The role of the circadian system in the etiology of depression. Neuroscience and biobehavioral reviews Circadian rhythms have evolved in almost all organisms enabling them to anticipate alternating changes in the environment. As a consequence, the circadian clock controls a broad range of bodily functions including appetite, sleep, activity and cortisol levels. The circadian clock synchronizes itself to the external world mainly by environmental light cues and can be disturbed by a variety of factors, including shift-work, jet-lag, stress, ageing and artificial light at night. Interestingly, mood has also been shown to follow a diurnal rhythm. Moreover, circadian disruption has been associated with various mood disorders and patients suffering from depression have irregular biological rhythms in sleep, appetite, activity and cortisol levels suggesting that circadian rhythmicity is crucially involved in the etiology and pathophysiology of depression. The aim of the present review is to give an overview and discuss recent findings in both humans and rodents linking a disturbed circadian rhythm to depression. Understanding the relation between a disturbed circadian rhythm and the etiology of depression may lead to novel therapeutic and preventative strategies. 10.1016/j.neubiorev.2023.105383

Effect of Circadian Rhythm on Metabolic Processes and the Regulation of Energy Balance. Serin Yeliz,Acar Tek Nilüfer Annals of nutrition & metabolism BACKGROUND:The circadian timing system or circadian clock plays a crucial role in many biological processes, such as the sleep-wake cycle, hormone secretion, cardiovascular health, glucose homeostasis, and body temperature regulation. Energy balance is also one of the most important cornerstones of metabolic processes, whereas energy imbalance is associated with many diseases (i.e., obesity, diabetes, cardiovascular disease). Circadian clock is the main regulator of metabolism, and this analysis provides an overview of the bidirectional effect of circadian rhythm on metabolic processes and energy balance. SUMMARY:The circadian timing system or circadian clock plays a crucial role in many biological processes, but the increase in activities that operate 24/7 and the common usage of television, internet, and mobile phones almost 24 h a day leads to a gradual decrease in the adequate sleeping time. According to recent research, long-term circadian disruptions are associated with many pathological conditions such as premature mortality, obesity, impaired glucose tolerance, diabetes, psychiatric disorders, anxiety, depression, and cancer progression, whereas short-term disruptions are associated with impaired wellness, fatigue, and loss of concentration. In this review, the circadian rhythm in metabolic processes and their effect on energy balance were examined. Key Messages: Circadian rhythm has a bidirectional interaction with almost all metabolic processes. Therefore, understanding the main reason affecting the circadian clock and creating treatment guidelines using circadian rhythm may increase the success of disease treatment. Chronopharmacology, chrononutrition, and chronoexercise are the novel treatment approaches in metabolic balance. 10.1159/000500071