The dexamethasone suppression test in seasonal affective disorder

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

At high latitudes, about 10% of the population suffers from depression in winter. Although it has become a serious public health issue, its underlying mechanism remains unknown. Interestingly, animals also show depression-like behavior in winter, and small teleosts have emerged as powerful models for the study of complex brain disorders. Here, we show that medaka exhibit decreased sociability and increased anxiety-like behavior under winter-like conditions. Using metabolomic and transcriptomic analyses, we found changes in multiple signaling pathways involved in depression, including the NRF2 antioxidant pathway. Chemical genomics and targeted mutation of the NRF2 gene revealed that seasonal changes in the NRF2 pathway regulate winter depression-like behavior. This study provides insights into the understanding and treatment of seasonally regulated affective disorders.

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.

Has the sun set for seasonal affective disorder and HPA axis studies? A systematic review and future prospects

OBJECTIVE

Seasonal Affective Disorder (SAD) is a form of cyclic mood disorder that tends to manifest as winter depression. SAD has anecdotally been described as a hypocortisolemic condition. However, there are no systematic reviews on SAD and Hypothalamic-Pituitary-Adrenal (HPA) axis function. This review intends to summarize these findings.

METHODS

Using the PRISMA (2009) guideline recommendations we searched for relevant articles indexed in databases including MEDLINE, EMBASE, PsycINFO, and PsychArticles. The following keywords were used: "Seasonal affective disorder", OR "Winter Depression", OR "Seasonal depression" associated with: "HPA Axis" OR "cortisol" OR "CRH" OR "ACTH".

RESULTS

Thirteen papers were included for qualitative analysis. Studies used both heterogeneous methods and populations. The best evidence comes from a recent study showing that SAD patients tend to demonstrate an attenuated Cortisol Awakening Response (CAR) in winter, but not in summer, compared to controls. Dexamethasone Suppression Test (DST) studies suggest SAD patients have normal suppression of the HPA axis.

CONCLUSION

There is still insufficient evidence to classify SAD as a hypocortisolemic condition when compared to controls. Heterogeneous methods and samples did not allow replication of results. We discuss the limitations of these studies and provide new methods and targets to probe HPA axis function in this population. SAD can provide a unique window of opportunity to study HPA axis in affective disorders, since it is highly predictable and can be followed before, during and after episodes subsides.

Decreased daytime illumination leads to anxiety-like behaviors and HPA axis dysregulation in the diurnal grass rat (Arvicanthis niloticus)

The impact of ambient light on mood and anxiety is best exemplified in seasonal affective disorder, in which patients experience depression and anxiety in winter when there is less light in the environment. However, the brain mechanisms underlying light-dependent changes in affective state remain unclear. Our previous work revealed increased depression-like behaviors in the diurnal Nile grass rat (Arvicanthis niloticus) housed in a dim light-dark (dim-LD) cycle as compared to the controls housed in a bright light-dark (bright-LD) condition. As depression is often comorbid with anxiety and is associated with dysregulation of the body's stress response system, the present study examined the anxiety-like behaviors as well as indicators of the hypothalamic-pituitary-adrenal (HPA) axis functioning in the grass rats. Animals housed in dim-LD showed increased anxiety-like behaviors compared to bright-LD controls, as revealed by fewer entries and less time spent at the center in the open field test and more marbles buried during the marble-burying test. Following the marble-burying test, dim-LD animals showed higher plasma corticosterone (CORT) levels and hippocampal Fos expression. Although the daily CORT rhythm was comparable between bright-LD and dim-LD groups, the day/night variation of corticotropin-releasing hormone mRNA expression in the paraventricular nucleus was diminished in dim-LD animals. In addition, glucocorticoid receptor and mineralocorticoid receptor mRNA expression were higher in the hippocampus of dim-LD animals. The results suggest that in diurnal species, reduced daytime illumination can lead to increased anxiety-like behaviors and altered HPA axis functioning, providing insights into the link between decreased environmental illumination and negative emotion.

Adrenal Clocks and the Role of Adrenal Hormones in the Regulation of Circadian Physiology

The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) and subordinate clocks that disseminate time information to various central and peripheral tissues. While the function of the SCN in circadian rhythm regulation has been extensively studied, we still have limited understanding of how peripheral tissue clock function contributes to the regulation of physiological processes. The adrenal gland plays a special role in this context as adrenal hormones show strong circadian secretion rhythms affecting downstream physiological processes. At the same time, they have been shown to affect clock gene expression in various other tissues, thus mediating systemic entrainment to external zeitgebers and promoting internal circadian alignment. In this review, we discuss the function of circadian clocks in the adrenal gland, how they are reset by the SCN and may further relay time-of-day information to other tissues. Focusing on glucocorticoids, we conclude by outlining the impact of adrenal rhythm disruption on neuropsychiatric, metabolic, immune, and malignant disorders.

Short day lengths alter stress and depressive-like responses, and hippocampal morphology in Siberian hamsters

Many psychological disorders comprise a seasonal component. For instance, seasonal affective disorder (SAD) is characterized by depression during autumn and winter. Because hippocampal atrophy may underlie the symptoms of depression and depressive-like behaviors, one goal of this study was to determine whether short days also induce structural changes in the hippocampus using photoperiod responsive rodents--Siberian hamsters. Exposure to short days increases depressive-like responses (increased immobility in the forced swim test) in hamsters. Male hamsters were housed in either short (LD 8:16) or long days (LD 16:8) for 10 weeks and tested in the forced swim test. Brains were removed and processed for Golgi impregnation. HPA axis function may account for photoperiod-related changes in depressive-like responses. Thus, stress reactivity was assessed in another cohort of photoperiod-manipulated animals. Short days reduced soma size and dendritic complexity in the CA1 region. Photoperiod did not induce gross changes in stress reactivity, but an acute stressor disrupted the typical nocturnal peak in cortisol concentrations. These data reveal that immobility induced by exposure to short days is correlated with reduced CA1 cell complexity (and perhaps connectivity). This study is the first to investigate hippocampal changes in the context of short-day induced immobility and may be relevant for understanding psychological disorders with a seasonal component.

Potential animal models of seasonal affective disorder

Seasonal affective disorder (SAD) is characterized by depressive episodes during winter that are alleviated during summer and by morning bright light treatment. Currently, there is no animal model of SAD. However, it may be possible to use rodents that respond to day length (photoperiod) to understand how photoperiod can shape the brain and behavior in humans. As nights lengthen in the autumn, the duration of the nightly elevation of melatonin increase; seasonally breeding animals use this information to orchestrate seasonal changes in physiology and behavior. SAD may originate from the extended duration of nightly melatonin secretion during fall and winter. These similarities between humans and rodents in melatonin secretion allows for comparisons with rodents that express more depressive-like responses when exposed to short day lengths. For instance, Siberian hamsters, fat sand rats, Nile grass rats, and Wistar rats display a depressive-like phenotype when exposed to short days. Current research in depression and animal models of depression suggests that hippocampal plasticity may underlie the symptoms of depression and depressive-like behaviors, respectively. It is also possible that day length induces structural changes in human brains. Many seasonally breeding rodents undergo changes in whole brain and hippocampal volume in short days. Based on strict validity criteria, there is no animal model of SAD, but rodents that respond to reduced day lengths may be useful to approximate the neurobiological phenomena that occur in people with SAD, leading to greater understanding of the etiology of the disorder as well as novel therapeutic interventions.

Pituitary volume and the effects of phototherapy in patients with seasonal winter depression: a controlled study

OBJECTIVES: Our aims were to investigate the pituitary volume in patients with seasonal winter depression and healthy volunteers in winter and summer, and to assess the effects of phototherapy in these patients. METHOD: The pituitary volume of 12 patients with winter depression and 12 healthy controls, paired according gender, age and menstrual cycle, were obtained from magnetic resonance imaging in winter and summer. Eight patients were submitted to phototherapy (10000 vs. 2500 lux) in a double-blind crossover fashion during the winter, and reassessed (symptoms and magnetic resonance imaging) after treatment. RESULTS: There were no significant differences in pituitary volume between controls and patients in winter or summer. Exposure to phototherapy (10000 lux) decreased the depressive symptoms (p = 0.004), but the glandular volume did not change (p = 0.5). However, the pituitary volume in winter showed a positive correlation with the severity of depression in these patients (r = 0.69, p = 0.04). CONCLUSIONS: The results suggest that neither winter depression nor the change of seasons is associated with significant change in the pituitary volume. Despite the fact that this study was performed in a tropical area, phototherapy with 10000 lux showed to be an efficient treatment in this SAD patients sample.

Affective and adrenocorticotrophic responses to photoperiod in Wistar rats

The present study tested the hypothesis that seasonal intervals of exposure to modest changes in photoperiod, typical of those experienced by humans living in temperate latitudes (10-14 h light/day), engage changes in emotional behaviour of Wistar rats, a commonly-used animal model for investigations of affective physiology. Short day lengths (<or= 12 h light/day) induced behavioural despair in a forced-swim test, exploratory anxiety in an open field arena, and anhedonia in a two-bottle sucrose preference task, relative to longer day lengths. Plasma adrenocorticotrophic hormone was lower in short-day relative to long-day rats, but testosterone and corticosterone concentrations were comparable across treatments. In common with animals that engage reproductive responses to day length, reproductively nonresponsive mammals such as Wistar rats exhibit changes in affective state following small changes in day length. Wistar rats may provide an animal model for the study of seasonal mood regulation because the neuroendocrine, depressive, anxious and anhedonic responses of Wistar rats to short days bear similarities to those observed in some human populations. Standard laboratory husbandry practices (exposure to a 12 : 12 h light/dark cycle) may inadvertently deliver a chronic background depressive and anxiogenic stimulus.

Higher cortisol levels in spring and fall in patients with major depression

BACKGROUND

Multiple lines of evidence suggest that there are seasonal effects on mood and behavior, and that these effects are related to serotonergic and hypothalamic-pituitary-adrenal (HPA) function. This study sought to determine whether there is a seasonal effect on clinical parameters, baseline cortisol and prolactin levels, and cortisol and prolactin responses to fenfluramine administration in subjects with major depression.

METHODS

In all, 136 subjects with major depression entered the study. Sixty-two subjects who had a major depressive episode (MDE) in Spring or in Fall (the Spring/Fall group) were compared to 74 subjects who had MDE in Winter or in Summer (the Winter/Summer group). Demographic and clinical parameters were assessed and recorded. Clinical parameters included depression, aggression, impulsivity, hopelessness, hostility, and current suicide ideation rating scales, suicide attempt status, and number and maximum lethality of suicide attempts. Cortisol and prolactin levels were drawn before fenfluramine administration and hourly for 5 h thereafter. Cortisol and prolactin levels were computed as the area under the curve of hourly cortisol measurements.

RESULTS

Baseline cortisol levels were significantly higher in the Spring/Fall group compared to the Winter/Summer group (14.1+/-4.5 ng/ml vs. 12.5+/-4.4 ng/ml, df=132, t=2.16, p=0.03). There were no seasonal effects on baseline prolactin levels, or post-challenge cortisol and prolactin levels.

CONCLUSIONS

The Spring/Fall group and the Winter/Summer group may represent different subtypes of major depression. Future studies need to both confirm our results and elucidate the mechanism of the circannual effect on biological function in depressed patients. The results of our study underline the importance of considering seasonality in psychobiology.

A case of seasonal bipolar disorder exacerbated by Cushing's disease

While depression is common in Cushing's syndrome from whatever cause (pituitary, adrenal, or ectopic adrenocorticotropic hormone-secreting tumor or hyperplasia, or exogenous administration of glucocorticoids) and hypercortisolemia is prevalent in major depression, any association between seasonal affective disorder and Cushing's syndrome is unknown. We present a case of seasonal bipolar disorder, gradually worsening for more than 9 years (1985-1994), accompanied by increasing osteoporosis, mild weight gain, and slight truncal obesity in a middle-aged woman. In January 1991, her seasonal affective disorder was successfully treated with light therapy, but in the following year, bipolar mood swings with a seasonal pattern emerged, which were refractory to light therapy and antidepressants but responsive to lithium. In August 1992, she became depressed despite a 1500-mg lithium daily dosage along with light therapy, and, in 1993, a diagnosis of Cushing's disease (Cushing's syndrome as a result of a pituitary adrenocorticotropic hormone-secreting tumor) was made. The pituitary tumor was removed in February 1994, and pituitary function was fully restored by 1996. While the symptoms of Cushing's syndrome subsided, her bipolar illness continued to require maintenance treatment with low doses of lithium but did not require light therapy.

Does neuroimmune dysfunction mediate seasonal mood changes in winter depression?

BACKGROUND

Animal studies have demonstrated seasonal changes in immune function mediated by nocturnal melatonin duration as a biological signal for photoperiod. Recent research has highlighted the potential role of neuroimmune dysfunction in depressive disorders. The etiology of winter depression (seasonal affective disorder, or SAD) is not known, but a number of studies have provided support for both photoperiod and neurotransmitter hypotheses.

HYPOTHESIS

A new hypothesis is presented that links the SAD data on melatonin, photoperiod, and neurotransmitters by proposing that seasonal increases in proinflammatory cytokines are critical in the pathophysiology of winter SAD.

TESTING THE HYPOTHESIS

In SAD patients, but not healthy subjects: proinflammatory cytokines will be increased and the Th1/Th2 balance will be shifted to the left in winter compared to summer; neuroimmune function will be correlated with nocturnal melatonin duration in SAD patients; and light treatment will correct neuroimmune dysfunction.

IMPLICATIONS OF THE HYPOTHESIS

Diagnostic tests for SAD may be developed using cytokine assays; neuroimmune dysfunction may be predictors of response to treatments; new treatments for SAD (immune or anti-inflammatory treatment) may be developed.

Cortisol in light treatment of seasonal and non-seasonal depression: relationship between melatonin and cortisol

The effect of bright light on cortisol and the relationship between melatonin and cortisol were studied in 63 depressed patients (42 patients with a seasonal pattern and 21 patients with a non-seasonal pattern). The patients were matched for age, time of treatment and severity of depression. Before and after light treatment the severity of the depression was rated with the Comprehensive Psychopathological Rating Scale (23 items) and the Hamilton Depression Rating scale (18 items), and serum cortisol and melatonin were drawn at nine time-points between 20.00 and 08.00 hours. Two hours of light treatment (350 cd m-2) was given daily for 10 days either in the morning (06.00-08.00 hours) or in the evening (18.00-20.00 hours). As reported earlier, patients with a seasonal pattern improved significantly more than patients with a non-seasonal pattern of depression, and no significant differences were found between the treatment efficacy of morning compared to evening light. A cosinor analysis showed that the cortisol batyphase was significantly advanced by morning light, but was not delayed by evening light. A delay in batyphase cortisol showed a weak significant correlation with a decrease in the absolute and relative sum of scores. The batyphase of cortisol occurred approximately 3 h earlier than the acrophase of melatonin. Of the changes in the melatonin acrophase 43% were reflected in a change of cortisol batyphase, indicating a hierarchical relationship with melatonin as the co-ordinating hormone transducing part of the information of the external light to the phase position of cortisol. No significant differences between patients with a seasonal or a non-seasonal pattern were seen in mesor, amplitude or batyphase of cortisol before treatment, and no significant changes in mesor or amplitude were seen as a result of light treatment.

Circadian temperature and cortisol rhythms during a constant routine are phase-delayed in hypersomnic winter depression

Circadian temperature, cortisol, and thyroid-stimulating hormone (TSH) rhythms during a constant routine were assessed in 6 female controls and 6 female patients with hypersomnic winter depression (seasonal affective disorder, SAD) before and after morning bright light treatment. After sleep was standardized for 6 days, the subjects were sleep-deprived and at bed rest for 27 hours while rectal temperature, cortisol, and TSH levels were assessed. The minimum of the fitted rectal temperature rhythm was phase-delayed in the SAD group compared to the controls 5:42 AM vs. 3:16 AM (p < .005); with bright light treatment, the minimum advanced from 5:42 AM to 3:36 AM (p = .06). The minimum of the cortisol rhythm was phase-delayed in the SAD group compared to the control group, 12:11 AM vs. 10:03 PM (P < .05); with bright light treatment, the minimum advanced from 12:11 AM to 10:38 PM (P = .06) [corrected]. The acrophase of the TSH rhythm was not significantly phase-delayed in SAD subjects compared to control, though the trend appeared to be toward a phase-delay (p = .07). After bright light therapy, the TSH acrophase was not significantly different in the SAD subjects; the trend was a phase-advance (p = .09). Overall, the data suggest that circadian rhythms are phase-delayed relative to sleep in SAD patients and that morning bright light phase-advances those rhythms.

Circadian rhythms and the pharmacology of affective illness

The chronic effects of antidepressant drugs (ADs) on circadian rhythms of behavior, physiology and endocrinology are reviewed. The timekeeping properties of several classes of ADs, including tricyclic antidepressants, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, serotonin agonists and antagonists, benzodiazepines, and melatonin are reviewed. Pharmacological effects on the circadian amplitude and phase, as well as effects on day-night measurements of motor activity, sleep-wake, body temperature (Tb), 3-methoxy-4-hydroxyphenylglycol, cortisol, thyroid hormone, prolactin, growth hormone and melatonin are examined. ADs often lower nocturnal Tb and affect the homeostatic regulation of sleep. ADs often advance the timing and decrease the amount of slow wave sleep, reduce rapid eye movement sleep and increase or decrease arousal. Together, AD effects on nocturnal Tb and sleep may be related to their therapeutic properties. ADs sometimes delay nocturnal cortisol timing and increase nocturnal melatonin, thyroid hormone and prolactin levels; these effects often vary with diagnosis, and clinical state. The effects of ADs on the coupling of the central circadian pacemaker to photic and nonphotic zeitgebers are discussed.

Changes in norepinephrine output following light therapy for fall/winter seasonal depression

Recurrent fall/winter depressions that remit during spring and summer have been called Seasonal Affective Disorders (SAD) (Wehr and Rosenthal 1989). The pathophysiology of SAD, its relationship to nonseasonal affective disorders, and the mechanism of action of light therapy, which is effective in treating SAD, remain to be elucidated (Depue et al 1989; Jacobsen et al 1987; James et al 1986; Joseph-Vanderpool et al 1991; Skwerer et al 1988, Terman et al 1989). Norepinephrine (NE) may play a role in the mechanisms of action of many antidepressant treatments (Schildkraut 1965) that alter NE metabolism (Schildkraut et al 1964 and 1965) and decrease the urinary output of NE and its metabolites, i.e., "whole-body NE turnover" (WBNET) (Golden et al 1988; Potter et al 1988). The present study explored whether light therapy also reduces the urinary output of NE and its metabolites.

Seasonal affective disorder, Part II: Phototherapy, an expanded role of the psychosocial nurse

The integration of neurobiology into the research and practice of psychosocial nursing is an imperative for the decade of the 1990s. This substantial goal probably will be achieved through the completion of smaller endeavors. This article is intended to be one such contribution. The purpose of this article are threefold. First, it will introduce the psychosocial nurse to the characteristics of Seasonal Affective Disorder (SAD). This article also will provide the psychosocial nurse with the putative biological basis of SAD and phototherapy. Finally, specific information regarding the therapeutic application of bright light is provided.

Is winter depression a bipolar disorder?

Sixty-one winter depressive patients were evaluated for evidence of bipolar illness. Using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version and the General Behavior Inventory, only nine (15%) could be considered bipolar. On prospective evaluation of patients during the summer following winter depression, few showed signs of manic or hypomanic symptoms. Also, few patients had a family history of bipolar illness. When patients were asked to evaluate symptoms of winter depression, lack of energy was found to be the most prominent feature of the syndrome.

Geophysical variables and behavior: LVII. Seasonal affective disorder and phototherapy

Seasonal affective disorder, depressive symptoms that recur in fall and winter and abate in spring-summer, for many patients in the United States and Europe, have been alleviated by exposure to bright, full spectrum light for several hours daily (phototherapy). The characteristics of these patients, the procedures used, the theoretical explanations of the mechanisms, and the potential of phototherapy are reviewed.

Phototherapy for depressive disorders: a review

The use of bright light (phototherapy) for psychiatric disorders has recently generated much interest among researchers and the lay population. The authors review the treatment studies of phototherapy for seasonal and non-seasonal depressive disorders, and the empirical evidence for theories of the psychophysiology of phototherapy. Although its mechanism of action remains to be explained, phototherapy appears to be a safe and effective treatment for seasonal depression and a promising treatment for non-seasonal depression. Further questions and future research directions are presented.

Cortisol measures in primary major depressive disorder with hypersomnia or appetite increase

Morning plasma cortisol response to the 1 mg dexamethasone suppression test along with cortisol levels in blood, cerebrospinal fluid (CSF), and urine were measured in hospitalized male and female patients with primary major depressive disorder who reported hypersomnia (n = 23), or increase in appetite (n = 22). Comparisons were drawn to cortisol levels in patients with primary major depressive disorder who did not report hypersomnia or appetite increase (n = 23) and to normal controls (n = 23), all age- and sex-matched. Depressives with hypersomnia or increased appetite showed higher than normal 24-h urinary free cortisol concentrations. Depressed patients without hypersomnia or appetite increase had in addition to elevated free urinary cortisol concentrations higher than normal morning plasma cortisol levels before and after dexamethasone administration and a higher incidence of cortisol non-suppression after dexamethasone compared to normal subjects. The findings provide preliminary evidence that HPA activation in depression is diminished in the presence of hypersomnia and/or an increased appetite. Studies of the hypothalamic-pituitary-adrenal axis may be useful for differentiating subtypes of depression characterized by hypersomnia or enhanced appetite.