Light and Hormones in Seasonal Regulation of Reproduction and Mood

Organisms that inhabit the temperate zone exhibit various seasonal adaptive behaviors, including reproduction, hibernation, molting, and migration. Day length, known as photoperiod, is the most noise-free and widely used environmental cue that enables animals to anticipate the oncoming seasons and adapt their physiologies accordingly. Although less clear, some human traits also exhibit seasonality, such as birthrate, mood, cognitive brain responses, and various diseases. However, the molecular basis for human seasonality is poorly understood. Herein, we first review the underlying mechanisms of seasonal adaptive strategies of animals, including seasonal reproduction and stress responses during the breeding season. We then briefly summarize our recent discovery of signaling pathways involved in the winter depression–like phenotype in medaka fish. We believe that exploring the regulation of seasonal traits in animal models will provide insight into human seasonality and aid in the understanding of human diseases such as seasonal affective disorder (SAD).

Treating winter depressive episodes in bipolar disorder: an open trial of light therapy

Background Light therapy has been used to treat winter depression in bipolar disorder, although the dose, duration, and timing of treatment have differed. The present study is an open trial of light therapy for depressive episodes in autumn/winter using a Dutch protocol specific for patients with a bipolar disorder. Methods Data were collected for the seasons September–April 2017–2018 and September–April 2018–2019. In total, 58 patients received light therapy for a minimum of 7 days and a maximum of 21 days; there was a follow-up measurement after two weeks. Outcomes were quick inventory of depressive symptomatology (QIDS) scores and side effects. Results QIDS scores were significantly lower at the last day of therapy (B = − 6.00, p < 0.001) and 2 weeks after the end of treatment (B = − 6.55, p < 0.001) compared with pre-intervention. Remission (QIDS ≤ 5) was reached in 55% of the treatments and response (50% symptom reduction) in 57% of the treatments. Side effects were mild; two hypomanic periods occurred. Conclusions The Dutch light therapy protocol for patients with a bipolar disorder may be effective in treating a seasonal depression and side effects are mild. Light therapy deserves a prominent place in the treatment because effects may be large and quick.

Seasonal changes in NRF2 antioxidant pathway regulates winter depression-like behavior

Seasonal changes in the environment lead to depression-like behaviors in humans and animals. The underlying mechanisms, however, are unknown. We observed decreased sociability and increased anxiety-like behavior in medaka fish exposed to winter-like conditions. Whole brain metabolomic analysis revealed seasonal changes in 68 metabolites, including neurotransmitters and antioxidants associated with depression. Transcriptome analysis identified 3,306 differentially expressed transcripts, including inflammatory markers, melanopsins, and circadian clock genes. Further analyses revealed seasonal changes in multiple signaling pathways implicated in depression, including the nuclear factor erythroid-derived 2-like 2 (NRF2) antioxidant pathway. A broad-spectrum chemical screen revealed that celastrol (a traditional Chinese medicine) uniquely reversed winter behavior. NRF2 is a celastrol target expressed in the habenula (HB), known to play a critical role in the pathophysiology of depression. Another NRF2 chemical activator phenocopied these effects, and an NRF2 mutant showed decreased sociability. Our study provides important insights into winter depression and offers potential therapeutic targets involving NRF2.

DEPRESSION - TYPES AND TREATMENT OF DEPRESSION

The key symptom of depression is lowering the mood, but this is not the only sign of depression. Depression is a disease in which the symptoms reach various intensities and occur in many configurations. We distinguish the following types of depression: reactive, endogenous, neurotic, anankastic, agitated, large and small, morning (subclinical and subliminal), seasonal, masked, psychotic, postpartum, drug resistant, in children and adolescents, in the elderly, involutional, organic , in bipolar disorder, dysthymia, depression and anxiety, and in somatic diseases. Psychotherapy is now a popular and effective method of treating depression. The effects of treatment after the use of antidepressants appear only after a few weeks from the beginning of therapy. Old-generation medicines: these are tricyclic antidepressants (TLPDs), inhibitors of neuromediator reuptake and monoamine oxidase enzyme (IMAO) inhibitors. The new generation of drugs is distinguished by selective serotonin reuptake inhibitors (SSRIs), selective serotonin and noradrenaline reuptake inhibitors (SNRIs), four-ring drugs, noradrenaline reuptake inhibitors, selective reversible MAO inhibitors, and drugs with other mechanisms of action. Phototherapy (treatment of light) is currently a widely accepted method of winter depression therapy. Other treatments for depression include electroconvulsive therapy and transcranial magnetic stimulation.