The interaction between polygenic risk and environmental influences: A direct test of the 3P model of insomnia in adolescents.

BACKGROUND: Stress is a universal phenomenon and one of the most common precipitants of insomnia. However, not everyone develops insomnia after experiencing a stressful life event. This study aims to test aspects of Spielman's '3P model of insomnia' (during adolescence) by exploring the extent to which: (a) insomnia symptoms are predicted by polygenic scores (PGS); (b) life events predict insomnia symptoms; (c) the interaction between PGS and life events contribute to the prediction of insomnia symptoms; (d) gene-environment interaction effects remain after controlling for sex. METHODS: The sample comprised 4,629 twins aged 16 from the Twin Early Development Study who reported on their insomnia symptoms and life events. PGS for insomnia were calculated. In order to test the main hypothesis of this study (a significant interaction between PGS and negative life events), we fitted a series of mixed effect regressions. RESULTS: The best fit was provided by the model including sex, PGS for insomnia, negative life events, and their interactions (AIC = 26,158.7). Our results show that the association between insomnia symptoms and negative life events is stronger for those with a higher genetic risk for insomnia. CONCLUSIONS: This work sheds light on the complex relationship between genetic and environmental factors implicated for insomnia. This study has tested for the first time the interaction between genetic predisposition (PGS) for insomnia and environmental stressors (negative life events) in adolescents. This work represents a direct test of components of Spielman's 3P model for insomnia which is supported by our results.

Shorter night-time sleep duration and later sleep timing from infancy to adolescence.

BACKGROUND: Here, we (a) examined the trajectories of night-time sleep duration, bedtime and midpoint of night-time sleep (MPS) from infancy to adolescence, and (b) explored perinatal risk factors for persistent poor sleep health. METHODS: This study used data from 12,962 participants in the Avon Longitudinal Study of Parents and Children (ALSPAC). Parent or self-reported night-time sleep duration, bedtime and wake-up time were collected from questionnaires at 6, 18 and 30 months, and at 3.5, 4-5, 5-6, 6-7, 9, 11 and 15-16 years. Child's sex, birth weight, gestational age, health and temperament, together with mother's family adversity index (FAI), age at birth, prenatal socioeconomic status and postnatal anxiety and depression, were included as risk factors for persistent poor sleep health. Latent class growth analyses were applied first to detect trajectories of night-time sleep duration, bedtime and MPS, and we then applied logistic regressions for the longitudinal associations between risk factors and persistent poor sleep health domains. RESULTS: We obtained four trajectories for each of the three sleep domains. In particular, we identified a trajectory characterized by persistent shorter sleep, a trajectory of persistent later bedtime and a trajectory of persistent later MPS. Two risk factors were associated with the three poor sleep health domains: higher FAI with increased risk of persistent shorter sleep (OR = 1.20, 95% CI = 1.11-1.30, p < .001), persistent later bedtime (OR = 1.28, 95% CI = 1.19-1.39, p < .001) and persistent later MPS (OR = 1.30, 95% CI = 1.22-1.38, p < .001); and higher maternal socioeconomic status with reduced risk of persistent shorter sleep (OR = 0.99, 95% CI = 0.98-1.00, p = .048), persistent later bedtime (OR = 0.98, 95% CI = 0.97-0.99, p < .001) and persistent later MPS (OR = 0.99, 95% CI = 0.98-0.99, p < .001). CONCLUSIONS: We detected trajectories of persistent poor sleep health (i.e. shorter sleep duration, later bedtime and later MPS) from infancy to adolescence, and specific perinatal risk factors linked to persistent poor sleep health domains.

The role of inflammation in the prospective associations between early childhood sleep problems and ADHD at 10 years: findings from a UK birth cohort study.

BACKGROUND: Several underlying mechanisms potentially account for the link between sleep and attention deficit and hyperactivity disorder (ADHD), including inflammation. However, studies so far have been cross sectional. We investigate (a) the association between early childhood sleep and probable ADHD diagnosis in childhood and (b) whether childhood circulating inflammatory markers mediate these prospective associations. METHODS: Data from the Avon Longitudinal Study of Parents and Children were available for 7,658 10-year-old children. Parent-reported sleep duration, night awakening frequency and regular sleep routines were collected at 3.5 years. The Development and Wellbeing Assessment was administered to capture children with clinically relevant ADHD symptoms, or probable ADHD diagnosis. Blood samples were collected at 9 years, from which two inflammatory markers were obtained [interleukin-6 (IL-6) and C-reactive protein (CRP)]. Logistic regression analyses were applied to investigate the associations between sleep variables at 3.5 years and probable ADHD diagnosis at 10 years. Further, path analysis was applied to examine the potential mediating role of inflammation at 9 years (as measured by CRP and IL-6) in the associations between early sleep and ADHD at 10 years. RESULTS: Less regular sleep routines (OR = 0.51, 95% CI = 0.28-0.93, p = .029), shorter nighttime sleep (OR = 0.70, 95% CI = 0.56-0.89, p = .004) and higher night awakening frequency (OR = 1.27, 95% CI = 1.06-1.52, p = .009) at 3.5 years were associated with higher odds of ADHD at 10 years. Further, IL-6 at 9 years, but not CRP, mediated the association between irregular sleep routines and ADHD (bias-corrected estimate, -0.002; p = .005) and between night awakening and ADHD (bias-corrected estimate, 0.002; p = .003). CONCLUSIONS: Several sleep problems in early childhood constitute a risk factor for probable ADHD diagnosis at 10 years. Further, these associations are partially mediated by IL-6 at 9 years. These results open a new research vista to the pathophysiology of ADHD and highlight sleep and inflammation as potential preventative targets for ADHD.

Editorial: Therapies for mental health difficulties: finding the sweet spot between standardization and personalization.

There are strong arguments for standardizing therapies for mental health difficulties in young people and for the development of digital therapies. At the same time, the importance of personalized treatments is also increasingly apparent. In this editorial, we discuss challenges and the continued need to find the sweet spot between standardization and personalization when it comes to therapies for mental health difficulties. We illustrate our discussion with reference to insomnia in adolescents/young adults as well as the chronic health condition type 1 diabetes.

Sex differences in sleep quality and psychological distress: Insights from a middle-aged twin sample from Spain.

There is a moderate association between poor sleep and psychological distress. There are marked sex differences in the prevalence of both variables, with females outnumbering males. However, the origin of these sex differences remains unclear. The objectives of this study were to: (1) study genetic and environmental influences on the relationship between poor sleep quality and psychological distress; and (2) test possible sex differences in this relationship. The sample comprised 3544 participants from the Murcia Twin Registry. Univariate and multivariate twin models were fitted to estimate the magnitude of genetic and environmental influences on both individual variance and covariance between poor sleep quality and psychological distress. Sleep quality and psychological distress were measured using the Pittsburgh Sleep Quality Index and the EuroQol five-dimensions questionnaire, respectively. The results reveal a strong genetic association between poor sleep quality and psychological distress, which accounts for 44% (95%CI: 27%-61%) of the association between these two variables. Substantial genetic (rA = 0.50; 95%CI: 0.32, 0.67) and non-shared environmental (rE = 0.41; 95%CI: 0.30, 0.52) correlations were also found, indicating a moderate overlap between genetic (and non-shared environmental) factors influencing both phenotypes. Equating sexes in sex-limitation models did not result in significant decreases in model fit. Despite the remarkable sex differences in the prevalence of both poor sleep quality and psychological distress, there were no sex differences in the genetic and environmental influences on these variables. This suggests that genetic factors play a similar role for men and women in explaining individual differences in both phenotypes and their relationship.

The associations between paranormal beliefs and sleep variables.

Previous studies have found significant associations between paranormal beliefs and sleep variables. However, these have been conducted on a small scale and are limited in the number of sleep variables investigated. This study aims to fill a gap in the literature by investigating paranormal beliefs in relation to a wide range of sleep variables in a large sample. Participants (N = 8853) completed a survey initiated by the BBC Focus Magazine. They reported on their demographics, sleep disturbances and paranormal beliefs. Poorer subjective sleep quality (lower sleep efficiency, longer sleep latency, shorter sleep duration and increased insomnia symptoms) was associated with greater endorsement of belief in: (1) the soul living on after death; (2) the existence of ghosts; (3) demons; (4) an ability for some people to communicate with the dead; (5) near-death experiences are evidence for life after death; and (6) aliens have visited earth. In addition, episodes of exploding head syndrome and isolated sleep paralysis were associated with the belief that aliens have visited earth. Isolated sleep paralysis was also associated with the belief that near-death experiences are evidence for life after death. Findings obtained here indicate that there are associations between beliefs in the paranormal and various sleep variables. This information could potentially better equip us to support sleep via psychoeducation. Mechanisms underlying these associations are likely complex, and need to be further explored to fully understand why people sometimes report "things that go bump in the night".

Perspectives on interpersonal touch are related to subjective sleep quality.

Affective touch has been reported for its calming effects; however, it is less clear whether touch is associated with sleep. Here, the relationship between different touch variables and self-reported sleep indicators was investigated. Data were extracted from the Touch Test, a cross-sectional survey conducted in 2020. Data from a sample of 15,049 healthy adults from the UK (mean age = 56.13, SD = 13.8; 75.4% female) were analysed. Participants were asked to attribute positive, negative, or no effects on sleep to hugs, strokes, massages, intimate touch, and sleep onset with and without touch. The time since last intentional touch, touch amount satisfaction, and childhood bed routine with hugs and kisses were assessed. Sleep quality, duration, latency, wake after sleep onset and diurnal preference were measured. Data were analysed using chi-square tests and logistic regressions. Affective touch before sleep was perceived to have positive effects on sleep. Touch recency emerged as a significant predictor for some sleep variables, with a longer timespan since the last intentional touch relating to improved sleep quality, longer sleep duration, and shorter and fewer instances of waking up after sleep onset in some participants. Experiencing too much touch was related to lower sleep quality and higher instances of waking up after sleep onset. These findings highlight the importance of interpersonal touch for subjective sleep quality.

Sleep disturbances in ADHD: investigating the contribution of polygenic liability for ADHD and sleep-related phenotypes.

Sleep disturbances are common in attention deficit hyperactivity disorder (ADHD) and associated with poor outcomes. We tested whether, in children with ADHD, (1) polygenic liability for sleep phenotypes is over- or under-transmitted from parents, (2) this liability is linked to comorbid sleep disturbances, and (3) ADHD genetic risk is associated with comorbid sleep disturbances. We derived polygenic scores (PGS) for insomnia, chronotype, sleep duration, and ADHD, in 758 children (5-18 years old) diagnosed with ADHD and their parents. We conducted polygenic transmission disequilibrium tests for each sleep PGS in complete parent-offspring ADHD trios (N = 328) and an independent replication sample of ADHD trios (N = 844). Next, we tested whether insomnia, sleep duration, and ADHD PGS were associated with co-occurring sleep phenotypes (hypersomnia, insomnia, restless sleep, poor sleep quality, and nightmares) in children with ADHD. Children's insomnia and chronotype PGS did not differ from mid-parent average PGS but long sleep duration PGS were significantly over-transmitted to children with ADHD. This was supported by a combined analysis using the replication sample. Insomnia, sleep duration, and ADHD PGS were not associated with comorbid sleep disturbances. There is weak evidence that children with ADHD over-inherit polygenic liability for longer sleep duration and do not differentially inherit polygenic liability for insomnia or chronotype. There was insufficient evidence that childhood sleep disturbances were driven by polygenic liability for ADHD or sleep traits, suggesting that sleep disturbances in ADHD may be aetiologically different to general population sleep phenotypes and do not index greater ADHD genetic risk burden.

Aetiology of shame and its association with adolescent depression and anxiety: results from a prospective twin and sibling study.

BACKGROUND: Shame is considered a maladaptive self-conscious emotion that commonly co-occurs alongside depression and anxiety. Little is known, however, about the aetiology of shame and its associations with depression and anxiety. We estimated, for the first time, genetic and environmental influences on shame and on its associations with depression and anxiety in adolescence. METHODS: The sample was twin and sibling pairs from the Genesis 1219 Study (Time 1, N = 2,685; males 42.8%, Mage = 14.95, SD = 1.67, age range: 12-21; Time 2, N = 1618; males 39.7%, Mage = 16.97, SD = 1.64, age range: 14-23). Participants completed validated questionnaires to measure shame (at Time 1), depression and anxiety (at Times 1 and 2). RESULTS: Shame was moderately to strongly associated with concurrent depression and anxiety. Prospectively, shame was significantly associated with an increase in depression, but not anxiety. Genetic analyses revealed that shame was moderately heritable with substantial nonshared environmental influence. The associations between shame and concurrent depression and anxiety were primarily accounted for by overlapping genetic influences. Prospectively, the association between shame and later depression was primarily accounted for by genetic and nonshared environmental influences shared with earlier depression. The unique association between shame and later depression was mostly explained by common nonshared environmental influences. CONCLUSIONS: The findings offer novel evidence regarding aetiology of shame-although moderately heritable, shame in adolescents may also result from nonshared environmental factors. Genetic and nonshared environmental influences contribute to the co-occurrence of shame with depression and anxiety.

Sleep in adults from the UK during the first few months of the coronavirus outbreak.

The coronavirus disease 2019 (COVID-19) outbreak emerged at the end of 2019 and quickly spread around the world. Measures to counter COVID-19, including social distancing and lockdowns, created an unusual situation that had the potential to impact a variety of behaviours, including sleep, which is crucial for health and well-being. Data were obtained through an online survey. The total sample comprised 19,482 participants from the UK. Participants were asked several questions regarding sleep quality and quantity. Each participant completed the questionnaires once during a data collection period spanning January 20 to March 31, 2020. Data provided by different participants during different weeks (spanning time-periods just before COVID-19 was identified in the UK and during the early weeks following its arrival) were compared using analysis of variance tests and regressions. Regression analyses controlling for age, sex and ethnicity revealed significant associations of small magnitude between date of survey completion and sleep quality, sleep latency, number of awakenings and composite score of poor sleep quality. These analyses also indicated small increases in eveningness tendency as the study progressed. There was no change in sleep duration or time spent awake at night. The COVID-19 outbreak did not appear to impact negatively sleep in a substantial manner during the early stages in the UK. The small increases in sleep quality variables (except for time spent awake at night and sleep duration) and eveningness are nonetheless of interest. Further research is needed to understand how best to provide support to those most in need of a good night's sleep during this unprecedented time.

Associations between tactile intimacy and sleep quality in healthy adults: A systematic review.

Prior research suggests that different types of touch can affect sleep, but whether there is a consistent association between tactile intimacy and sleep quality is unclear. Here, we report a pre-registered systematic review (International Prospective Register of Systematic Reviews [PROSPERO], CRD42020158683) of studies examining the association between tactile intimacy and sleep quality in healthy adults. The databases PsycINFO, PubMed, Web of Science, the Cochrane Central Register of Controlled Trials and EMBASE were searched on August 7, 2020. A total of 13 studies met the inclusion criteria and were synthesised qualitatively. Most commonly, articles researched sexual intimacy in relation to sleep quality, but some studies also investigated non-sexual affective touch and emotionally neutral touch. Some evidence for a connection between sexual function, sexual satisfaction and masturbation with sleep quality was found; however, no evidence for an association between sexual frequency or sexual positions and sleep was found. Interestingly, studies employing more subjective approaches were more likely to report an association between touch and sleep, potentially highlighting a discrepancy between self-reported and the objectively measurable association between touch and sleep.

Association between symptoms of sleep apnea and problem behaviors in young adult twins and siblings.

BACKGROUND: Sleep apnea is one of the most common sleep disorders and it is related to multiple negative health consequences. Previous studies have shown that sleep apnea is influenced by genetic factors. However, studies have not investigated the genetic and environmental influences of symptoms of sleep apnea in young adults. Furthermore, the underpinnings of the relationship between apnea symptoms and internalizing/externalizing problems are unknown. The objectives of this study were to estimate the magnitude of: (1) genetic and environmental influences on self-reported apnea symptoms; (2) the relationship between self-reported apnea symptoms and internalizing/externalizing traits; (3) genetic and environmental influences on the associations between self-reported apnea symptoms, internalizing behaviors and externalizing behaviors. METHODS: In a twin/sibling study, univariate and multivariate models were fitted to estimate both individual variance and sources of covariance between symptoms of sleep apnea and internalizing/externalizing behaviors. RESULTS: Our results show that genetic influences account for 40% of the variance in sleep apnea symptoms. Moreover, there are modest associations between depression, anxiety and externalizing behaviors with apnea symptoms (ranging from r = 0.22-0.29). However, the origins of these associations differ. For example, whereas most of the covariation between symptoms of depression and sleep apnea can be explained by genes (95%), there was a larger role for the environment (53%) in the association between symptoms of anxiety and sleep apnea. CONCLUSIONS: Genetic factors explain a significant proportion of variance in symptoms of apnea and most of the covariance with depression.

What Do People Know About the Heritability of Sleep?

STUDY OBJECTIVES: Twin studies have provided data about the relative weight of genetic and environmental factors on sleep variables over the last few decades. However, heritability is a non-intuitive concept and it is often misunderstood even amongst the scientific community. This study aimed to analyze: (1) understanding of the meaning of heritability of insomnia; (2) the accuracy of estimations of heritability in the general population regarding three sleep traits (sleep duration, sleep quality and insomnia); (3) perceptions of the effectiveness of different treatments for insomnia depending on how the disorder is presented (i.e. having an environmental or genetic etiology) and whether the subject's estimate of genetic influence on sleep traits impacted beliefs about the effectiveness of different treatments. METHODS: Participants (N = 3658) completed a survey which included: questions about general genetic knowledge; a specific question about the meaning of heritability; estimates of heritability of three different sleep traits; and the effectiveness of different treatments for insomnia depending on how the etiology of this condition was presented. RESULTS: Fewer than 25% of the participants selected the correct description of the heritability of insomnia. Almost half of the sample incorrectly believed that heritability refers to the chance of passing a disorder onto their children. We also found that participants provided different estimates for the effectiveness of different treatments depending on the presumed etiology of the disorder. CONCLUSION: Most people do not have accurate knowledge about the concept of heritability. People's assumptions about the etiology of a disorder may influence which treatments they consider most effective.

The association between bullying-victimisation and sleep disturbances in adolescence: Evidence from a twin study.

Bullying-victimisation has been associated with sleep disturbances. This study investigated the degree to which subtypes of bullying-victimisation in adolescence are linked with sleep disturbances. Genetic and environmental contributions underlying bullying-victimisation and sleep disturbances were investigated. Participants (3,242-5,076 pairs) from a longitudinal community twin study reported on their bullying-victimisation at the age of 14 years, and sleep quality and insomnia symptoms at age 16. Regression analyses were used, accounting for the role of individual and family factors. Structural equation twin model fitting was conducted. Bullying-victimisation was modestly associated with sleep quality and insomnia symptoms (r = 0.22-0.23) and a similar strength of associations was found across bullying-victimisation subtypes (r = 0.11-0.22). Bullying-victimisation, sleep quality and insomnia symptoms were predominantly influenced by genes (25-59%) and non-shared environments (40-62%). The association between bullying-victimisation and sleep quality was explained by genetic and non-shared environmental influences. For insomnia symptoms and sleep quality, the association with bullying-victimisation was in part explained by a genetic overlap. Associations between bullying-victimisation and sleep disturbances are not limited to specific aspects of bullying-victimisation but appear to exist for all subtypes. These findings stimulate research questions regarding the mechanisms underlying these links. For example, could certain heritable traits, such as temperament, increase vulnerability to experiencing sleep disturbances and being bullied? Research on bullying and sleep should aim to take the role of genetic predisposition into account, while also noting that it is not the only causal influence. Understanding more about these pathways could strengthen the development of techniques to prevent these difficulties from occurring.

Is sleep the red flag to psychopathology's bull?

'Hippocrates flagged the value of sleep for good health' was the first line of the Annual Research Review (ARR) by Gregory and Sadeh (2016) in this journal, titled Sleep problems in childhood psychiatric disorders - a review of the latest science. Where Hippocrates has been referred to as the 'Father of Medicine', Professor Avi Sadeh has been respected as a 'Father of Paediatric Sleep Medicine' by those who had the privilege to meet him or read his science. Sadly, Avi Sadeh passed away in the same year this ARR was published. What he left behind was a legacy - including his predecessors (Professor Mary Carskadon), successors and those he inspired, who could be guided by the key findings from his 2016 ARR. These include (a) greater attention to the assessment of sleep in children; (b) sleep research on a wider range of psychiatric disorders; (c) a greater focus on and examination of mechanisms underlying associations; (d) a clearer consideration of developmental questions; and (e) large-scale well-designed treatment studies.

Editorial Perspective: Perils and promise for child and adolescent sleep and associated psychopathology during the COVID-19 pandemic.

It is anticipated that the novel coronavirus disease 2019 (COVID-19) pandemic and associated societal response will have wide-ranging impacts on youth development and mental health. Sleep is crucial for child and adolescent health and well-being, and the potential for sleep problems to emerge or worsen during and following the pandemic is high. This may be particularly true for children and adolescents who are at heightened risk for the onset of sleep and mental health disturbances and for those whom developmental changes impacting sleep are rapidly occurring. Youth with preexisting psychopathologies (including anxiety and depression) and neurodevelopmental conditions (including attention-deficit/hyperactivity disorder and autism spectrum disorder) could be especially vulnerable to disturbed sleep during this period of change and uncertainty. It is thus imperative that sleep considerations be part of research and clinical initiatives aimed at understanding and mitigating the impact of the COVID-19 pandemic in children and adolescents. This article considers ways in which the pandemic may impact sleep, including research and clinical implications.

Self-reported sleep patterns and quality amongst adolescents: cross-sectional and prospective associations with anxiety and depression.

BACKGROUND: Sleep problems are common in adolescence, and frequently comorbid with both anxiety and depression. Research studies have suggested a bidirectional relationship between sleep and psychopathology, which includes evidence that sleep interventions can alleviate symptoms of anxiety and depression. However, little is known about the nature of sleep problems amongst adolescents with anxiety and depression, and whether specific sleeping difficulties are involved in the longitudinal relationship between sleep, anxiety and depression. METHOD: The sample was derived from the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based, prospective, birth cohort study of children born in 1991-1992. Data were explored from a subset of participants who took part in a clinical assessment at age 15, on self-report sleep patterns and quality, and diagnostic outcomes of anxiety and depression (N = 5,033). Subsequent diagnostic and symptom severity data on anxiety and depression at ages 17, 21 and 24 were also examined. RESULTS: Cross-sectional and longitudinal analyses were conducted to explore the relationship between sleep problems, anxiety and depression. Results revealed that adolescents aged 15 with depression experience difficulties with both sleep patterns and sleep quality, whereas adolescents with anxiety only reported problems with sleep quality. A range of sleep variables at age 15 predicted the severity of anxiety and depression symptoms and the diagnoses of anxiety and depressive disorders at age 17, 21 and 24 years. CONCLUSIONS: The results provide further insight into the nature of sleep problems amongst adolescents with anxiety and depression, and the prospective relationship between sleep disturbance and future psychopathology. These data suggest that targeting sleep difficulties during adolescence may have long-term mental health benefits.

Dysfunctional beliefs about sleep and insomnia symptoms in early adulthood: A twin and sibling study.

This study examines the associations between dysfunctional belief about sleep (DBAS), its subtypes and insomnia symptoms and estimates the relative contribution of genetic and environmental influences to these variables and the associations between them. The data came from G1219, a twin/sibling study that comprises 862 individuals (aged 22-32 years, 34% male). The Insomnia Symptoms Questionnaire was used to measure insomnia symptoms and a 10-item version of the Dysfunctional Beliefs and Attitudes about Sleep Scale was used to assess DBAS. A higher DBAS score was associated with more insomnia symptoms. Overall DBAS showed a mainly non-shared environmental influence (86%). The genetic correlation between overall DBAS and insomnia symptoms was large but not significant, the shared environmental correlation was very small, negative and not significant, whereas a moderate, significant overlap in the non-shared environmental influences was evident (non-shared environmental correlation = 0.32). For the association between the subscales of DBAS and insomnia symptoms no significant overlap for genetic (weak to strong associations) or shared environmental factors (very weak negative to strong associations) was indicated. Most of the non-shared environmental influences on the four variables were significantly moderately correlated (non-shared environmental correlation = 0.24-0.46). These findings help to deepen our understanding of cognitive theories of insomnia by dissecting one of its crucial elements and illuminating the factors involved in its association with insomnia symptoms.

Subjective sleep-related variables in those who have and have not experienced sleep paralysis.

Research suggests that poor sleep quality is related to the occurrence of sleep paralysis, although the precise relationship between these two variables is unknown. This association has generated interest due to the related possibility that improving sleep quality could help to combat episodes of sleep paralysis. To date, studies examining the association between sleep quality and sleep paralysis have typically measured sleep quality using general measures such as the global score of the Pittsburgh Sleep Quality Index (PSQI). The aim of this study was to increase the precision of our understanding of the relationship between sleep paralysis and other aspects of sleep by investigating associations between different sleep-related variables and sleep paralysis. Using data from the G1219 twin/sibling study, analyses were performed on 860 individuals aged 22-32 years (66% female). Results showed that two components of the PSQI, sleep latency and daytime dysfunction, were predictors of sleep paralysis. In addition, a number of other sleep-related variables were related significantly to sleep paralysis. These were: insomnia symptoms, sleep problems commonly related to traumatic experiences, presleep arousal, cognitions about sleep and excessive daytime sleepiness. There was no relationship with sleep-disordered breathing, diurnal preference or sleeping arrangements. Potential mechanisms underlying these results and suggestions for future research are discussed.