Bipolar disorder (BD) is a major mood disorder that is characterized by manic and depressive symptoms which fluctuate in severity and over time. The affective burden of the illness is compounded by cognitive, psychosocial, and occupational dysfunction, along with increased rates of suicide, medical comorbidity, and premature mortality. [1][2][3][4][5][6][7] Current guidelines for the management of BD include treatments that are limited by suboptimal efficacy rates, medication intolerance, delayed onset of action, iatrogenic mood switches, and variable patient acceptability. There is a pressing public health need for measures to combat these shortcomings. The fields of chronobiology and chronotherapy offer alternative treatment strategies which may address these limitations. The primary aim of this project was to systematically review efficacy and tolerability evidence of the major chronotherapies for BD and propose practice recommendations based on this review. This commences with a brief introduction to chronobiology to provide a rudimentary overview of the basic science which underlies this field of treatment. | Introduction to the circadian systemThe basic science of chronobiology is the study of biological rhythms, biological timekeeping systems, and their effects on human health and disease. 8 The human time-keeping system is a strongly conserved, phylogenetically ancient, hierarchically organized, and open neurobiological network. It evolved to enable organisms to anticipate and coordinate their internal physiology

Background Interest in biological clock pathways in bipolar disorders (BD) continues to grow, but there has yet to be an audit of circadian measurement tools for use in BD research and practice. Procedure The International Society for Bipolar Disorders Chronobiology Task Force conducted a critical integrative review of circadian methods that have real‐world applicability. Consensus discussion led to the selection of three domains to review—melatonin assessment, actigraphy, and self‐report. Results Measurement approaches used to quantify circadian function in BD are described in sufficient detail for researchers and clinicians to make pragmatic decisions about their use. A novel integration of the measurement literature is offered in the form of a provisional taxonomy distinguishing between circadian measures (the instruments and methods used to quantify circadian function, such as dim light melatonin onset) and circadian constructs (the biobehavioral processes to be measured, such as circadian phase). Conclusions Circadian variables are an important target of measurement in clinical practice and biomarker research. To improve reproducibility and clinical application of circadian constructs, an informed systematic approach to measurement is required. We trust that this review will decrease ambiguity in the literature and support theory‐based consideration of measurement options.

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Objective Bipolar disorder (BD) is challenging to treat, and fewer treatments are available for depressive episodes compared to mania. Light therapy is an evidence-based nonpharmacological treatment for seasonal and nonseasonal major depression, but fewer studies have examined its efficacy for patients with BD. Hence, we reviewed the evidence for adjunctive light therapy as a treatment for bipolar depression. Methods We conducted a systematic review of databases from inception to June 30, 2019, for randomized, double-blind, placebo-controlled trials of light therapy in patients with BD (CRD42019128996). The primary outcome was change in clinician-rated depressive symptom score; secondary outcomes included clinical response, remission, acceptability, and treatment-emergent mood switches. We quantitatively pooled outcomes using meta-analysis with random-effects models. Results We identified seven trials representing 259 patients with BD. Light therapy was associated with a significant improvement in Hamilton Depression Rating Scale score (standardized mean difference = 0.43, 95% confidence interval [CI], 0.04 to 0.82, P = 0.03). There was also a significant difference in favor of light therapy for clinical response (odds ratio [ OR] = 2.32; 95% CI, 1.12 to 4.81; P = 0.024) but not for remission. There was no difference in affective switches between active light and control conditions ( OR = 1.30; 95% CI, 0.38 to 4.44; P = 0.67). Study limitations included different light treatment parameters, small sample sizes, short treatment durations, and variable quality across trials. Conclusion There is positive but nonconclusive evidence that adjunctive light therapy reduces symptoms of bipolar depression and increases clinical response. Light therapy is well tolerated with no increased risk of affective switch.

A large increase in springtime solar insolation may impact the onset of bipolar disorder, especially with a family history of mood disorders. Recent societal changes that affect light exposure (LED lighting, mobile devices backlit with LEDs) may influence adaptability to a springtime circadian challenge.

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