Light exerts powerful biological effects on mood regulation. Whereas the source of photic information affecting mood is well established at least via intrinsically photosensitive retinal ganglion cells (ipRGCs) secreting the melanopsin photopigment, the precise circuits that mediate the impact of light on depressive behaviors are not well understood. This review proposes two distinct retina–brain pathways of light effects on mood: (i) a suprachiasmatic nucleus (SCN)-dependent pathway with light effect on mood via the synchronization of biological rhythms, and (ii) a SCN-independent pathway with light effects on mood through modulation of the homeostatic process of sleep, alertness and emotion regulation: (1) light directly inhibits brain areas promoting sleep such as the ventrolateral preoptic nucleus (VLPO), and activates numerous brain areas involved in alertness such as, monoaminergic areas, thalamic regions and hypothalamic regions including orexin areas; (2) moreover, light seems to modulate mood through orexin-, serotonin- and dopamine-dependent pathways; (3) in addition, light activates brain emotional processing areas including the amygdala, the nucleus accumbens, the perihabenular nucleus, the left hippocampus and pathways such as the retina–ventral lateral geniculate nucleus and intergeniculate leaflet–lateral habenula pathway. This work synthetizes new insights into the neural basis required for light influence mood

The Seasonal Pattern Assessment Questionnaire (SPAQ), by Rosenthal et al. (1984), is by far the most used questionnaire to evaluate seasonal effects on mood and behavior. It includes a general seasonality score (GSS), composed of 6 items, from which cutoffs have been established to screen for seasonal affective disorder (SAD). However, it has never been validated in French and associations with circadian rhythm and symptoms of depression and bipolarity remain unclear. In this study, including 165 subjects (95 controls and 70 patients with depression or bipolar disorder), we confirmed the validity of the French version of the SPAQ, with a two-factor structure (a psychological factor: energy, mood, social activity and sleep length; and a food factor: weight and appetite) and a good fit was observed by all indicators. Mood and social activity dimensions were significantly affected by seasons in the depressed/bipolar group and a stronger global seasonality score (GSS) was associated with more severe phenotypes of depression and mania. Subjects meeting SAD and subsyndromal-SAD criteria also showed a delayed circadian rhythm compared to controls. Simple tools, such as the SPAQ, can aid the identification of significant seasonal changes and have direct implications on therapeutics including the use of bright light therapy in order to enhance personalized treatments, but also to prevent adverse seasonal effects.

Background: One of the challenges in bipolar disorder (BD) lies in early detection of the illness and its recurrences, to improve prognosis. Sleep disturbances (SD) have been proposed as reliable predictive markers of conversion. While preliminary studies have explored the relationship between SD and the onset of mood episodes, the results remain heterogeneous and a few have specifically examined patients' perception of prodromal symptoms and their progression until the episode occurs. Identifying prodromes represents a crucial clinical challenge, as it enables early intervention, thereby reducing the severity of BD. Therefore, the objective of this study is to better characterize and evaluate the progressive nature of SD as prodromal symptoms of mood episodes, and patients' perception of it.Methods: Patients diagnosed with BD, either hospitalized or seeking treatment for a (hypo)manic or depressive episode benefited from standardized questionnaires, structured interviews, and self‐report questionnaires to evaluate SD prior to the current episode, as well as sociodemographic and clinical information.Results: Out of the 41 patients included, 59% spontaneously reported SD prior to the episode, appearing 90 days before depression and 35 days before mania (pre‐indexed/spontaneous reports: 51.22% insomnia complaints, 4.88% hypersomnolence complaints, 7.32% parasomnias, 2.44% sleep movements). After inquiry about specific SD, the percentage of patients reporting prodromal SD increased significantly to 83%, appearing 210 days before depression and 112.5 days before mania (post‐indexed reports: 75.61% presented with insomnia complaints appearing 150 days before depression and 20 days before mania, 46.34% had hypersomnolence complaints appearing 60 days before depression, 43.9% had parasomnias appearing 210 days before depression and 22.5 days before mania, 36.59% had sleep movements appearing 120 days before depression and 150 days before mania). Of note, bruxism appeared in 35% of patients before mania, and restless legs syndrome in 20% of patients before depression.Conclusion: This study highlights the very high prevalence of SD prior to a mood episode in patients with BD with differences between depressive and manic episodes. The more systematic screening of sleep alterations of the prodromal phase improved the recognition and characterization of different symptoms onset by patients. This underscores the need for precise questioning regarding sleep patterns in patients, to better identify the moment of transition toward a mood episode, referred to as "Chronos syndrome". The study emphasizes the importance of educating patients about the disorder and its sleep prodromal symptoms to facilitate early intervention and prevent recurrences.

The aim of this study was to estimate the prevalence of metabolic syndrome (MetS) and its components in a cohort of French patients with treatment-resistant depression (TRD) and to determine correlations with sociodemographic, clinical, and treatment-related factors. From 2012 to 2018, 205 patients who met DSM-IV criteria for major depressive episode with moderate-to-severe symptoms (Montgomery-Asberg Depression Rating Scale score ≥ 20), and at least Stage II resistance according to Thase and Rush criteria were enrolled in the FondaMental Advanced Centers of Expertise in Resistant Depression (FACE-DR) cohort. Data on sociodemographic and clinical characteristics, lifestyle information, and treatment and comorbidities were collected, and a blood sample was drawn. MetS was defined according to the criteria of the International Diabetes Federation. Overall, 38% of individuals with TRD met criteria for MetS. The frequency of MetS was significantly higher in men than in women only for patients aged 40 years or older (46.3% vs 35.2%, P = .0427). Moreover, whereas the management for diabetes was good, less than one-third of the patients with high blood pressure or dyslipidemia were treated for these conditions. Multivariate analysis showed that individuals with abnormal plasma c-reactive protein levels had a 3-fold increased risk (95% CI, 1.5-5.2) of having MetS, independent of other potential confounders. The prevalence of MetS is higher in patients with TRD than in those with other psychiatric disorders and characterized by a considerable undertreatment of some components of MetS in this population. Diagnosis and treatment of the components of MetS should be systematically performed to prevent the occurrence of cardiovascular diseases in patients with TRD. These findings highlight the need for integrated care, with more interaction and coordination between psychiatrists and primary care providers.