Circadian rhythm disruptions: A possible link of bipolar disorder and endocrine comorbidities

Associations between light at night and mental health: A systematic review and meta-analysis

Light at night (LAN) disrupts the circadian rhythm by altering the natural light-dark cycle. With increasing interest in the relationship between LAN and mental health, there is value in an updated systematic review and meta-analysis considering prominent mental health conditions that also critically appraises LAN exposure assessment. We conducted a systematic review of six databases, two registries, and Google Scholar to identify studies examining the associations between indoor and outdoor LAN exposure (high vs. low exposure) and mental health outcomes (depression, bipolar disorder, anxiety, and schizophrenia), completing inverse-variance random-effects meta-analyses. Nineteen studies with a total population of 556,861 were included in the review. LAN exposure was associated with increased odds of depression prevalence (odds ratio [OR]: 1.18; 95 % confidence interval [CI]: 1.09 to 1.28), with stronger associations for bedside (OR: 1.45; 95 % CI: 1.03 to 2.04) or wrist-measured indoor LAN (OR: 1.30; 95 % CI: 1.22 to 1.38) than satellite-measured outdoor LAN exposure (OR: 1.10; 95 % CI: 1.04 to 1.17) and in older adults (OR: 1.56; 95 % CI: 1.24 to 1.96) compared to general adults (OR: 1.16; 95 % CI: 1.06 to 1.28) or youth (OR: 1.07; 95 % CI: 0.99 to 1.16). LAN exposure was also associated with an increased prevalence of bipolar disorder (OR: 1.19; 95 % CI: 1.08 to 1.31) and anxiety (OR: 1.10; 95 % CI: 1.02 to 1.20) and increased incidence of anxiety (hazard ratio [HR]: 1.08; 95 % CI: 1.02 to 1.15) and schizophrenia (HR: 1.55; 95 % CI: 1.01 to 2.39); however, the incidence of depression did not achieve statistical significance (HR: 1.53; 95 % CI: 0.98 to 2.38). Overall, our results suggest that LAN exposure influences adverse mental health conditions, with differences in results appreciated for depression prevalence depending on how LAN exposure was measured. Additional research is needed on the effects of LAN given its undoubted interest in the prevention and treatment of mental disorders.

Circadian de(regulation) in physiology: implications for disease and treatment

Time plays a crucial role in the regulation of physiological processes. Without a temporal control system, animals would be unprepared for cyclic environmental changes, negatively impacting their survival. Experimental studies have demonstrated the essential role of the circadian system in the temporal coordination of physiological processes. Translating these findings to humans has been challenging. Increasing evidence suggests that modern lifestyle factors such as diet, sedentarism, light exposure, and social jet lag can stress the human circadian system, contributing to misalignment; i.e., loss of phase coherence across tissues. An increasing body of evidence supports the negative impact of circadian disruption on several human health parameters. This review aims to provide a comprehensive overview of how circadian disruption influences various physiological processes, its long-term health consequences, and its association with various diseases. To illustrate the relevant consequences of circadian disruption, we focused on describing the many physiological consequences faced by shift workers, a population known to experience high levels of circadian disruption. We also discuss the emerging field of circadian medicine, its founding principles, and its potential impact on human health.

The emerging neuroimmune hypothesis of bipolar disorder: An updated overview of neuroimmune and microglial findings

Bipolar disorder (BD) is a severe and multifactorial disease, with onset usually in young adulthood, which follows a progressive course throughout life. Replicated epidemiological studies have suggested inflammatory mechanisms and neuroimmune risk factors as primary contributors to the onset and development of BD. While not all patients display overt markers of inflammation, significant evidence suggests that aberrant immune signaling contributes to all stages of the disease and seems to be mood phase dependent, likely explaining the heterogeneity of findings observed in this population. As the brain's immune cells, microglia orchestrate the brain's immune response and play a critical role in maintaining the brain's health across the lifespan. Microglia are also highly sensitive to environmental changes and respond to physiological and pathological events by adapting their functions, structure, and molecular expression. Recently, it has been highlighted that instead of a single population of cells, microglia comprise a heterogeneous community with specialized states adjusted according to the local molecular cues and intercellular interactions. Early evidence has highlighted the contribution of microglia to BD neuropathology, notably for severe outcomes, such as suicidality. However, the roles and diversity of microglial states in this disease are still largely undermined. This review brings an updated overview of current literature on the contribution of neuroimmune risk factors for the onset and progression of BD, the most prominent neuroimmune abnormalities (including biomarker, neuroimaging, ex vivo studies) and the most recent findings of microglial involvement in BD neuropathology. Combining these different shreds of evidence, we aim to propose a unifying hypothesis for BD pathophysiology centered on neuroimmune abnormalities and microglia. Also, we highlight the urgent need to apply novel multi-system biology approaches to characterize the diversity of microglial states and functions involved in this enigmatic disorder, which can open bright perspectives for novel biomarkers and therapeutic discoveries.

Chronotype and Cardiometabolic Parameters in Patients with Bipolar Disorder: Preliminary Findings

Cardiometabolic alterations are very common in bipolar disorder (BD). The aim of this study was to investigate the relationship between chronotype and cardiometabolic parameters in patients with a primary diagnosis of BD. This study is an observational clinical investigation including 170 subjects consecutively admitted to the Psychiatric Inpatient Unit of the IRCCS Ospedale Policlinico San Martino (Genoa, Italy), recruited over a period of 48 months. A psychometric tool assessing chronotype was administered and blood tests were performed. Furthermore, the atherogenic coefficient ((total cholesterol-HDL cholesterol)/HDL cholesterol), and Castelli risk index-I (total cholesterol/HDL cholesterol) and -II (LDL cholesterol/HDL cholesterol) were calculated. Patients with BD and an eveningness chronotype showed a higher body mass index, total and low-density lipotrotein cholesterol compared to patients with BD and an intermediate or morning chronotype. Furthermore, the Atherogenic Coefficient and Castelli Risk-Index I-II were found to be higher in bipolar patients with an evening chronotype. The role of chronotype in the development of obesity and cardiovascular risk is, therefore, a relationship worth being investigated, especially in the context of BD, to ameliorate the clinical and therapeutic approach, aiming at increasing the quality of life and reducing the mortality.

Seasonal Variation of Laboratory Animals as a Consideration for Research Reproducibility

Laboratory rodents are generally maintained under standardized conditions in order to control the effects of extrinsic factors on research. However, despite attempts to standardize conditions, variability can nonetheless confound efforts directed toward research reproducibility. Here we explore some of the existing literature on the potential impact of seasonal variability as an extrinsic factor that can potentially impact research results. We discuss the influence of seasonal changes in association with an internal clock mechanism that might account for such variation, noting that the mechanisms and interactions of seasonal and internal time-keeping remain largely undetermined. Finally, we speculate that seasonal changes experienced by personnel who handle animals may influence the animals in ways that result in physiologic and behavioral changes.

Factors associated with psychiatric and physical comorbidities in bipolar disorder: a nationwide multicenter cross-sectional observational study

BACKGROUND

Bipolar disorder (BD) is a chronic and disabling affective disorder with significant morbidity and mortality. Despite the high rate of psychiatric and physical health comorbidity, little is known about the complex interrelationships between clinical features of bipolar illness and comorbid conditions. The present study sought to examine, quantify and characterize the cross-sectional associations of psychiatric and physical comorbidities with selected demographic and clinical characteristics of adults with BD.

METHODS

A nationwide multicenter cross-sectional observational epidemiological study conducted from October 2015 to March 2017 in Slovakia.

RESULTS

Out of 179 study participants [median age 49 years (interquartile range IQR 38-58); 57.5% females], 22.4% were free of comorbidity, 42.5% had both psychiatric and physical comorbidities, 53.6% at least one psychiatric comorbidity, and 66.5% at least one physical comorbidity. The most prevalent were the essential hypertension (33.5%), various psychoactive substance-related disorders (21.2%), specific personality disorders (14.6%), obesity (14.5%), and disorders of lipoprotein metabolism (14%). The presence of an at least one physical comorbidity, atypical symptoms of BD, and unemployed status were each associated with an at least one psychiatric comorbidity independent of sex, early onset of BD (age of onset <35 years), BD duration and pattern of BD illness progression (p < 0.001). The presence of various psychoactive substance-related disorders, BD duration, atypical symptoms of BD, unemployed status, pension, female sex, and not using antipsychotics were each associated with an at least one physical comorbidity independent of the pattern of BD illness progression (p < 0.001). In several other multiple regression models, the use of antipsychotics (in particular, olanzapine) was associated with a decreased probability of the essential hypertension and predicted the clinical phenotype of comorbidity-free BD (p < 0.05).

CONCLUSION

This cross-national study has reported novel estimates and clinical correlates related to both the comorbidity-free phenotype and the factors associated with psychiatric and physical comorbidities in adults with BD in Slovakia. The findings provide new insights into understanding of the clinical presentation of BD that can inform clinical practice and further research to continue to investigate potential mechanisms of BD adverse outcomes and disease complications onset.