Ray Norbury

Morningness is associated with several positive health outcomes and personality traits such as conscientiousness. In the current report, meta-analysis demonstrated a significant association between morningness and conscientiousness, data that are consistent with previous meta-analyses. Further, survey report and resting-state functional Magnetic Resonance Imaging (rs-fMRI, N = 43) indicated that the relationship between morningness and conscientiousness was moderated by functional connectivity with the Default Mode Network (DMN). DMN connectivity has been implicated in a number of cognitive functions and higher connectivity in this network is associated with higher conscientiousness.

Chronotype is a proxy for various intra-individual rhythms (e.g. sleep-wake cycles) which fluctuate throughout the day. The extent to which chronotype modulates cognitive performance remains unclear. Here, we systematically reviewed studies to determine the influence of chronotype on its own, and/or in interaction with time of day (ToD; optimal/non-optimal), in cognitive function in healthy adults. Following PRISMA guidelines, data searches were conducted in PubMed and Web of Science databases (11 March 2024), yielding 65 studies (53 in adults aged 18-45 y; 11 comparing adults aged 18-32 and 50-95 y; one involving only morning type adults aged 60-76 y). Most of the reviewed studies (>80%) indicated no main effect of chronotype on cognitive function. There was evidence from 29 (45.31%) of 64 studies involving adults aged 18-45 y of a synchrony effect (i.e. superior performance at optimal ToD) in morning and/or evening types, mostly in attention, inhibition, and memory. In older adults, there was evidence of a synchrony effect from 10 (83.33%) of 12 studies, especially on tasks involving fluid abilities. Limited evidence suggested higher activation of inhibition-related brain regions at optimal ToD in both chronotypes, and synchrony effects being impacted by certain exogenous factors known to affect arousal and performance (e.g. task complexity, lighting conditions). Our findings highlight the need to carefully consider age along with endogenous and exogenous sources of intra-individual variations in arousal while determining synchrony effect in cognitive functions. Not acknowledging these synchrony effects may also result in exaggerated cognitive deficits especially in the elderly.

Background: There is considerable evidence supporting the elevated risk of mental health problems in individuals with evening chronotype relative to those with morning or intermediate chronotypes. Recent data, however, suggest that this risk may be explained, at least partially, by poor sleep quality. Methods: This study aimed to further clarify the roles of chronotype and sleep quality in mental health outcomes (depression, anxiety, stress) in young individuals (18–40 years) living in the UK (n = 185) or Germany (n = 209). Results: Consistent with our recent observations in a comparable North Indian sample, we found that poor quality of sleep had significantly positive associations with adverse mental health outcomes both in the UK and Germany-based samples. Significant associations between evening chronotype and poor mental health were also evident, but these associations were fully mediated by poor quality of sleep in both samples. Conclusions: These observations suggest that efforts to identify sleep disruption in a timely manner and promotion of good sleep may prevent mental health problems, especially in individuals with evening chronotype and other known risks for mental disorders.

Previous behavioural data indicate lower word‐nonword recognition accuracy in association with a high level of positive schizotypy, psychopathy, or motor impulsivity traits, each with some unique contribution, in the general population. This study aimed to examine the neural underpinnings of these associations using functional magnetic resonance imaging (fMRI) in a volunteer sample. Twenty‐two healthy English‐speaking adults completed self‐report measures of schizotypy (Oxford‐Liverpool Inventory of Feelings and Experiences [O‐LIFE]), psychopathy (Triarchic Psychopathy Measure [TriPM]), and impulsivity (Barratt Impulsiveness Scale [BIS‐11]) and underwent whole‐brain fMRI while performing a lexical decision task (LDT) featuring high and low‐frequency words, real nonwords, and pseudohomophones. Higher positive schizotypy (Unusual Experiences) was associated with lower cerebellum activity during identification of low‐frequency words (over real nonwords). Higher Boldness (fearless dominance) and Meanness (callous aggression) facets of psychopathy were associated with lower striatal and posterior cingulate activity when identifying nonwords over words. Higher Motor Impulsivity was associated with lower activity in the fusiform (bilaterally), inferior frontal (right‐sided), and temporal gyri (bilaterally) across all stimuli‐types over resting baseline. Positive schizotypy, psychopathy, and impulsivity traits influence word‐nonword recognition through distinct neurocognitive mechanisms. Positive schizotypy and psychopathy appear to influence LDT performance through brain areas that play only a supportive (cerebellum) or indirect role in reading‐related skills. The negative association between Motor Impulsivity and activations typically found for phonological processing and automatic word identification indicates a reduced bilateral integration of the meaning and sound of mental word representations, and inability to select the appropriate outputs, in impulsive individuals.

Diurnal preference for evening time has been associated with poorer physical and mental health outcomes. In the current report, perceived loneliness and brain structure (hippocampal and amygdala volumes) were compared in a large (N = 4684) sample of morning- and evening-type individuals. Definite eveningness was associated with increased odds for reporting self-perceived loneliness and lonely evening-types had significantly smaller right hippocampal volume as compared to morning and more socially connected evening types. These data add to the mounting body of evidence linking an evening profile with increased risk for psychiatric disorder.

Eveningness, a preference for later sleep and rise times, has been associated with a number of negative outcomes in terms of both physical and mental health. A large body of evidence links eveningness to Major Depressive Disorder (MDD). However, to date, evidence quantifying this association is limited. The current meta-analysis included 43 effect sizes from a total 27,996 participants. Using a random-effects model it was demonstrated that eveningness is associated with a small effect size (Fisher’s Z = − 2.4, 95% CI [− 0.27. − 0.21], p < 0.001). Substantial heterogeneity between studies was observed, with meta-regression analyses demonstrating a significant effect of mean age on the association between diurnal preference and depression. There was also evidence of potential publication bias as assessed by visual inspection of funnel plots and Egger’s test. The association between diurnal preference and depression is small in magnitude and heterogenous. A better understanding of the mechanistic underpinnings linking diurnal preference to depression and suitably powered prospective studies that allow causal inference are required.

In the effort to limit the transmission of COVID-19, countries around the world have instigated extended periods of restricted movement that has significantly impacted work, leisure, and social interaction. An indirect outcome of these restrictions is increased loneliness and social isolation. Here, data from an online survey carried out in the latter part 2020/early 2021, demonstrated that evening-type is associated with increased odds of reporting self-perceived loneliness, but with no evidence for a similar association in neither-types. What future working and leisure patterns (the ‘new normal’) will look like is unclear. Nevertheless, the current data suggest eveningness should be a consideration in any interventions designed to reduce the impact of loneliness on physical and mental health.

A diurnal preference for eveningness is common in young adulthood and previous research has associated eveningness with anxiety symptoms as well as increased smoking and alcohol use behaviors. There is some evidence that impulsivity might be an important explanatory variable in these associations, but this has not been comprehensively researched. Here we used both subjective and objective measures of impulsivity to characterize impulsive tendencies in young adults and investigated whether trait impulsivity or trait anxiety could mediate the link between eveningness and substance use. A total of 191 university students (169 females), age range 18–25 y, completed the study. Diurnal preference, sleep quality, anxiety, impulsivity, and substance use were assessed by questionnaire. Impulsivity was also measured using a delay discounting task. Eveningness correlated with trait anxiety and trait impulsivity, and these associations were still significant after controlling for sleep quality. On the delayed discounting task, eveningness correlated with a tendency to prefer smaller immediate rewards over delayed, larger ones. Evening types also reported higher levels of alcohol and cigarette use even after controlling for sleep quality. These associations were found to be completely mediated by self-reported impulsivity; anxiety did not contribute. The current results could help inform interventions aiming to reduce substance use in young adult populations.

Eveningness (a diurnal preference for evening time) is associated with a number of negative health outcomes and risk and prevalence for psychiatric disorder. Our understanding of the anatomical substrates of diurnal preference, however, is limited. The current study used Voxel-Based Morphometry to compare grey matter volume in a large sample (N = 3730) of healthy adults determined by questionnaire to be either definite morning-type or definite evening-type. Eveningness was associated with increased grey matter volume in precuneus, brain regions implicated in risk and reward processing (bilateral nucleus accumbens, caudate, putamen and thalamus) and orbitofrontal cortex. These results indicate an anatomical-basis for diurnal preference which may underlie reported differences in behaviour and brain function observed in these individuals.