Winter Depression: Integrating mood, circadian rhythms, and the sleep/wake and light/dark cycles into a bio-psycho-social-environmental model

Melatonin immunoreactivity of epidermal skin is higher in the evening than morning but does not account for erythema sensitivity

The skin is a site of melatonin synthesis, and melatonin has a role in protecting against ultraviolet radiation-induced damage. Ultraviolet B (UVB) induced erythema seems to vary between morning and evening. We investigated whether epidermal melatonin immunoreactivities in the morning differed from those in the evening, and whether UVB-induced erythema was associated with these melatonin immunoreactivities in healthy volunteers. Erythema sensitivity of the skin was determined in the morning and in the evening by scoring the Minimal Erythema Dose and quantifying the erythema index (EI). We took biopsies from the non-UVB-exposed skin of healthy volunteers (n = 39) in the morning and in the evening to study melatonin immunoreactivity with immunohistochemistry (IHC). In the IHC staining, there was more melatonin immunoreactivity in the evening than in the morning (p < .001). Erythema was more pronounced in the evening than in the morning irradiated skin (p < .001). The graded amount of melatonin immunoreactivity in the samples was not associated with the EI. We discovered melatonin immunoreactivity of the non-irradiated skin to vary diurnally. However, endogenous skin melatonin does not seem to be the reason why NB-UVB induces more erythema in the evening than in the morning.

Sleep and circadian rhythm profiles in seasonal depression

Sleep and circadian rhythm disruptions are symptoms of, and hypothesized underlying mechanisms in, seasonal depression. Discrepant observational findings and mixed responses to sleep/circadian-based treatments suggest heterogenous sleep and circadian disruptions in seasonal depression, despite these disruptions historically conceptualized as delayed circadian phase and hypersomnia. This study used a data-driven cluster analysis to characterize sleep/circadian profiles in seasonal depression to identify treatment targets for future interventions. Biobehavioral measures of sleep and circadian rhythms were assessed during the winter in individuals with Seasonal Affective Disorder (SAD), subsyndromal-SAD (S-SAD), or nonseasonal, never depressed controls (total sample N = 103). The following variables were used in the cluster analysis: circadian phase (from dim light melatonin onset), midsleep timing, total sleep time, sleep efficiency, regularity of midsleep timing, and nap duration (all from wrist actigraphy). Sleep and circadian variables were compared across clusters and controls. Despite limited sleep/circadian differences between diagnostic groups, there were two reliable (Jaccard Coefficients >0.75) sleep/circadian profiles in SAD/S-SAD individuals: a 'Disrupted sleep' cluster, characterized by irregular and fragmented sleep and an 'Advanced' cluster, characterized by early sleep and circadian timing and longer total sleep times (>7.5 h). Clusters did not differ by depression severity. Midsleep correlated with DLMO (r = 0.56), irregularity (r = 0.3), and total sleep time (r = -0.27). Sleep and circadian disruptions in seasonal depression are not uniformly characterized by hypersomnia and circadian phase delay. Presence of distinct sleep and circadian subgroups in seasonal depression may predict successful treatment response. Prospective assessment and tailoring of individual sleep and circadian disruptions may reduce treatment failures.

Melatonin In Acute Mania Investigation (MIAMI-UK). A randomized controlled trial of add-on melatonin in bipolar disorder

OBJECTIVES

Current options for treating emergent episodes of hypomania and mania in bipolar disorder are limited. Our objective was to compare the effectiveness and safety of add-on melatonin in hypomania or mania over 3 weeks as a well-tolerated therapy.

METHODS

A randomized, double-blind, parallel-group, 3-week comparison of modified release melatonin (n = 21) vs placebo (n = 20) in adult bipolar patients aged 18-65 years. Permuted block randomization was used with participants and investigators masked to treatment allocation. Trial registration is ISRCTN28988273 and EUdraCT2008-000281-23. Approved by the South Central National Research Ethics Service (Oxford REC A) ref: 09/H0604/63.

RESULTS

The trial was negative as there was no significant difference between melatonin and placebo on the primary outcome-mean Young Mania Rating Scale (YMRS) score at Day 21: (mean difference [MD] -1.77 ([95% CI: -6.39 to 2.85]; P = .447). Significantly fewer patients on melatonin scored 10 or more on the Altman Self Rating Mania Scale: (odds ratio [OR] 0.164 [95% CI: 0.0260-1.0002]; P = .05). Quick Inventory of Depression Symptomatology Clinician Version-16 (QIDS-C16) scores were not significantly different. (OR 1.77 [95% CI: 0.43-7.29]; P = .430). The proportion of patients scoring less than or equal to 5 on the self-report QIDS-SR16 at end-point was greater for the melatonin group (OR 8.35 [95% CI: 1.04-67.23]; P = .046).

CONCLUSIONS

In this small trial, melatonin did not effectively treat emerging hypomania or mania as there was no significant difference on the primary outcome. The sample size limitation and secondary outcomes suggest further investigation of melatonin treatment in mood episodes is indicated.

Chronobiologic parameter changes in patients with major depressive disorder and sleep disturbance treated with adjunctive brexpiprazole: An open-label, flexible-dose, exploratory substudy

BACKGROUND

Circadian rhythm disturbances have been reported in patients with major depressive disorder (MDD). Among these is an increased phase angle between peak cortisol concentration and dim-light melatonin onset (DLMO). The aim of this study was to evaluate changes in chronobiologic parameters of sleep in patients with MDD receiving adjunctive brexpiprazole.

METHODS

This was an interventional, multicenter, open-label, flexible-dose, exploratory study in patients with MDD and inadequate response to antidepressant treatment who were experiencing sleep disturbances. Patients received adjunctive brexpiprazole 2-3 mg/day for 8 weeks. Outcome measures included cortisol and melatonin levels, used to calculate phase angle, and the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN).

RESULTS

The mean (standard error) phase angle between peak cortisol and DLMO increased by 108 (61) minutes from baseline to Week 8 (n = 9). BRIAN Total score changed (improved) by -14.6 (4.6) points from baseline to Week 8 (n = 9). Change in phase angle and BRIAN Total score showed a moderate-to-high correlation (Pearson coefficient: 0.68; 95% confidence limits: 0.04, 0.93; p = 0.040).

LIMITATIONS

This study is limited by its small sample size, and its single-arm, open-label design.

CONCLUSIONS

The findings provide a preliminary indication that the phase angle between peak cortisol and DLMO is of interest as a potential biomarker for depression and therapeutic response. Adjunctive brexpiprazole may represent a strategy for correcting circadian dysfunction in patients with MDD and inadequate response to antidepressant treatment. ClinicalTrials.gov identifier: NCT01942733.

Efficacy of light therapy for a college student sample with non-seasonal subthreshold depression: An RCT study

BACKGROUND

Light therapy has been successfully used to treat seasonal and non-seasonal depression, but there is limited evidence for its efficacy in subthreshold depression. This study examines the efficacy of light therapy for symptoms of depression and anxiety in non-seasonal subthreshold depression.

METHODS

College students with non-seasonal subthreshold depression were recruited. The participants were randomly allocated to one of the three conditions: high- (LT-5000 lux) and low-intensity (LT-500 lux) light therapy conditions and a waiting-list control condition (WLC). The primary outcome was Hamilton Depression Rating Scale (HAMD), and secondary outcomes were Beck Depression Inventory-II (BDI-II) and state anxiety inventory (SAI), which were assessed at baseline (Week 0), during the trial (Week 4), and after completion of the light therapy (Week 8).

RESULTS

A total of 142 participants completed the trial. The LT-5000 (effect size [d] = 1.56, 95% CI: 1.15 to 1.98) and LT-500 conditions (d = 0.84, 95% CI: 0.43 to 1.26) were significantly superior to the WLC condition. For the LT-5000, LT-500, and WLC conditions by the end of the 8-week trial, a response on the HAMD was achieved by 70.0%, 42.0% and 19.0% of the participants, and remission was achieved by 76.0%, 54.0%, and 19.0%, respectively.

LIMITATIONS

The subjects were not followed up regularly after completion of the trial.

CONCLUSION

Light therapy, both at high- and low-intensity, was efficacious in the treatment of college students with non-seasonal subthreshold depression. High-intensity light therapy was superior to low-intensity light therapy by the end of an 8-week trial.

Can we prevent seasonal affective disorder (SAD) with melatonergic agents?

Seasonal affective disorder (SAD) is a recurrent form of major depression, particularly occurring in the winter months with a generally spontaneous remission in spring/summer. The predictable nature of this condition provides a potentially unique opportunity to prevent recurrence in sufferers of SAD. The Cochrane Review discussed here examines the evidence for melatonin and agomelatine in preventing SAD, putting its findings into their clinical context.

Evaluation of QT Liability for PF-05251749 in the Presence of Potential Circadian Rhythm Modification

PF-05251749 is a dual inhibitor of casein kinase 1 δ/ε, key regulators of circadian rhythm. As a result of its mechanism of action, PF-05251749 may also change the heart rate corrected QT (QTc) circadian rhythm, which may confound detection of drug-induced QTc prolongation. In this analysis, a nonlinear mixed effect model including a multioscillator function was developed in addition to fitting the prespecified linear mixed effect concentration-QTc model, to identify QTc liability of PF-05251749 in the presence of potential circadian rhythm change. The modeling results suggested lack of clinically meaningful QTc prolongation (upper bound of 90% confidence interval for ∆∆QTc < 10 milliseconds) and that the drug-induced QTc circadian rhythm change was not present. However, simulation results indicated that inference of drug-induced QTc prolongation could be misleading if the drug effect on QTc circadian rhythm is not properly addressed. The modeling and simulation results suggest that prespecification of the concentration-QTc model should be reconsidered for drugs with circadian rhythm modulation potential.

Characteristics of Mild Cognitive Impairment in Northern Japanese Community-Dwellers from the ORANGE Registry

A gradually increasing prevalence of mild cognitive impairment (MCI) is recognized in the super-aging society that Japan faces, and early detection and intervention in community-dwellers with MCI are critical issues to prevent dementia. Although many previous studies have revealed MCI/non-MCI differences in older individuals, information on the prevalence and characteristics of MCI in rural older adults is limited. The aim of this study was to investigate differential characteristics between older adults with and without MCI. The investigation was conducted over one year from 2018 to 2019. Participants were recruited from Akita in northern Japan. Neuropsychological assessments were applied to classify MCI, including the National Center for Geriatrics and Gerontology Functional Assessment Tool (NCGG-FAT) and the Touch panel-type Dementia Assessment Scale (TDAS) based on the Alzheimer's disease assessment scale. Our samples consisted of 103 older adults divided into 54 non-MCI and 49 MCI. The MCI group had lower scores of all cognitive items. Our results showed that individuals with MCI had significantly slower walking speed (WS) and worse geriatric depression scale (GDS) compared to non-MCI. In addition, WS was significantly associated with some cognitive items in non-MCI, but not in MCI. Finally, we showed that predictive variables of MCI were WS and GDS. Our study provides important information about MCI in rural community-dwellers. We suggest that older adults living in a super-aging society should receive lower limb training, and avoiding depression in older adults through interaction of community-dwellers may contribute to preventing the onset of MCI.

Sleep in seasonal affective disorder

Sleep in seasonal affective disorder (SAD) has been primarily characterized by delayed sleep timing and self-reports of hypersomnolence. It is unclear whether delayed sleep timing is due to circadian or behavioral misalignment and if effective treatments operate independently of the circadian system. Discrepancies between self-report and actigraphic/polysomnographic sleep duration in SAD hinder clarification of hypersomnolence as a cardinal symptom. Previous studies have largely neglected the summer remission period in SAD, which could yield valuable insight to the role sleep disturbances play in the onset and recurrence of winter depressive episodes. Future studies should incorporate multi-method, multi-season assessment of sleep and circadian rhythms to best characterize relevant sleep-circadian phenotypes. Empirically determining sleep phenotypes present in SAD will pave the way for targeted sleep interventions.

Advanced melatonin onset relative to sleep in women with unmedicated major depressive disorder

Studies on circadian timing in depression have produced variable results, with some investigations suggesting phase advances and others phase delays. This variability may be attributable to differences in participant diagnosis, medication use, and methodology between studies. This study examined circadian timing in a sample of unmedicated women with and without unipolar major depressive disorder. Participants were aged 18-28 years, had no comorbid medical conditions, and were not taking medications. Eight women were experiencing a major depressive episode, nine had previously experienced an episode, and 31 were control participants with no history of mental illness. Following at least one week of actigraphic sleep monitoring, timing of salivary dim light melatonin onset (DLMO) was assessed in light of <1 lux. In currently depressed participants, melatonin onset occurred significantly earlier relative to sleep than in controls, with a large effect size. Earlier melatonin onset relative to sleep was also correlated with poorer mood for all participants. Our results indicate that during a unipolar major depressive episode, endogenous circadian phase is advanced relative to sleep time. This is consistent with the early-morning awakenings often seen in depression. Circadian misalignment may represent a precipitating or perpetuating factor that could be targeted for personalized treatment of major depression.

Depressive mood and circadian rhythms disturbances as outcomes of seasonal affective disorder treatment: A systematic review

BACKGROUND

The present systematic review was aimed at critically summarizing the evidence about interventions focused on circadian rhythms and mood symptoms in seasonal affective disorder (SAD).

METHODS

A systematic search of the electronic databases PUBMED, PsycINFO and Web of Science was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Original papers reporting data about the effects of treatments on both mood and circadian rhythms disturbances in SAD patients were considered for inclusion. The quality of the evidence provided by the eligible studies was assessed using the Revised Cochrane Risk of Bias Tool (RoB 2.0) and the Cochrane Risk of Bias in Non-Randomized Studies of Interventions Tool (ROBINS-I).

RESULTS

Forty papers were deemed eligible for the systematic review. The evidence of treatment outcomes referring to circadian disturbances was not robust. Despite this, bright light therapy (BLT) demonstrates to phase-advance delayed rhythms and to improve sleep-wake disorders. As for mood symptoms, both BLT and selective serotonin reuptake inhibitors (SSRIs) show evidence of efficacy. The possible connection between improvements of mood symptoms and changes in circadian outcomes seems controversial.

LIMITATIONS

The included studies presented considerable methodological heterogeneity, small sample sizes and non-optimal sample selection.

CONCLUSIONS

The effectiveness of BLT in depressive symptoms and circadian disturbances of SAD was outlined by the present systematic review. The evidence about other biological and pharmacological treatments, although promising, should be replicated. A multifactorial etiopathogenesis could explain the heterogeneous clinical presentations of SAD and the complex link between mood and circadian symptoms.

Heterogeneity of sleep quality in relation to circadian preferences and depressive symptomatology among major depressive patients

BACKGROUND

The current study aimed at investigating the latent dimensional structure of sleep quality as indexed by the seven components of the Pittsburgh Sleep Quality Index (PSQI), as well as latent covariance structure between sleep quality, circadian preferences and depressive symptoms.

METHODS

Two hundred twenty-five patients with major depressive disorder (MDD), with an average age of 29.92 ± 10.49 years (aged between 17 and 63), participated in the study. The PSQI, Morningness-Eveningness Questionnaire (MEQ) and Beck Depression Inventory (BDI) were administered to participants. Four sets of latent class analyses were subsequently run to obtain optimal number of latent classes best fit to the data.

RESULTS

Mixture models revealed that sleep quality is multifaceted in MDD. The data best fit to four-latent-class model: Poor Habitual Sleep Quality (PHSQ), Poor Subjective Sleep Quality (PSSQ), Intermediate Sleep Quality (ISQ), and Good Sleep Quality (GSQ). MDD patients classified into GSQ latent class (23.6%) reported the lowest depressive symptoms and were more prone to morningness diurnal preferences compared to other three homogenous sub-groups. Finally, the significant association between eveningness diurnal preferences and depressive symptomatology was significantly mediated by poor sleep quality.

LIMITATION

The cross-sectional nature of the study and the lack of an objective measurement of sleep such as polysomnography recordings was the most striking limitation of the study.

CONCLUSIONS

We concluded sleep quality in relation to circadian preferences and depressive symptoms has a heterogeneous nature in MDD.

Depressive disorders: Processes leading to neurogeneration and potential novel treatments

Mood disorders are wide spread with estimates that one in seven of the population are affected at some time in their life (Kessler et al., 2012). Many of those affected with severe depressive disorders have cognitive deficits which may progress to frank neurodegeneration. There are several peripheral markers shown by patients who have cognitive deficits that could represent causative factors and could potentially serve as guides to the prevention or even treatment of neurodegeneration. Circadian rhythm misalignment, immune dysfunction and oxidative stress are key pathologic processes implicated in neurodegeneration and cognitive dysfunction in depressive disorders. Novel treatments targeting these pathways may therefore potentially improve patient outcomes whereby the primary mechanism of action is outside of the monoaminergic system. Moreover, targeting immune dysfunction, oxidative stress and circadian rhythm misalignment (rather than primarily the monoaminergic system) may hold promise for truly disease modifying treatments that may prevent neurodegeneration rather than simply alleviating symptoms with no curative intent. Further research is required to more comprehensively understand the contributions of these pathways to the pathophysiology of depressive disorders to allow for disease modifying treatments to be discovered.

Patients' Experience of Winter Depression and Light Room Treatment

Background. There is a need for more knowledge on the effects of light room treatment in patients with seasonal affective disorder and to explore patients' subjective experience of the disease and the treatment. Methods. This was a descriptive and explorative study applying qualitative content analysis. A purposeful sample of 18 psychiatric outpatients with a major depressive disorder with a seasonal pattern and a pretreatment score ≥12 on the 9-item Montgomery-Åsberg Depression self-rating scale was included (10 women and 8 men, aged 24-65 years). All patients had completed light room treatment (≥7/10 consecutive weekdays). Data was collected two weeks after treatment using a semistructured interview guide. Results. Patients described a clear seasonal pattern and a profound struggle to adapt to seasonal changes during the winter, including deterioration in sleep, daily rhythms, energy level, mood, activity, and cognitive functioning. Everyday life was affected with reduced work capacity, social withdrawal, and disturbed relations with family and friends. The light room treatment resulted in a radical and rapid improvement in all the major symptoms with only mild and transient side effects. Discussion. The results indicate that light room treatment is essential for some patients' ability to cope with seasonal affective disorder.

Circadian timing and alignment in healthy adults: associations with BMI, body fat, caloric intake and physical activity

Introduction

Disruption of circadian rhythms is one of the proposed mechanisms linking late sleep timing to obesity risk but few studies have evaluated biological markers outside of the laboratory. The goal of this study was to determine the relationship between the timing and alignment of melatonin and sleep onset (phase angle) with BMI, body fat and obesity related behaviors. We hypothesized that circadian alignment (relationship of melatonin to sleep timing) rather than circadian (melatonin) timing would be associated with higher BMI, body fat, dietary intake and lower physical activity.

Subjects/Methods

Adults with sleep duration ≥6.5 hours completed 7 days of wrist actigraphy, food diaries and SenseWear arm band monitoring. Circadian timing, measured by dim light melatonin onset (DLMO) was measured in the clinical research unit. Circadian alignment was calculated as the duration between dim light melatonin onset and average sleep onset time in the prior week (phase angle). Body fat was evaluated using dual-energy absorptiometry (DXA). Data were analyzed using bivariate correlations and multivariable regression analyses controlling for age, sex, sleep duration and evening light exposure.

Results

Participants included 97 adults (61 F, age 26.8 ± 7.3 years) with average sleep duration 443.7 (SD= 50.4) minutes. Average phase angle was 2.2 hours (SD= 1.5). Circadian alignment was associated with circadian timing (p<0.001) and sleep duration (p=.005). In multivariable analyses, later circadian timing was associated with lower BMI (p=.04). Among males only, circadian alignment was associated with percent body fat (p=.02) and higher android/gynoid fat ratio (p=0.04). Circadian alignment was associated with caloric intake (p=0.049) carbohydrate intake (p=0.04) and meal frequency (p=0.03) among both males and females.

Conclusion

Circadian timing and alignment were not associated with increased BMI or body fat, among healthy adults with ≥6.5 hours of sleep, but circadian alignment was associated with dietary intake. There may be sex differences in the relationship between circadian alignment and body fat.

Normalizing sleep quality disturbed by psychiatric polypharmacy: a single patient open trial (SPOT)

There is a growing interest in personalized and preventive medicine initiatives that leverage serious patient engagement, such as those initiated and pursued among participants in the quantified-self movement. However, many of the self-assessments that result are not rooted in good scientific practices, such as exploiting controls, dose escalation strategies, multiple endpoint monitoring, etc. Areas where individual monitoring and health assessments have great potential involve sleep and behavior, as there are a number of very problematic sleep and behavior-related conditions that are hard to treat without personalization. For example, winter depression or seasonal affective disorder (SAD) is a serious, recurrent, atypical depressive disorder impacting millions each year. In order to prevent yearly recurrence antidepressant drugs are used to prophylactically treat SAD. In turn, these antidepressant drugs can affect sleep patterns, further exacerbating the condition. Because of this, possibly unique combinatorial or ‘polypharmaceutical’ interventions involving sleep aids may be prescribed. However, little research into the effects of such polypharmacy on the long-term sleep quality of treated individuals has been pursued. Employing wireless monitoring in a patient-centered study we sought to gain insight into the influence of polypharmacy on sleep patterns and the optimal course of therapy for an individual being treated for SAD with duloxetine (Cymbalta) and temazepam. We analyzed continuous-time sleep data while dosages and combinations of these agents were varied. We found that the administration of Cymbalta led to an exacerbation of the subject’s symptoms in a statistically significant way. We argue that such analyses may be necessary to effectively treat individuals with similar overall clinical manifestations and diagnosis, despite their having a unique set of symptoms, genetic profiles and exposure histories. We also consider the limitations of our study and areas for further research.

Chronobiological Therapy for Mood Disorders

Chronobiological therapies for mood disorders include manipulations of the sleep-wake cycle such as sleep deprivation and sleep phase advance and the controlled exposure to light and darkness. Their antidepressant efficacy can overcome drug resistance and targets the core depressive symptoms including suicide, thus making them treatment options to be tried either alone or as adjunctive treatments combined with common psychopharmacological interventions. The specific pattern of mood change observed with chronobiological therapies is characterized by rapid and sustained effects, when used among themselves or combined with drugs. Effects sizes are the same reported for the most effective psychiatric treatments, but side effects are usually marginal or absent. New treatment protocols are developed to adapt them in different clinical settings. This review deals with the general principles of clinical chronobiology and the latest findings in this rapidly developing field.

Circadian Rhythms and Mood Disorders: Are the Phenomena and Mechanisms Causally Related?

This paper reviews some of the compelling evidence of disrupted circadian rhythms in individuals with mood disorders (major depressive disorder, seasonal affective disorder, and bipolar disorder) and that treatments such as bright light, designed to alter circadian rhythms, are effective in treating these disorders. Neurotransmitters in brain regions implicated in mood regulation exhibit circadian rhythms. A mouse model originally employed to identify a circadian gene has proven a potent model for mania. While this evidence is suggestive of an etiological role for altered circadian rhythms in mood disorders, it is compatible with other explanations, including that disrupted circadian rhythms and mood disorders are effects of a common cause and that genes and proteins implicated in both simply have pleiotropic effects. In light of this, the paper advances a proposal as to what evidence would be needed to establish a direct causal link between disruption of circadian rhythms and mood disorders.

Associations between seasonal sleep change and indoor tanning

Identification of risk factors for indoor tanning may ultimately aid the development of better indoor tanning prevention strategies, which is pertinent given the association between indoor tanning and skin cancer. This study aimed to examine the relationship between seasonal sleep change and indoor tanning. Female tanners (N=139) completed self-report measures including items relating to seasonal sleep changes, seasonal affective disorder (SAD), reasons for tanning, tanning during the winter months, and the Tanning Pathology Scale (TAPS), which measures problematic tanning motives and symptoms of tanning dependence. It was hypothesized that seasonal sleep change and SAD would be associated with greater indoor tanning during the winter, more tanning to improve mood and to relax, and higher scores on the TAPS. Findings indicated that more seasonal sleep change was associated with tanning to improve mood and higher scores on the TAPS. Similarly, the presence of SAD was related to tanning to improve mood, tanning to relax, and more problematic tanning.

Circadian misalignment and health

Circadian rhythms are near 24-h patterns of physiology and behaviour that are present independent of external cues including hormones, body temperature, mood, and sleep propensity. The term 'circadian misalignment' describes a variety of circumstances, such as inappropriately timed sleep and wake, misalignment of sleep/wake with feeding rhythms, or misaligned central and peripheral rhythms. The predominance of early research focused on misalignment of sleep to the biological night. However, discovery of clock genes and the presence of peripheral circadian oscillators have expanded the definitions of misalignment. Experimental studies conducted in animal models and humans have provided evidence of potential mechanisms that link misalignment to negative outcomes. These include dysregulation of feeding behaviours, changes in appetite stimulating hormones, glucose metabolism and mood. This review has two foci: (1) to describe how circadian misalignment has been defined and evaluated in laboratory and field experiments, and (2) to describe evidence linking different types of circadian misalignment to increased risk for physical (cardiovascular disease, diabetes, obesity, cancer) and psychiatric (depression, bipolar, schizophrenia, attention deficit) disorders. This review will describe the role of circadian misalignment as a risk factor for disease in the general population and in clinical populations, including circadian rhythm sleep disorders and psychiatric disorders.

Combination of light and melatonin time cues for phase advancing the human circadian clock

STUDY OBJECTIVES

Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure.

DESIGN

Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m(2))-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m(2))-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time.

SETTING

Sleep and chronobiology laboratory environment free of time cues.

PARTICIPANTS

Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD).

RESULTS

Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances.

CONCLUSION

Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders.

Genetic advances in ophthalmology: the role of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells in the circadian organization of the visual system

Daily changes in the light-dark cycle are the principal environmental signal that enables organisms to synchronize their internal biology with the 24-hour day-night cycle. In humans, the visual system is integral to photoentrainment and is primarily driven by a specialized class of intrinsically photosensitive retinal ganglion cells (ipRGCs) that express the photopigment melanopsin (OPN4) in the inner retina. These cells project through the retinohypothalamic tract (RHT) to the suprachiasmatic nuclei (SCN) of the hypothalamus, which serves as the body's master biological clock. At the same time, the retina itself possesses intrinsic circadian oscillations, exemplified by diurnal fluctuations in visual sensitivity, neurotransmitter levels, and outer segment turnover rates. Recently, it has been noted that both central and peripheral oscillators share a molecular clock consisting of an endogenous, circadian-driven, transcription-translation feedback loop that cycles with a periodicity of approximately 24 hours. This review will cover the role that melanopsin and ipRGCs play in the circadian organization of the visual system.

Health consequences of circadian disruption in humans and animal models

Daily rhythms in behavior and physiology are programmed by a hierarchical collection of biological clocks located throughout the brain and body, known as the circadian system. Mounting evidence indicates that disruption of circadian regulation is associated with a wide variety of adverse health consequences, including increased risk for premature death, cancer, metabolic syndrome, cardiovascular dysfunction, immune dysregulation, reproductive problems, mood disorders, and learning deficits. Here we review the evidence for the pervasive effects of circadian disruption in humans and animal models, drawing from both environmental and genetic studies, and identify questions for future research.

Delayed sleep phase syndrome is related to seasonal affective disorder

BACKGROUND

Both delayed sleep phase syndrome (DSPS) and seasonal affective disorder (SAD) may manifest similar delayed circadian phase problems. However, the relationships and co-morbidity between the two conditions have not been fully studied. The authors examined the comorbidity between DSPS and SAD.

METHODS

We recruited a case series of 327 DSPS and 331 controls with normal sleep, roughly matched for age, gender, and ancestry. Both DSPS and controls completed extensive questionnaires about sleep, the morningness-eveningness trait, depression, mania, seasonality of symptoms, etc.

RESULTS

The prevalences of SAD and subsyndromal SAD (S-SAD) were higher in DSPS compared to controls (χ(2)=12.65, p=0.002). DSPS were 3.3 times more likely to report SAD (odds ratio, 3.34; 95% CI, 1.41-7.93) compared to controls as defined by the Seasonal Pattern Assessment Questionnaire (SPAQ). Correspondingly, DSPS showed significantly higher seasonality scores compared to controls in mood, appetite, and energy level subscores and the global seasonality score (t=3.12, t=0.002; t=2.04, p=0.041; t=2.64, p=0.008; and t=2.15, p=0.032, respectively). Weight fluctuation during seasons and winter-summer sleep length differences were also significantly higher in DSPS than controls (t=5.16, p<0.001 and t=2.64, p=0.009, respectively). SAD and S-SAD reported significantly higher eveningness, higher depression self-ratings, and more previous mania symptoms compared to non-seasonal subjects regardless of whether they were DSPS or controls.

CONCLUSIONS

These cases suggested that DSPS is partially comorbid with SAD. These data support the hypothesis that DSPS and SAD may share a pathophysiological mechanism causing delayed circadian phase.

Circadian rhythms and depression: human psychopathology and animal models

Most organisms (including humans) developed daily rhythms in almost every aspect of their body. It is not surprising that rhythms are also related to affect in health and disease. In the present review we present data that demonstrate the evidence for significant interactions between circadian rhythms and affect from both human studies and animal models research. A number of lines of evidence obtained from human and from animal models research clearly demonstrate relationships between depression and circadian rhythms including (1) daily patterns of depression; (2) seasonal affective disorder; (3) connections between circadian clock genes and depression; (4) relationship between sleep disorders and depression; (5) the antidepressant effect of sleep deprivation; (6) the antidepressant effect of bright light exposure; and (7) the effects of antidepressant drugs on sleep and circadian rhythms. The integration of data suggests that the relationships between the circadian system and depression are well established but the underlying biology of the interactions is far from being understood. We suggest that an important factor hindering research into the underlying mechanisms is the lack of good animal models and we propose that additional efforts in that area should be made. One step in that direction could be the attempt to develop models utilizing diurnal animals which might have a better homology to humans with regard to their circadian rhythms. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Timing of sleep and its relationship with the endogenous melatonin rhythm

While much research has investigated the effects of exogenous melatonin on sleep, less is known about the relationship between the timing of the endogenous melatonin rhythm and the sleep-wake cycle. Significant inter-individual variability in the phase relationship between sleep and melatonin rhythms has been reported although the extent to which the variability reflects intrinsic and/or environmental differences is unknown. We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults. Participants chose to maintain either an early (22:30-06:30 h) or a late (00:30-08:30 h) sleep schedule for at least 3 weeks prior to an overnight laboratory visit. Saliva samples were collected under dim light (<2 lux) and controlled posture conditions to determine salivary DLMO. The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO. The mean phase relationship between sleep onset and DLMO remained constant (~2 h). The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system. The findings contribute to our understanding of individual differences in the human circadian clock and have important implications for the diagnosis and treatment of circadian rhythm sleep disorders, in particular if a greater normative range for phase angle of entrainment occurs in individuals with later sleep-wake schedules.

Melanopsin-expressing retinal ganglion cells: implications for human diseases

In the last decade, there was the seminal discovery of melanopsin-expressing retinal ganglion cells (mRGCs) as a new class of photoreceptors that subserve the photoentrainment of circadian rhythms and other non-image forming functions of the eye. Since then, there has been a growing research interest on these cells, mainly focused on animal models. Only recently, a few studies have started to address the relevance of the mRGC system in humans and related diseases. We recently discovered that mRGCs resist neurodegeneration in two inherited mitochondrial disorders that cause blindness, i.e. Leber hereditary optic neuropathy and dominant optic atrophy. The mechanism leading to mRGCs sparing in these blinding disorders, characterized by extensive and selective loss of RGCs, is currently unknown and under investigation. Other studies reported on mRGCs in glaucoma, on genetic variation of the melanopsin gene (OPN4) in seasonal affective disorder and on the role of mRGCs in migraineous photophobia. Our own data and studies from others have shown a significant reduction of mRGCs with aging. We anticipate that these studies will lead to many other investigations addressing the role of mRGCs and circadian photoreception in the pathogenesis of circadian and sleep abnormalities in neurodegenerative disorders.

Circadian effects in cancer-relevant psychoneuroendocrine and immune pathways

Human biology is deeply integrated with the rotation of the Earth: healthy physiology is synchronized with circadian cycles, while unhealthy states are often marked by poor circadian coordination. In certain cancers including breast cancer, striking circadian rhythm dysregulation extends to endocrine, immune, metabolic, and cellular function. Disruption resulting from biological and behavioral influences has been linked with higher incidence and faster tumor progression in humans and animals. The hypothalamic SCN coordinates circadian events at the tissue and cellular level, partly via glucocorticoids that regulate genes involved in tumor growth, cell proliferation, apoptosis, immune cell trafficking, and cytotoxicity. We present a revision of our previously published model of circadian effects in cancer (Sephton and Spiegel, 2003) based on evaluation of new data from divergent lines of investigation. Human clinical studies show circadian endocrine disruption may be accompanied by suppressed functional cellular immunity and overactive inflammatory responses that could promote tumor growth, angiogenesis, and metastasis. Animal data provide strong evidence of clock gene regulation of tumor cell growth. Tissue culture research demonstrates that biologically or behaviorally mediated down-regulation of clock gene expression can accelerate tumor growth. An integrated view suggests mechanisms by which circadian effects on tumor growth may be mediated. These include psychoneuroendocrine and psychoneuroimmune pathways, the relevance of which we highlight in the context of breast cancer. Taken together, data from clinical, systemic, cellular, and molecular research suggest the circadian clock is a tumor suppressor under both biological and behavioral control.

An overview of seasonal affective disorder and its treatment options

Seasonal affective disorder (SAD) is defined as a history of major depressive episodes that recur regularly at a particular time of year. Depending on the diagnostic instruments and criteria available, the reported prevalence (1%-10%) varies. Neurotransmitter abnormalities have been implicated in the pathophysiology, but they do not necessarily explain the seasonal pattern or the known chronobiological abnormalities in SAD compared with nonseasonal depression. Circadian rhythm abnormalies have been hypothesized to account for these aspects of SAD, and they provide a rationale for the therapeutic use of light therapy. Family history, twin, and molecular genetics studies suggest that hereditary factors are also involved. Light therapy and antidepressant medication are effective treatment options, with limited evidence for the efficacy of psychotherapy. Some studies demonstrate that narrow-band short wavelength "blue" light, naturalistic dawn simulation, and high-density negative air ionization are effective. Patients should be informed of the benefits of diet and exercise. Light therapy should be clinically monitored in the same manner, as it is done for other antidepressant treatments.

Circadian misalignment in mood disturbances

Recent refinements in methodology allow chronobiological researchers to answer the following questions: is there circadian misalignment in sleep and mood disturbances, and, if so, is it of the phase-advance or phase-delay type? Measurement of the dim light melatonin onset-to-midsleep interval, or phase-angle difference, in sleep and mood disorders should answer these questions. Although the phase-advance hypothesis of affective disorders was formulated three decades ago, recent studies suggest that many, if not all, mood disturbances have a circadian misalignment component of the phase-delay type, operationally defined as a delay in the dim light melatonin onset relative to the sleep/wake cycle. Phase-delayed disorders can be treated with bright light in the morning and/or low-dose melatonin in the afternoon/evening. Phase-advanced disorders can be treated with bright light in the evening and/or low-dose melatonin in the morning.