group whose dreams contained threats had significantly more references to temporal categories beyond one year than the group with dreams without threats. Our findings suggest that in the absence of recent highly negative emotional experiences, the threat simulation system selects memory traces of threatening events experienced in the past.

Novel Measures to Assess the Effects of Partial Sleep Deprivation on Sensory, Working, and Permanent Memory.

Sleepiness has repeatedly been demonstrated to affect performance on a variety of cognitive tasks. While the effects of total sleep deprivation (TSD) have been extensively studied, acute partial sleep deprivation (PSD), a more frequent form of sleep loss, has been studied much less often. The present study examined the effects of sleep deprivation on novel tasks involving classic sensory, working, and permanent memory systems. While the tasks did implicate different memory systems, they shared a need for effortful, sustained attention to maintain successful performance. Because of the novelty of the tasks, an initial study of the effects of TSD was carried out. The effects of PSD were subsequently examined in a second study, in which subjects were permitted only 4 h of sleep. A general detrimental effect of both total and PSD on accuracy of detection was observed and to a lesser extent, a slowing of the speed of responding on the different tasks. This overall effect is best explained by the often-reported inability to sustain attention following sleep loss. Specific effects on distinct cognitive processes were also observed, and these were more apparent following total than PSD.