Bipolar disorder in Asia: Illness course and contributing factors

Risk and protective factors for severe mental disorders in Asia

Among 369 diseases and injuries, the years lived with disability (YLDs) and disability-adjusted life-years (DALYs) rates for severe mental illnesses (SMIs) are within the top 20 %. Research on risk and protective factors for SMIs is critically important, as acting on modifiable factors may reduce their incidence or postpone their onset, while early detection of new cases enables prompt treatment and improves prognosis. However, as most of the studies on these factors are from Western countries, the findings are not generalizable across ethnic groups. This led us to conduct a systematic review of the risk and protective factors for SMIs identified in Asian studies. There were common factors in Asian and Western studies and unique factors in Asian studies. In-depth knowledge of these factors could help reduce disability, and the economic and emotional burden of SMIs. We hope that this review will inform future research and policy-making on mental health in Asian countries.

Research on clinical aspects of bipolar disorder: A review of Indian studies

Background

Bipolar disorder is one of the severe mental disorders that are associated with significant morbidity of the patients. Despite advancements in our understanding about the disorder, it remains a challenging proposition to treat bipolar disorder, largely since the prophylactic treatment of the disorder requires assessment of complex clinical algorithms. The revisions of the classificatory systems have also changed the conceptualization of the disorder. In this background, we conducted a review of the Indian studies conducted on the clinical aspects of bipolar disorder.

Methods

A narrative review was conducted with focus on the literature published from India. The databases searched included PubMed, Scopus, and Google Scholar, and articles published over the last 15 years by Indian authors were included for this review.

Results

In our review, we could access a substantial volume of research published from India. We could identify studies that catered to most of the relevant themes in bipolar disorder including epidemiology, etiology, comorbidities, stigma, disability, clinical course, cognitive profile, pathways to care, and recovery.

Conclusion

The research trajectory was in line with the research conducted elsewhere in the world. However, certain dissimilarities in terms of focus could also be observed. The possible reason behind this deviation could be the difference in clinical need and unique challenges faced in the management and rehabilitation of patients in bipolar disorder in Indian scenario.

What is associated with caregiver burden for adults with bipolar affective disorder: Illness severity or financial well being?

Background

Persons with bipolar affective disorder (BPAD) need long-term care and support. As most of the expenses for this are met personally by the caregivers, it will have financial implications for them. However, we do not know how much financial well-being is associated with the caregivers' burden as compared to the illness severity.

Aim

This study aimed to examine the association between financial well-being and illness severity with the caregivers' burden in the context of BPAD.

Materials and Methods

This study adopted a cross-sectional descriptive design. The first 50 consenting caregivers of persons with an International Classification of Diseases (ICD)-10 diagnosis of BPAD, who visited the National Institute of Mental Health and Neurosciences (NIMHANS) within 2019-2021, were included in the study. The patients were assessed on the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF) for the severity of the symptoms and the current level of functioning, respectively. Caregivers were assessed on the Personal Finance Well-Being Scale.

Results

In this study, the majority of caregivers were males (62%), with a median, monthly household income of Rs. 24,000, and expenditure of Rs. 12,000. The median cost of medicine was Rs. 1000 per month. The majority (64%) of patients did not have any health insurance. A total of 28 (56%) caregivers reported the cost of damage due to illness behavior. It was found that the severity of illness and current level of functioning had a significant negative correlation with caregivers' burden. The financial well-being as reflected through income and health expenditure did not have a significant correlation with the caregivers' burden.

Conclusions

Caregivers of persons with BPAD meet the treatment expenditure out of their pocket. Though they have the financial burden, it is the illness severity and functioning capacities that are associated with caregivers' burden. These findings have implications for mental health care in persons with BPAD.

Chronotype is associated with affective temperaments, clinical severity and worse treatment outcomes in bipolar disorders: results from a two-center, cross-sectional study

OBJECTIVE

The present study was aimed at investigating the clinical correlates of evening chronotype in a population of subjects suffering from bipolar disorders (BD).

METHODS

We assessed chronotype using the Morningness-Eveningness Questionnaire. We administered the brief Temperament Evaluation of Memphis, Pisa, and San Diego, the Barratt Impulsiveness Scale, and the Alda Scale to evaluate affective temperaments, impulsiveness, and response to mood stabilisers. We performed bivariate analyses and ran a logistic regression model to analyse clinical variables associated with evening chronotype.

RESULTS

In our sample (n = 178), subjects with an evening chronotype (n = 56, 31.5%) more often suffered from BD type I and reported higher prevalence of seasonality, antidepressant-induced mood switches, psychotic, aggressive, mixed, and anxiety features, and substance use disorders. The number of lifetime suicide attempts and mood episodes was higher in this subgroup. Depressive, cyclothymic, irritable, and anxious temperament scores were higher among evening-chronotype subjects, who also displayed greater levels of impulsiveness and worse treatment response. At the logistic regression, evening chronotype was associated with depressive and irritable temperaments.

CONCLUSIONS

Subjects with evening chronotype display higher clinical severity and worse BD course. Clinicians should evaluate the presence of evening chronotype in BD subjects, especially in those with irritable or depressive temperament.Key pointsEvening chronotype is a frequent clinical feature in subjects suffering from bipolar disorders (BD);Affective temperaments, particularly depressive and irritable, are associated with evening chronotype in BD;Evening chronotype underpins higher severity of the clinical picture in BD, as well as a worse response to mood stabiliser treatment;Circadian preferences should be systematically assessed in subjects suffering from BD, with particular attention to evening preference.

Bipolar disorder in the International Classification of Diseases-Eleventh version: A review of the changes, their basis, and usefulness

The World Health Organization’s 11^th revision of the International Classification of Diseases (ICD-11) including the chapter on mental disorders has come into effect this year. This review focuses on the “Bipolar or Related Disorders” section of the ICD-11 draft. It describes the benchmarks for the new version, particularly the foremost principle of clinical utility. The alterations made to the diagnosis of bipolar disorder (BD) are evaluated on their scientific basis and clinical utility. The change in the diagnostic requirements for manic and hypomanic episodes has been much debated. Whether the current criteria have achieved an optimum balance between sensitivity and specificity is still not clear. The ICD-11 definition of depressive episodes is substantially different, but the lack of empirical support for the changes has meant that the reliability and utility of bipolar depression are relatively low. Unlike the Diagnostic and Statistical Manual of Mental Disorders, 5^th edition (DSM-5), the ICD-11 has retained the category of mixed episodes. Although the concept of mixed episodes in the ICD-11 is not perfect, it appears to be more inclusive than the DSM-5 approach. Additionally, there are some uncertainties about the guidelines for the subtypes of BD and cyclothymic disorder. The initial results on the reliability and clinical utility of BD are promising, but the newly created diagnostic categories also appear to have some limitations. Although further improvement and research are needed, the focus should now be on facing the challenges of implementation, dissemination, and education and training in the use of these guidelines.

Which patients with bipolar depression receive antidepressant augmentation? Results from an observational multicenter study

BACKGROUND

To identify demographic and clinical characteristics of bipolar depressed patients who require antidepressant (AD) augmentation, and to evaluate the short- and long-term effectiveness and safety of this therapeutic strategy.

METHODS

One hundred twenty-two bipolar depressed patients were consecutively recruited, 71.7% of them received mood stabilizers (MS)/second-generation antipsychotics (SGA) with AD-augmentation and 28.3% did not. Patients were evaluated at baseline, and after 12 weeks and 15 months of treatment.

RESULTS

The AD-augmentation was significantly higher in patients with bipolar II compared with bipolar I diagnosis. Patients with MS/SGA + AD had often a seasonal pattern, depressive polarity onset, depressive index episode with anxious features, a low number of previous psychotic and (hypo)manic episodes and of switch. They had a low irritable premorbid temperament, a low risk of suicide attempts, and a low number of manic symptoms at baseline. After 12 weeks of treatment, 82% of patients receiving ADs improved, 58% responded and 51% remitted, 3.8% had suicidal thoughts or projects, 6.1% had (hypo)manic switch, and 4.1% needed hospitalization. During the following 12 months, 92% of them remitted from index episode, 25.5% did not relapse, and 11% needed hospitalization. Although at the start advantaged, patients with AD-augmentation, compared with those without AD-augmentation, did not significantly differ on any outcome as well on adverse events in the short- and long-term treatment.

CONCLUSION

Our findings indicate that ADs, combined with MS and/or SGA, are short and long term effective and safe in a specific subgroup for bipolar depressed patients.

The nosological status of unipolar mania and hypomania within UK Biobank according to objective and subjective measures of diurnal rest and activity

BACKGROUND

There is uncertainty whether unipolar mania is a discrete sub-type of bipolar disorder. Disrupted rest/activity rhythms are a key feature of bipolar disorder (BD) but have not been well characterised in unipolar mania/hypomania (UM). We compared subjective and objective rest/activity patterns, demographic and mental health outcomes across BD, UM and control groups.

METHODS

UK residents aged 37-73 years were recruited into UK Biobank from 2006 to 2010. BD, UM and control groups were identified via a mental health questionnaire. Demographic, mental health and subjective sleep outcomes were self-reported. Accelerometery data were available for a subset of participants, and objective measures of sleep and activity were derived.

RESULTS

A greater proportion of males met UM criteria, and more females were in the BD group. Both BD and UM groups had poor mental health outcomes vs. controls. Objectively measured activity differed between all three groups: UM had highest levels of activity and BD lowest. The UM group had shorter sleep duration compared to controls. Subjective rest/activity measures showed that both mood disorder groups (compared to controls) had later chronotype preference, more disturbed sleep and increased difficulty getting up in the morning. However, the UM group were more likely to report an early chronotype compared to BD and control groups.

CONCLUSIONS

BD and UM share features in common, but key differences support the proposition that UM may be a distinct and more clinically homogenous disorder. UM was characterised by a higher proportion of males, early chronotype, increased activity and shorter sleep duration.

Course and outcome of bipolar I disorder among Indian patients: A retrospective life-chart study

BACKGROUND

Indian studies on the course and outcome of bipolar disorder (BD) are scarce and their methodologies vary. Nevertheless, differences from Western ones have been noted.

METHODS

A systematic random sample of 200 patients with BD attending a general hospital psychiatric unit was chosen. They were assessed using the clinician and self-rated versions of the National Institute of Mental Health-Retrospective Life Charts, the lifetime version of the Columbia Suicide Severity Rating Scale, the Medication Adherence Questionnaire, the Indian Disability Evaluation and Assessment Scale, and the Presumptive Stressful Life Events Scale.

RESULTS

The mean age of onset of BD was 26 years. About 11%-13% of the illness was spent in acute episodes, mostly in depression (60%). Episode frequency was 0.4-0.6 annually. The first episode was more likely to be manic, and manic episodes outnumbered depressive episodes. The average duration of episodes was 3 months. Depressive episodes were longer and the time spent in depression was greater than mania. Psychotic symptoms (48%), a mania-depression-interval pattern (61%), and recurrent mania (19%) were common while rapid cycling and seasonal patterns were uncommon. Comorbidity (40%), functional impairment (77%), and lifetime nonadherence (58%) were high, whereas lifetime suicide attempts (16%) were low. Stressful life events were very common prior to episodes (80%), particularly early in the illness.

CONCLUSION

This study suggests differences between Indian and Western patients in the demographic profile and the course and outcome of BD. A more benign presentation in the current study including Indian studies is indicated by their later age of presentation and illness onset, higher rates of marriage, education, and employment, a mania predominant course, lower rates of rapid cycling, comorbidity, and suicidal attempts. Factors associated with better outcomes such as longer time to recurrence, Manic Depressive pattern of illness, and low rates of hospitalizations also appear to be commoner in our study and also in other Indian studies.

Substance use disorders in bipolar disorders: Clinical correlates and treatment response to mood stabilizers

BACKGROUND

Substance use disorders (SUD) in bipolar disorders (BD) present relevant impact on psychopathological features and illness course. The present study was aimed at analyzing the clinical correlates of this comorbidity.

METHODS

In- and outpatients suffering from BD were recruited. Socio-demographic and clinical characteristics were collected. Subjects underwent a psychopathological assessment evaluating affective temperaments and impulsiveness. The appraisal of treatment response to mood stabilizers was conducted with the Alda Scale. Bivariate analyses were used to compare subjects suffering from BD with (SUD-BD) or without comorbid SUD (nSUD-BD) (p<0.05). A logistic regression model was performed to identify specific correlates of SUD in BD.

RESULTS

Among the 161 included subjects, 63 (39.1%) were diagnosed with comorbid SUD. SUD-BD subjects showed younger age at onset (p = 0.003) and higher prevalence of BD type I diagnosis (BDI) (p<0.001). Furthermore, lifetime mixed features (p<0.001), psychotic symptoms (p<0.001), suicide attempts (p = 0.002), aggression (p = 0.003), antidepressant-induced manic switch (p = 0.003), and poor treatment response (p<0.001) were more frequent in the SUD-BD subgroup. At the logistic regression, SUD revealed a positive association with BD type I diagnosis (Odds Ratio (OR) 4.77, 95% CI 1.66-13.71, p = 0.004) and mixed features (OR 2.54, 95% CI 1.17-5.53, p = 0.019).

LIMITATIONS

The cross-sectional study design and the relatively small sample size may limit the generalizability of the findings. The retrospective evaluation of comorbid SUD could have biased the outcome assessment.

CONCLUSIONS

Subjects with BD and SUD are characterized by higher clinical severity and require careful assessment of treatment response.

Chronbiologically-based sub-groups in bipolar I disorder: A latent profile analysis

BACKGROUND

Bipolar disorder presents with significant phenotypic heterogeneity. The aim of this study was to investigate whether bipolar disorder, type I (BDI) subjects could be meaningfully classified into homogeneous groups according to activity, sleep, and circadian characteristics using latent profile analysis (LPA). We hypothesized that distinct BDI sub-groups would be identified based primarily on circadian-associated markers.

MATERIALS AND METHODS

105 individuals with BDI were included in the study. Seventeen activity, sleep, and circadian characteristics were assessed via actigraphy and clinical assessments. LPA was conducted to stratify our sample into homogenous sub-groups. Differences between groups on demographic, clinical, activity, sleep, and circadian characteristics were explored.

RESULTS

Two distinct groups were identified, a High Chronobiological Disturbance group (HCD) (56%, N = 59) and a Low Chronobiological Disturbance group (LCD) (41%; N = 46). Circadian variables were the defining characteristics in sub-group determination. Large effect sizes and magnitudes of association were noted in circadian variables between HCD and LCD sub-groups. Several circadian rhythm variables accounted for a large percentage of the variance between HCD and LCD sub-groups. No differences were noted between sub-groups on demographic characteristics and the psychiatric medications currently in use. Mood state did not significantly impact sub-group differences.

LIMITATIONS

The protocol was cross-sectional in design. Longitudinal studies are required to determine the stability of the identified sub-groups.

CONCLUSION

LPA was able to identify sub-groups in BDI with circadian variables being the most distinguishing factors in determining sub-group class membership. Future research should explore the role that circadian characteristics can play in defining sub-phenotypes of bipolar disorder.

Self-Reported Low Lithium Adherence Among Chinese Patients with Bipolar Disorder in Shenzhen: A Cross-Sectional Study

BACKGROUND

Lithium has been widely used to treat bipolar disorder (BD), although its adherence is rarely reported in China. This study aimed to explore the rate of lithium adherence and its associated factors in patients with BD, which has rarely been reported in China.

METHODS

We conducted a cross-sectional study among patients in Shenzhen Mental Health Center (Shenzhen Kangning Hospital), who were aged 12 years or above, were diagnosed with BD based on the International Classification of Diseases, tenth edition (ICD-10), and had been on lithium for at least 1 month. We collected information on sociodemographic and clinical characteristics and on knowledge about and attitudes toward lithium. We also investigated patients' concerns while taking lithium and where they can and wish to obtain information on lithium.

RESULTS

Of the 244 enrolled patients and 221 patients aged 18 years or older, 52% and 50% disclosed low adherence to lithium, respectively. Factors associated with poor lithium adherence were a younger age (odds ratio (OR): 0.962, 95% confidence interval (CI): 0.933-0.992), female sex (OR: 2.171, 95% CI: 1.146-4.112), and no hospitalization history (OR: 0.389, 95% CI: 0.217-0.689) for the full sample, and more years of education (OR: 4.086, 95% CI: 1.397-11.946) and fewer hospitalizations (OR: 0.615, 95% CI: 0.467-0.809) for patients aged 18 years or older. Less knowledge of periodic tests conducted during lithium treatment played a critical role in low lithium adherence (regression analysis of the full sample: OR: 0.642, 95% CI: 0.532-0.775, regression analysis of subgroups: OR: 0.609, 95% CI: 0.500-0.742). The treatment duration was a major concern among patients on lithium, and patients preferred obtaining lithium-associated information through health services and WeChat.

CONCLUSION

The rate of lithium adherence was low in this study. Psychoeducation to increase lithium compliance should mainly focus on patients who are young and provide thorough background information on lithium. Health services should actively provide lithium-associated information. A greater need for medication information based on WeChat was observed, implying its potential role in adherence-related psychoeducation.

Gender Differences in Clinical Characteristics and Comorbidities in Bipolar Disorder: a Study from South India

The clinical features and course of bipolar disorder differ between women and men; however, studies are limited in Indian population. The objective of this study was to identify gender differences in patients with bipolar disorder. This was a cross-sectional, hospital-based observational study conducted over a period of 25 months. The sample consisted of 110 males and 90 females with a diagnosis of bipolar disorder according to ICD-10 Diagnostic Criteria for Research. Socio-demographic and clinical details were collected using semi-structured proforma. All patients were evaluated on Mini International Neuropsychiatric Interview Plus, Presumptive Stressful Life Events Scale and Clinical Global Impression. Sample consisted of 55% men and 45% women. The total number of episodes was similar between genders, however, the number of manic episodes (p = 0.004) was significantly more in males and the number of depressive (p = 0.003) and mixed episodes (p = 0.018) were significantly more in females. Majority of males had first episode of mania, whereas, first episode in females were mostly depressive (p < 0.001). Comorbid physical disorders were seen in 61.1% females and 40% males. Bipolar disorder subtype, episode types and number varied across gender. Co-morbid hypothyroidism, migraine, and obesity are seen more often in women and substance use was higher in men.

Homocysteine, chronotype and clinical course in bipolar disorder patients

Purpose: Higher homocysteine (HHcy) levels have been detected in bipolar disorder (BD) patients, and BD patients show circadian rhythm disorders even during remission. Here, we determined the homocysteine (Hcy) levels and chronotype of patients with BD during remission and investigated whether this was related to the clinical course of the disease. Materials and methods: In total, 80 BD outpatients were included. Clinical evaluation was conducted using the Hamilton Depression Rating Scale (HDRS), Young Mania Rating Scale (YMRS), Pittsburgh Sleep Quality Index (PSQI) and the Morningness-Eveningness Questionnaire (MEQ). Hcy, folic acid, vitamin B12 levels and protein consumption the day before clinical evaluation were measured.Results and conclusions: HHcy was found in 11 patients (8.8%), most of whom were males (n = 8, 72.7%). During the course of BD, patients with HHcy had significantly more mixed episodes than patients without HHcy (p = .007, z = -2696). In addition, patients with HHcy had significantly lower MEQ scores than patients without HHcy (p = .04, t = 2018). There was no significant difference in chronotype between patients with and without HHcy. The HHcy group had significantly lower levels of vitamin B12 (p = .003, t = 2870). There were no statistically significant differences in daily protein intake and folic acid levels between HHcy and non-HHcy groups. Our study showed a significant relationship between the number of mixed episodes and HHcy. In terms of potential confounds, patients who abused alcohol were excluded, but alcohol consumption was not evaluated. This result should be considered in BD and should be evaluated in larger samples of BD patients.

Chronotypes and affective disorders: A clock for mood?

Affective disorders are often accompanied by circadian rhythm disruption and the major symptoms of mental illness occur in a rhythmic manner. Chronotype, also known as circadian preference for rest or activity, is believed to exert a substantial influence on mental health. Here, we review the connection between chronotypes and affective disorders, and discuss the potential underlying mechanisms between these two phenomena.

Using Chronobiological Phenotypes to Address Heterogeneity in Bipolar Disorder

Bipolar disorder (BD) is a neuropsychiatric mood disorder characterized by recurrent episodes of mania and depression in addition to disruptions in sleep, energy, appetite, and cognitive functions-rhythmic behaviors that typically change on daily cycles. BD symptoms can also be provoked by seasonal changes, sleep, and/or circadian disruption, indicating that chronobiological factors linked to the circadian clock may be a common feature in the disorder. Research indicates that BD exists on a clinical spectrum, with distinct subtypes often intersecting with other psychiatric disorders. This heterogeneity has been a major challenge to BD research and contributes to problems in diagnostic stability and treatment outcomes. To address this heterogeneity, we propose that chronobiologically related biomarkers could be useful in classifying BD into objectively measurable phenotypes to establish better diagnoses, inform treatments, and perhaps lead to better clinical outcomes. Presently, we review the biological basis of circadian time keeping in humans, discuss the links of BD to the circadian clock, and pre-sent recent studies that evaluated chronobiological measures as a basis for establishing BD phenotypes. We conclude that chronobiology may inform future research using other novel techniques such as genomics, cell biology, and advanced behavioral analyses to establish new and more biologically based BD phenotypes.

Comorbidity of bipolar and anxiety disorders: An overview of trends in research

Over the last three decades burgeoning research has shown that anxiety disorder comorbidity is not only highly prevalent in bipolar disorder (BD), but it also adversely impacts the course, outcome, and treatment of BD. The present review provides an overview of the current trends in research on comorbid anxiety and BDs based on prior reviews and meta-analyses (n = 103), epidemiological surveys, and large-scale clinical studies. The results reiterated the fact that at least half of those with BD are likely to develop an anxiety disorder in their lifetimes and a third of them will manifest an anxiety disorder at any point of time. All types of anxiety disorders were equally common in BD. However, there was a wide variation in rates across different sources, with most of this discrepancy being accounted for by methodological differences between reports. Comorbid anxiety disorders negatively impacted the presentation and course of BD. This unfavourable clinical profile led to poorer outcome and functioning and impeded treatment of BD. Despite the extensive body of research there was paucity of data on aetiology and treatment of anxiety disorder comorbidity in BD. Nevertheless, the substantial burden and unique characteristics of this comorbidity has important clinical and research implications.

Stressful Life Events and Relapse in Bipolar Affective Disorder: A Cross-Sectional Study from a Tertiary Care Center of Southern India

BACKGROUND

Bipolar affective disorder (BAD) is a severe mental illness which results in serious lifelong struggles and challenges. The full impact of stressful life events (SLEs) on the course of BAD is poorly understood.

MATERIALS AND METHODS

A cross-sectional study was conducted on 128 consecutive patients with BAD currently admitted with a relapse. Our objectives were (1) to estimate the proportion, type, and timing of preonset SLEs in relapsed BAD patients and (2) to study the association between SLEs and selected clinical variables in this group. Semi-structured proforma, Young Mania Rating Scale, Hamilton Rating Scale for Depression, Presumptive Stressful Life Events Scale, and Brief Psychiatric Rating Scale were used. Statistical analysis was done using R software for Windows.

RESULTS

About 69.5% (89/128) of patients reported preonset SLEs - among which 50 (56.2%) had mania and 39 (43.8%) had depression. Conflict with in-laws and financial problems were the commonly reported SLEs. The mean duration between SLEs and the relapse was 19.73 ± 4.8 days. BPRS score was significantly high in subjects with preonset SLEs (P = 0.022). No significant association was detected between SLEs and the type of episode during relapse (P = 0.402).

CONCLUSION

This study emphasizes the significance of SLEs in the relapse and longitudinal course of BAD. Understanding the association of SLEs and relapse in BAD will help in predicting further relapses and developing newer pharmacological and nonpharmacological measures targeting this aspect, thereby maximizing both symptom reduction and quality of life in patients with BAD.

Chronotype and Mental Health: Recent Advances

PURPOSE OF REVIEW

Evening chronotype is increasingly recognized as a correlate of, and perhaps a contributor to, mental illness. The current review evaluates recent evidence for the association between chronotype and mental illness and putative mechanisms underlying the association, while highlighting methodological advances and areas of research that are relatively under-examined in the literature.

RECENT FINDINGS

While evening chronotype is most consistently associated with severity of mood disorder symptoms, emerging evidence implicates evening chronotype as a transdiagnostic correlate of substance use severity, anxiety symptoms, attentional difficulties, and maladaptive behaviors such as aggression. Longitudinal studies point to the possibility that evening chronotype precedes problematic substance use, depression, and anxiety. Neural processes related to reward and affective regulation may underlie associations between evening chronotype and illness. The literature on chronotype and mental illness has evolved to (1) include associations with a broader range of psychiatric symptom profiles; (2) explore underlying mechanisms; and (3) expand on earlier research using objective measures and more sophisticated study designs. In addition to further mechanistic research, additional work is needed to examine the stability and key subcomponents of the chronotype construct, as well as more attention to pediatric and special populations. This research is needed to clarify the chronotype-mental health relationship, and to identify how, when, and what aspects of chronotype can be targeted via therapeutic interventions.