Temperament and character in primary insomnia

Personality and insomnia: A systematic review and narrative synthesis

The inherent nature of personality serves as a predisposing, and possible maintaining, factor of insomnia. However, methodological differences limit the ability to draw causal conclusions regarding the specific traits involved in the aetiology of the disorder. This systematic review of the relationship between insomnia and personality provides a narrative synthesis of the literature to date. Here, we identified N = 76 studies meeting the inclusion/exclusion criteria. The outcomes reliably evidenced the experience of insomnia to be associated with personality traits that are typically considered to be negative or maladaptive in nature. More specifically, insomnia was related to neuroticism, introversion, perfectionistic doubts and concerns, elevated personal standards, negative affect, social inhibition and avoidance, hysteria, hypochondriasis, psychasthenia, impulsive behaviour, anger, hostility, and psychopathic tendencies, schizotypal and borderline traits, reduced conscientiousness and self-directedness, and negatively perceived perception of the self. Several studies examined the role that personality plays in predicting the treatment efficacy and adherence of CBTi. Moving forward, longitudinal research, methodological consistency, the mediating role of treatment outcomes and adherence, and clinical and population representative samples should be prioritised. Methodological strengths and limitations of the literature are discussed alongside the next steps that should be taken to advance our understanding of the literature.

A Study of Factors Causing Sleep State Misperception in Patients with Depression

PURPOSE

Sleep state misperception, which is the discrepancy between subjective and objective sleep, is often observed in patients with depression. This phenomenon may delay the remission of depression. Previous studies have focused on the total sleep time (TST) misperception, with many of these studies using actigraphy. Thus, our study investigated depressed patients with the exploratory aim of clarifying factors associated with the sleep state misperception including the wake after sleep onset (WASO) misperception, with their objective sleep additionally evaluated by polysomnography (PSG).

PATIENTS AND METHODS

We conducted a cross-sectional study. Before undergoing overnight PSG monitoring, 40 patients with depression completed questionnaires that included the Beck Depression Inventory (BDI), Epworth sleepiness scale, Temperament and Character Inventory, and the Pittsburgh sleep quality index. Patients were also asked to estimate their subjective sleep duration after they woke up in the morning. Based on this data, we calculated the misperception using the following formula: subjective sleep duration minus objective sleep duration. We compared each factor between negative and positive misperception groups and the multiple regression analysis was performed for TST and WASO misperception, respectively.

RESULTS

Although sleep architectures, age, severity of depression and obstructive sleep apnea (OSA) exhibited differences in underestimating or overestimating the WASO, only sex differences were associated with underestimating or overestimating their total sleep time (TST). Moreover, BDI, the severity of OSA, sleep architectures (N1% and N2%), and benzodiazepine (BZD) use were significantly correlated with WASO misperception, whereas only OSA severity was significantly correlated with TST misperception. A subsequent multiple regression analysis demonstrated the BDI was independently correlated with the WASO misperception (β=0.341, p=0.049).

CONCLUSION

In clinical practice, interventions especially for OSA, and the reduction of depressive symptoms are an important method for improving patient sleep perception. Moreover, current results suggest that BZD prescriptions should be avoided as well.

Developmental pathways towards mood disorders in adult life: Is there a role for sleep disturbances?

INTRODUCTION

Mood disorders are among the most prevalent and serious mental disorders and rank high among to the leading global burdens of disease. The developmental psychopathology framework can offer a life course perspective on them thus providing a basis for early prevention and intervention. Sleep disturbances, are considered risk factors for mood disorders across childhood, adolescence and adulthood. Assuming that sleep disturbances may play a pivotal role in the pathogenesis of mood disorders from a life course point of view, we reviewed the data on developmental pathways towards mood disorders in adult life in relation to sleep disturbances.

METHOD

From February 2017, a systematic search was conducted in PubMed, PsycINFO and Embase electronic databases for literature on developmental pathways to mood disorders in adult life in relation to sleep disturbances and to 1) pre-natal stress, 2) early brain developmental processes, and 3) temperaments, character and attachment style.

RESULTS

Eleven, 54 and 15 articles were respectively selected.

CONCLUSIONS

Experimental and clinical studies revealed that exposure to prenatal/early life stress results in sleep disturbances such as poor sleep and altered circadian regulation phases and may predict or even precipitate mood disorders in adulthood. Chronic sleep disruption may interfere with neuronal plasticity, connectivity and the developing brain thus contributing to the development of mood disorders. In addition sleep and circadian dysregulations have been shown to be related to those temperaments, character and attachment styles which are considered precursors of mood disorders. Sleep and circadian behaviours may serve as early targets regarding mood disorders.

Adult insecure attachment plays a role in hyperarousal and emotion dysregulation in Insomnia Disorder

Studies show that unhelpful cognitive processes play a role in insomnia, whereas interpersonal factors have been less studied in insomnia. Attachment theory can be used as a cognitive-interpersonal framework for understanding insomnia. Because attachment insecurity (vs security) is related to psychiatric disorders the objective was to study the attachment style in insomnia. To this aim sixty-four subjects with Insomnia Disorder (DSM-5) and 38 good sleepers were evaluate in a cross-sectional study with: Attachment Style Questionnaire (ASQ), Arousal Predisposition Scale (APS), Pre-Sleep Arousal Scale (PSAS) and Difficulties in Emotion Regulation Scale (DERS). Differences in means between groups were assessed using t-test or Mann-Whitney U/Wilcoxon test. Linear/multiple regression analyses were performed. Subjects with insomnia (mean age 47.1 + 13 yrs) presented an insecure attachment style and higher scores in all the scales (ASQ, APS, PSAS, DERS p < 0.0001) than good sleepers (mean age 48.2 + 14 yrs). After taking into account anxiety/depressive symptoms, insecure attachment was related to hyperarousal trait (p = 0.02), pre-sleep hyperarousal (p = 0.04) and emotion dysregulation (p = 0.002). In conclusion subjects with insomnia showed an insecure attachment which was related to hyperarousal trait, pre-sleep hyperarousal and emotion dysregulation. It may intervene in the trajectory of insomnia starting from predisposition to perpetuation. Clinical implications are discussed.

Perfectionism and Polysomnography-Determined Markers of Poor Sleep

STUDY OBJECTIVES

Perfectionism has been suggested to represent a predisposing factor for poor sleep. However, previous studies have relied on self-reported measures. The association between perfectionism and poor sleep measured by polysomnography (PSG) warrants further investigation.

METHODS

The current retrospective exploratory study used the Frost Multidimensional Perfectionism Scale and PSG in an unselected sample of 334 consecutive sleep laboratory patients (140 males, 194 females, 44.6 ± 15.9 years). Data were analyzed using linear regression analyses.

RESULTS

High levels of perfectionism were associated with PSG-determined markers of poor sleep in the first sleep laboratory night. The total Frost Multidimensional Perfectionism Scale score was significantly associated with the number of nocturnal awakenings in the first sleep laboratory night. The subscales "concern over mistakes" and "personal standards" of perfectionism were significantly associated with markers of poor sleep. In contrast, there were only a few associations between perfectionism and PSG variables of the second sleep laboratory night.

CONCLUSIONS

This pattern of results suggests that high levels of perfectionism may predispose individuals to sleep disturbances in the context of acute stressors. Thus, the influence of perfectionism on poor sleep should be further investigated to improve treatment.

Insomnia heterogeneity: Characteristics to consider for data-driven multivariate subtyping

Meta-analyses and systematic reviews have reported surprisingly few consistent insomnia-characteristics with respect to cognitions, mood, traits, history of life events and family history. One interpretation of this limited consistency is that different subtypes of insomnia exist, each with its own specific multivariate profile of characteristics. Because previously unrecognized subtypes will be differentially represented in individual studies and dilute effect sizes of subtype-dependent characteristics of importance, they are unlikely to be reported consistently in individual studies, let alone in meta-analyses. This review therefore aims to complement meta-analyses by listing previously reported psychometric characteristics of insomnia, irrespective of the degree of consistency over studies. The review clearly indicates that characteristics of insomnia may not be limited to sleep. Reports suggest that at least some individuals with insomnia may deviate from people without sleep complaints with respect to demographics, mental and physical health, childhood trauma, life events, fatigue, sleepiness, hyperarousal, hyperactivity, other sleep disorders, lifetime sleep history, chronotype, depression, anxiety, mood, quality of life, personality, happiness, worry, rumination, self-consciousness, sensitivity, dysfunctional beliefs, self-conscious emotion regulation, coping, nocturnal mentation, wake resting-state mentation, physical activity, food intake, temperature perception and hedonic evaluation. The value of this list of characteristics is that 1) internet has now made it feasible to asses them all in a large sample of people suffering from insomnia, and 2) statistical methods like latent class analysis and community detection can utilize them for a truly bottom-up data-driven search for subtypes. The supplement to this review provides a blueprint of this multivariate approach as implemented in the Sleep registry platform (www.sleepregistry.nl), that allows for bottom-up subtyping and fosters cross-cultural comparison and worldwide collaboration on insomnia subtype finding - and beyond.

The ARSQ 2.0 reveals age and personality effects on mind-wandering experiences

The human brain frequently generates thoughts and feelings detached from environmental demands. Investigating the rich repertoire of these mind-wandering experiences is challenging, as it depends on introspection and mapping its content requires an unknown number of dimensions. We recently developed a retrospective self-report questionnaire-the Amsterdam Resting-State Questionnaire (ARSQ)-which quantifies mind wandering along seven dimensions: "Discontinuity of Mind," "Theory of Mind," "Self," "Planning," "Sleepiness," "Comfort," and "Somatic Awareness." Here, we show using confirmatory factor analysis that the ARSQ can be simplified by standardizing the number of items per factor and extending it to a 10-dimensional model, adding "Health Concern," "Visual Thought," and "Verbal Thought." We will refer to this extended ARSQ as the "ARSQ 2.0." Testing for effects of age and gender revealed no main effect for gender, yet a moderate and significant negative effect for age on the dimensions of "Self," "Planning," and "Visual Thought." Interestingly, we observed stable and significant test-retest correlations across measurement intervals of 3-32 months except for "Sleepiness" and "Health Concern." To investigate whether this stability could be related to personality traits, we correlated ARSQ scores to proxy measures of Cloninger's Temperament and Character Inventory, revealing multiple significant associations for the trait "Self-Directedness." Other traits correlated to specific ARSQ dimensions, e.g., a negative association between "Harm Avoidance" and "Comfort." Together, our results suggest that the ARSQ 2.0 is a promising instrument for quantitative studies on mind wandering and its relation to other psychological or physiological phenomena.

Case-control study on the association between qi-stagnation and insomnia

OBJECTIVE

To investigate the relationship between insomnia and qi-stagnation by using the international standardized measurement of sleep quality and the Traditional Chinese Medicine (TCM) Constitution Scales.

METHODS

A survey by means of the TCM Constitution Scales, the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and the Deep Sleep Scale (DSS) in 169 participants aged between 16 and 80 years old was conducted. Comparison was made to examine the sleep quality and insomnia symptoms in the qi-stagnation group and other-constitution group.

RESULTS

Univariate analysis found that the qi-stagnation group had a significantly increased risk of difficulty in falling asleep (OR=3.012, and 95% CI 1.310 to 6.923 for PSQI; OR=3.016, and 95% CI 1.358 to 6.709 for DSS) and early waking (OR=3.545, and 95% CI 1.229 to 10.232 for PSQI; OR=2.742, and 95% CI 1.072 to 7.014 for DSS), while the other-constitution group had a significant risk of dreaminess (OR=2.419, and 95% CI 1.154 to 5.072 for PSQI; OR=2.561, and 95% CI 1.116 to 5.880 for DSS). A dose-effect relationship existed between insomnia symptoms and qi-stagnation. Qi-stagnation significantly increased the risk of difficulty in falling asleep and early waking.

CONCLUSION

This case-control study revealed that there is a statistically significant association between qi-stagnation and insomnia. Based on this study, we recommend that further research should be conducted for the rehabilitative care and cure of insomnia from the perspective of TCM constitution.

The influence of personality and dysfunctional sleep-related cognitions on the severity of insomnia

Previous findings suggest that personality traits and dysfunctional sleep-related cognitions may perpetuate insomnia, but findings concerning this have been scarce. Thus, we hypothesized that personality and sleep-related cognitions influence the severity of insomnia, and investigated the association personality and sleep-related cognitions had with various sleep-related parameters, including severity of insomnia. Forty-four patients with psychophysiological insomnia were assessed using The Temperament and Character Inventory, the Insomnia Severity Index, the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale, the Dysfunctional Belief and Attitudes toward Sleep Scale, the Pre-Sleep Arousal Scale and the Hospital Anxiety and Depression Scale. Insomnia severity was significantly and positively correlated with harm avoidance, self-transcendence and sleep-related cognitions, and negatively correlated with novelty seeking, reward dependence, and cooperativeness. Dysfunctional sleep-related cognitions were positively correlated with insomnia severity and sleep quality. Stepwise multiple regression analysis showed that sleep-related cognitions, depression and reward dependence scores were significant determinants of insomnia severity, and that sleep-related cognitions and self-transcendence were significant positive determinants of sleep quality. Reward dependence, depression and sleep-related cognitions were associated with insomnia severity, and comparison with previous findings implied that 'internalizing behavior' and depression may be more plausible candidates for the link between personality and insomnia than anxiety. Considering the major role of cognitive-behavioral treatment (CBT) in the treatment of insomnia, assessment of these factors and management of sleep-related cognitions may help alleviate symptoms in patients with insomnia.

Biogenetic temperament and character in insomnia and depression

OBJECTIVE

We compared the biogenetic temperaments and characters of primary insomnia patients, major depressive disorder (MDD) patients with insomnia, MDD patients without insomnia, and normal controls.

METHODS

A total of 417 participants were recruited from a community and a psychiatric clinic in South Korea. Subjects were divided into 4 groups based on the Structured Clinical Interview for DSM-IV axis I disorder (SCID-IV) and sleep questionnaire: 1) normal controls (n=314), 2) primary insomnia (n=33), 3) MDD without insomnia (n=30), and 4) MDD with insomnia (n=40). All participants were requested to complete the Temperament and Character Inventory.

RESULTS

There were significant between-group differences in harm avoidance (HA)(F=32.96, p<0.001), reward dependence (RD)(F=5.21, p<0.01), self-directedness (SD)(F=24.72, p<0.001) and cooperativeness (CO)(F=15.75, p<0.001), after controlling for age and gender. Subjects with primary insomnia showed higher HA and lower SD than normal control, but lower HA and higher SD than MDD patients with insomnia. CO was lower in MDD patients, but not in subjects with primary insomnia. Lower RD was found only in MDD patients with insomnia.

CONCLUSION

The current study suggests that high HA and low SD were related to primary insomnia, although these patterns were more prominent in patients with MDD.

Risk factors for incident chronic insomnia: a general population prospective study

OBJECTIVE

The few population-based, prospective studies that have examined risk factors of incident insomnia were limited by small sample size, short follow-up, and lack of data on medical disorders or polysomnography. We prospectively examined the associations between demographics, behavioral factors, psychiatric and medical disorders, and polysomnography with incident chronic insomnia.

METHODS

From a random, general population sample of 1741 individuals of the adult Penn State Sleep Cohort, 1395 were followed-up after 7.5 years. Only subjects without chronic insomnia at baseline (n = 1246) were included in this study. Structured medical and psychiatric history, personality testing, and 8-h polysomnography were obtained at baseline. Structured sleep history was obtained at baseline and follow-up.

RESULTS

Incidence of chronic insomnia was 9.3%, with a higher incidence in women (12.9%) than in men (6.2%). Younger age (20-35 years), non-white ethnicity, and obesity increased the risk of chronic insomnia. Poor sleep and mental health were stronger predictors of incident chronic insomnia compared to physical health. Higher scores in MMPI-2, indicating maladaptive personality traits, and excessive use of coffee at baseline predicted incident chronic insomnia. Polysomnographic variables, such as short sleep duration or sleep apnea, did not predict incident chronic insomnia.

CONCLUSION

Mental health, poor sleep, and obesity, but not sleep apnea, are significant risk factors for incident chronic insomnia. Focusing on these more vulnerable groups and addressing the modifiable risk factors may help reduce the incident of chronic insomnia, a common and chronic sleep disorder associated with significant medical and psychiatric morbidity and mortality.

The impact of temperament and character on the efficacy of nonpharmacologic treatment of primary insomnia

Nonpharmacologic treatment, also known as cognitive behavioral treatment, is a first-line treatment of primary insomnia. We aimed to assess factors, including temperament and character, that were associated with responses to nonpharmacologic treatments of primary insomnia, that may assist physicians to recommend appropriate treatment. Outpatients diagnosed with psychophysiological insomnia (n = 99) were recruited between May 2009 and January 2010. Among 69 patients who consented to participate, 44 completed treatment and all assessment measures. In addition, 37 normal control subjects were also recruited. Baseline characteristics were assessed using the Temperament and Character Inventory, the Insomnia Severity Index, the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale, the Dysfunctional Beliefs and Attitudes about Sleep scale, and the Hospital Anxiety and Depression Scale. After treatment, all assessment scales excluding the Temperament and Character Inventory were repeated. All patients received nonpharmacologic treatments, including sleep restriction, cognitive therapy, and sleep hygiene education. Novelty seeking, harm avoidance, reward dependence, cooperativeness, and self-transcendence scores were significantly different between normal controls and study subjects. Participants were divided into treatment responders (n = 23) and nonresponders (n = 21). Responders were significantly younger (50.3 ± 12.8 vs 58.7 ± 9.6 years, P = .02) and had significantly higher reward dependence scores (51.7 ± 5.9 vs 42.9 ± 6.9, P < .01) compared with nonresponders. The difference in reward dependence scores remained significant after controlling for other factors (odds ratio, 1.23; 95% confidence interval, 1.08-1.40; P = .01). Among personality dimensions, reward dependence was significantly associated with response to nonpharmacologic treatment in patients with primary insomnia.

Sleep correlates of pervasive developmental disorders: a review of the literature

Sleep disturbance is a significant problem in the general pediatric population, and it occurs even more frequently in children with pervasive developmental disorders (PDDs). Much time and energy have been spent examining the characteristics that predispose children to insomnia and it is likely that equivalent factors influence sleep in PDDs. Though similarly affected, it is the unique set of characteristics incumbent in a diagnosis of PDD that has additive effects and increases the likelihood for developing other predisposing factors and subsequent sleep loss. This review summarized research that has explored the behavioral, cognitive, and emotional correlates of sleep disturbance in children with PDDs. The literature provided 38 sleep studies that used either subjective or objective sleep measures. Of these, 17 met criteria for inclusion. Studies were evaluated for their attempts at matching their study samples and adjusting for possible confounding variables. The results revealed that the combined effects of autism symptom severity, internalizing behavior, and externalizing behavior, were the main predisposing factors for the development of insomnia. Other factors included medical conditions, epilepsy, and medication use (likely a proxy for behavior difficulty and even sleep disorder). A bidirectional theoretical framework for sleep disturbance in children with PDDs has been posited as a conceptual guide for future study. Recommendations for future study designs are included.

Relationship between Personality and Insomnia in Panic Disorder Patients

OBJECTIVE

Panic disorder (PD) is frequently comorbid with insomnia, which could exacerbate panic symptoms and contribute to PD relapse. Research has suggested that characteristics are implicated in both PD and insomnia. However, there are no reports examining whether temperament and character affect insomnia in PD. Thus, we examined the relationship between insomnia and personality characteristics in PD patients.

METHODS

Participants were 101 patients, recruited from 6 university hospitals in Korea, who met the DSM-IV-TR criteria for PD. We assessed sleep outcomes using the sleep items of 17-item Hamilton Depression Rating Scale (HAMD-17)(item 4=onset latency, item 5=middle awakening, and item 6=early awakening) and used the Cloninger's Temperament and Character Inventory-Revised-Short to assess personality characteristics. To examine the relationship between personality and insomnia, we used analysis of variance with age, sex, and severity of depression (total HAMD scores minus sum of the three sleep items) as the covariates.

RESULTS

There were no statistical differences (p>0.1) in demographic and clinical data between patients with and without insomnia. Initial insomnia (delayed sleep onset) correlated to a high score on the temperamental dimension of novelty seeking 3 (NS3)(F(1,96)=6.93, p=0.03). There were no statistical differences (p>0.1) in NS3 between patients with and without middle or terminal insomnia.

CONCLUSION

The present study suggests that higher NS3 is related to the development of initial insomnia in PD and that temperament and character should be considered when assessing sleep problems in PD patients.

The effects of temperament and character on symptoms of depression in a chinese nonclinical population

Objective. To examine the relations between personality traits and syndromes of depression in a nonclinical Chinese population. Method. We recruited 469 nonclinical participants in China. They completed the Chinese version temperament and character inventory (TCI) and self-rating depression scale (SDS). A structural equation model was used to rate the relation between seven TCI scales and the three SDS subscale scores (based on Shafer's meta-analysis of the SDS items factor analyses). This was based on the assumption that the three depression subscales would be predicted by the temperament and character subscales, whereas the character subscales would be predicted by the temperament subscales. Results. The positive symptoms scores were predicted by low self-directedness (SD), cooperativeness (C), reward dependence (RD), and persistence (P) as well as older age. The negative symptoms scores were predicted only by an older age. The somatic symptoms scores were predicted by high SD. Conclusion. Syndromes of depression are differentially associated with temperament and character patterns. It was mainly the positive symptoms scores that were predicted by the TCI scores. The effects of harm avoidance (HA) on the positive symptoms scores could be mediated by low SD and C.

Premorbid personality in chronic fatigue syndrome as determined by the Temperament and Character Inventory

BACKGROUND

Using the Temperament and Character Inventory (TCI), we examined personality characteristics in patients with chronic fatigue syndrome (CFS) compared with healthy control subjects, and CFS patients with and without psychiatric diseases. There have been no previous reports assessing personality in CFS patients using the TCI.

METHODS

A total of 211 CFS patients and 90 control subjects completed the TCI and the Chalder Fatigue Scale questionnaires.

RESULTS

Compared with control subjects, CFS patients demonstrated significantly lower premorbid Novelty Seeking, and higher Harm Avoidance and persistence. The fatigue score for CFS patients with psychiatric diseases was higher than that for CFS patients without psychiatric diseases. Patients with CFS with psychiatric diseases showed lower premorbid Self-Directedness when compared with CFS patients without psychiatric diseases. The fatigue score was negatively correlated with premorbid Self-Directedness and Cooperativeness, and positively correlated with Harm Avoidance among CFS patients.

CONCLUSION

This study supported the stereotyped image of CFS patients as perfectionists, which is similar to the Persistence score, and neurotics, which is similar to the Harm Avoidance score. Patients displaying greater neuroticisms and poorer social and communication skills, similar to the Self-Directedness and Cooperativeness scores, tend to have intercurrent psychiatry diseases and show more severe symptoms of CFS.

The role of personality traits in insomnia

Insomnia is a highly prevalent sleep disorder, known to affect psychological well-being and quality of life. While perpetuating factors have received much attention, the role of predisposing factors has not been studied in much detail. The susceptibility to develop insomnia may be linked to the presence of certain personality features. Here, we review studies that assessed this particular aspect of insomnia. Due to various methodological issues, definitive conclusions cannot be drawn as of yet, and several conflicting findings remain. However, there is a common trend indicating that insomniacs display more signs of 'neuroticism', 'internalization', anxious concerns and traits associated with perfectionism. These factors may play varying roles depending on the specific subdiagnosis of insomnia. In addition, certain personality traits may be related to the response to (cognitive) behavioral treatment. For instance, insomniacs reporting less 'guardedness' and have a higher score on the MMPI 'hypomania' scale show less improvement through psychological treatment. The specific role of personality traits in the etiology of insomnia is not yet clear, because of a lack of longitudinal data. Personality factors may play a causal role in the development of insomnia, but may also be a consequence of the sleep problem and the associated daytime dysfunction. Future longitudinal studies should not view personality as a single predisposing factor, but assess it as a part of a larger group of interacting psychological and physiological factors involved in the predisposition to and perpetuation of chronic insomnia.

Restless Legs Syndrome and the five-factor model of personality: results from a community sample

OBJECTIVE

To examine personality characteristics as potential mediators of the association between Restless Legs Syndrome (RLS) and psychiatric disorders.

METHOD

Revised NEO Personality Inventory traits are compared in respondents with (n=42) versus without (n=982) a diagnosis of RLS in a general population sample.

RESULTS

RLS was associated with higher neuroticism after adjusting for potential confounders, including current psychopathology. Further analysis showed that the association between RLS and neuroticism contributes to, but does not fully explain, the relationship between RLS and either panic disorder or major depression.

CONCLUSIONS

Neuroticism may mediate part of the relationship between RLS and depression or panic, but the mechanisms of these associations need further exploration.

Sleep Beliefs Scale (SBS) and circadian typology

The aim of this work was to present the Sleep Beliefs Scale (SBS), a 20-item reviewed version of the Sleep Hygiene Awareness by Lacks and Rotert. We also examined for the first time the influence of circadian typology in sleep beliefs. Voluntary and unpaid psychology students participated in the study (n = 510; 182 men and 328 women), from Italy and Spain, aged between 18 and 33 (22.80 +/- 4.14 years). The mean score of SBS was 13.05 (SD = 3.46; range 2-20) in the total sample, with a distribution positive skewness to high score (correct beliefs) (Z = 1.82; P = 0.003). The internal consistency was good (Cronbach's alpha = 0.714) and factor analysis extracted three factors labelled 'Sleep-incompatible behaviours' (eight items), 'Sleep-wake cycle behaviours' (seven items) and 'Thoughts and attitudes to sleep' (five items). Circadian typology influences the total score and that of the three factors, as well the majority of the items that compose the SBS. The morning-type showed the best scores, the evening-type the worst, and the neither-type the medium scores. Moreover, in the men sample, the differences between circadian typology groups were higher than in the women sample. The SBS showed good psychometric properties; however, further studies in other countries, with clinical and non-student samples, and more aged subjects are needed so as to validate this psychometric instrument. The circadian typology is an individual difference that presented significant relationships with the sleep beliefs, the possibility of the evening-type being a risk factor for a worse sleep hygiene, and the maintenance of sleep problems such as insomnia may all be investigated in depth in future research.