The presence or absence of light during flotation restricted environmental stimulation: Effects on plasma cortisol,blood pressure,and mood

This study examined the effect of light on relaxation associated with flotation restricted environmental stimulation therapy (REST), as measured by plasma cortisol, mean arterial pressure, and psychometric parameters. Twenty-one subjects were paired by baseline cortisol levels into two groups: one experiencing flotation REST in the presence of light (REST-L) and one experiencing flotation REST in the absence of light (REST-D). Subjects were 15 male and 6 female students aged 22–28 in normal health who had not experienced REST. Repeated flotation REST (8 sessions) either with light or without light was associated with a decrease in plasma cortisol and a decrease in mean arterial pressure, with no differences in effectiveness between groups. The psychometric assessment of mood, using the POMS scale, before and after sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D groups. These data suggest that the presence of light did not compromise the flotation REST experience, as evidenced by the lack of difference between REST-L and REST-D groups.     

Restricting environmental stimulation influences levels and variability of plasma cortisol

Restricting stimulation from the environment has been shown to alter psychological and physiological states. The present study of 27 healthy subjects examines the effects of restricted environmental stimulation technique (REST) on plasma levels of cortisol and variability in plasma cortisol levels across repeated REST sessions. The REST environment consisted of a 1.2 X 1.2 X 2.4-m ovoid chamber containing 25 cm of saturated MgSO4 solution (sp gr 1.28) maintained at 34.5 degrees F. The buoyant supinely floating subject experienced a minimum of light, sound, and temperature awareness and spatial orientation. The non-REST environment was a cushioned reclining chair in a quiet dimly lit room. The 5-wk protocol consisted of four visits for blood sampling during a 2-wk baseline followed by eight REST or non-REST sessions, 40 min each, with blood samples taken on four nonsession days between sessions 5 and 8. Variability in plasma cortisol was expressed in terms of standard deviation. REST was associated with across-session decreases of 21.6% in plasma cortisol and 50.5% in plasma cortisol variability, whereas no changes in these measures occurred in non-REST. It is concluded that REST influences both static and dynamic aspects of adrenocortical function, possibly altering the feedback monitoring of plasma cortisol.     

Effects of relaxation associated with brief restricted environmental stimulation therapy (REST) on plasma cortisol,ACTH, and LH

Restricted Environmental Stimulation Therapy (REST), which involves placing an individual into an environment of severely reduced stimulation for brief periods, has been subjectively reported to produce deep relaxation. The present study determines the effects of REST-assisted relaxation on plasma cortisol, ACTH, and luteinizing hormone (LH). These parameters were also measured in a group exposed to a similar relaxation paradigm, but without REST (non-REST). Each subject experienced two baseline sessions (1 and 2), four REST (or non-REST) relaxation sessions (3, 4, 5, 6), and two follow-up sessions (7 and 8). Pre- and postsession plasma hormone levels were measured in sessions 1, 2, 5, and 8. Both REST and non-REST subjects reported that the experience was relaxing. During the treatment period (session 5) pre- to postsession changes in cortisol and ACTH, but not in LH, were significantly greater for the REST group than for the non-REST group. Plasma cortisol level also decreased across sessions in the REST group, with levels in sessions 5 and 8 significantly lower than the baseline (sessions 1 and 2). Non-Rest subjects showed no change in plasma cortisol across sessions. No significant change in plasma ACTH or LH occurred across sessions in the REST or non-REST groups, although ACTH showed a decreasing trend. These data demonstrate that repeated brief REST-assisted relaxation produces a relaxation state associated with specific decreases in pituitary-adrenal axis activity.     

Biochemical changes associated with thermal biofeedback treatment of hypertension

Fifty-two hypertensive patients whose blood pressure (BP) was controlled on two medications received either 16 sessions of thermal biofeedback (n = 30) for hand warming or 8 sessions of progressive muscle relaxation (n = 22) prior to medication withdrawal. A number of biochemical measures, including plasma norepinephrine (NEPI) (supine and standing), plasma renin activity, plasma aldosterone, and urinary sodium and potassium, were taken before treatment and after treatment while medication remained constant. Results for the biofeedback-treated patients showed significant reductions in mean arterial pressure as well as in both supine and standing NEPI, while the other biochemical measures were unchanged. There were no significant changes on any variable for the relaxation-treated patients. Although the group data support a reduction in peripheral sympathetic tone as associated with the decrease in BP for the thermal biofeedback condition, dose-response relations were not significant.     

Cardiovascular and adrenaline-releasing effects of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin in streptozotocin diabetic rats.

The 5-hydroxytryptamine1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) has been reported to trigger sympathoinhibition, as evidenced by its cardiovascular effects, and adrenal catecholamine secretion. The purpose of this study was to analyze the cardiovascular and adrenaline-releasing effects of 8-OH-DPAT in 1 week streptozotocin diabetic rats. 8-OH-DPAT-induced changes in mean arterial pressure (MAP) and heart rate (HR) were determined directly in anesthetized rats, whilst changes in plasma adrenaline (and plasma corticosterone and glucose) levels were analyzed in conscious rats. Resting blood pressure and heart rate were diminished in diabetics, when compared with controls. These changes were associated with a decrease in body weight and a marked increase in resting plasma glucose levels. Diabetes did not affect MAP response to 8-OH-DPAT, except for a decrease in the amplitude of MAP maximal fall, which was associated with a diminished bradycardic response to 8-OH-DPAT. Blood pressure response to prazosin (0.5 mg/kg) in 8-OH-DPAT-pretreated rats was also diminished in diabetics. Lastly, diabetes prevented the adrenaline-releasing and hyperglycemic effects of 8-OH-DPAT (250 ug/kg).     

Diurnal rhythms of plasma growth hormone,somatostatin, thyroid hormones,cortisol and glucose concentrations in rainbow trout,Oncorhynchus mykiss,during progressive food deprivation

Abstract

The diurnal patterns of changes in plasma cortisol, growth hormone (GH), somatostatin‐14 (SRIF), thyroid hormones (L‐thyroxine, T₄ and triiodo‐L‐thyronine, T₃) and glucose were investigated in rainbow trout, Oncorhynchus mykiss, both during single meal‐feeding and during a progressive fast of 13 weeks. All measured variables exhibited a diurnal pattern in fed rainbow trout, most of which appeared to be correlated with the time of feeding (30–60 min after the onset of light), while additional changes, associated with the scotophase were also found for cortisol. Although fasting had no affect on mean daily plasma cortisol or SRIF concentrations, there was a progressive increase in mean daily plasma GH concentrations and a progressive decrease in mean daily plasma thyroid hormone and glucose concentrations associated with fasting. However, for GH, significant changes were not evident until week 10 of the fast. In addition, fasting appeared to phase‐shift the diurnal patterns of plasma GH, cortisol and glucose concentrations; the consequence of such a shift is that conclusions as to the effects of fasting, if based on a single time of sampling, may be flawed.     

Chronic alterations in ovine maternal corticosteroid levels influence uterine blood flow and placental and fetal growth

Previous work from this laboratory demonstrated that the elevation of maternal plasma corticosteroid concentrations during pregnancy is important for the support of fetal development. Reducing ovine maternal plasma cortisol concentrations to nonpregnant levels stimulates homeostatic responses that defend fetal blood volume. The present study was designed to test the hypothesis that chronic decreases or increases in maternal plasma cortisol concentration alter uterine and placental blood flow and morphology. Three groups of pregnant ewes and their fetuses were chronically catheterized and studied: ewes infused with cortisol (1 mg.kg(-1).day(-1); high cortisol), ewes adrenalectomized and underreplaced with cortisol (0.5 mg.kg(-1).day(-1); low cortisol), and control ewes. The normal increment in uterine blood flow between 120 and 130 days was eliminated in the low-cortisol ewes; conversely, uterine blood flow was increased in the high-cortisol group compared with the control group. Fetal arterial blood pressure was increased in the high-cortisol group compared with controls, but there was no increase in fetal arterial pressure from 120 to 130 days of gestation in the low-cortisol group. The fetuses of both low-cortisol and high-cortisol groups had altered placental morphology, with increased proportions of type B placentomes, and overall reduced fetal placental blood flow. The rate of fetal somatic growth was impaired in both low-cortisol and high-cortisol groups compared with the fetuses in the intact group. The results of this study demonstrate that maternal plasma cortisol during pregnancy is an important contributor to the maternal environment supporting optimal conditions for fetal homeostasis and somatic growth.     

Biochemical changes associated with thermal biofeedback treatment of hypertension

Fifty-two hypertensive patients whose blood pressure (BP) was controlled on two medications received either 16 sessions of thermal biofeedback (n=30) for hand warming or 8 sessions of progressive muscle relaxation (n=22) prior to medication withdrawal. A number of biochemical measures, including plasma norepinephrine (NEPI) (supine and standing), plasma renin activity, plasma aldosterone, and urinary sodium and potassium, were taken before treatment and after treatment while medication remained constant. Results for the biofeedback-treated patients showed significant reductions in mean arterial pressure as well as in both supine and standing NEPI, while the other biochemical measures were unchanged. There were no significant changes on any variable for the relaxation-treated patients. Although the group data support a reduction in peripheral sympathetic tone as associated with the decrease in BP for the thermal biofeedback condition, dose-response relations were not significant.This research was supported by a grant from NHLBI, HL-27622.     

Exploring Shamanic Journeying: Repetitive Drumming with Shamanic Instructions Induces Specific Subjective Experiences but No Larger Cortisol Decrease than Instrumental Meditation Music

Exposure to repetitive drumming combined with instructions for shamanic journeying has been associated with physiological and therapeutic effects, such as an increase in salivary immunoglobulin A. In order to assess whether the combination of repetitive drumming and shamanic instructions is specifically associated with these effects, we compared the effect of listening to either repetitive drumming or instrumental meditation music for 15 minutes on salivary cortisol concentration and on self-reported physiological and psychological states. For each musical style, two groups of participants were exposed to two conditions: instructions for shamanic journeying or relaxation instructions. A total of 39 participants (24 females) inexperienced in shamanic journeying completed the experiment. Salivary cortisol concentrations were measured before and after exposure to music. In addition, participants filled out a mood questionnaire before and after the experiment and completed a post experiment questionnaire on their experiences. A significant decrease in the concentration in salivary cortisol was observed across all musical styles and instructions, indicating that exposure to 15 minutes of either repetitive drumming or instrumental meditation music, while lying down, was sufficient to induce a decrease in cortisol levels. However, no differences were observed across conditions. Significant differences in reported emotional states and subjective experiences were observed between the groups. Notably, participants exposed to repetitive drumming combined with shamanic instructions reported experiencing heaviness, decreased heart rate, and dreamlike experiences significantly more often than participants exposed to repetitive drumming combined with relaxation instructions. Our findings suggest that the subjective effects specifically attributed to repetitive drumming and shamanic journeying may not be reflected in differential endocrine responses.     

Influences of photoperiod and alternate days of feeding on plasma growth hormone and thyroid hormone levels in juvenile rainbow trout

The diurnal patterns of plasma growth hormone (GH), thyroid hormone and cortisol concentrations in rainbow trout Oncorhynchus mykiss held under three photoperiod (L : D) regimes (6 : 18, 12 : 12 and 18 : 6), and fed either daily (DF) or on alternate days (ADF) with 2·0% body mass per day of a commercial trout diet were determined. The ADF groups had reduced total mass gain and specific growth rates compared with DF fish, but photoperiod had no affect on growth for either of the feeding regime groups. In the ADF groups, the mean 24 h plasma thyroxine (T₄) and triiodothyronine (T₃) concentrations were significantly lower, both on days of feeding and days of fasting, than in DF fish held under all three photoperiod regimes, but for GH, only the 18L : 6D DF group was higher than the comparable ADF groups. There were no significant differences in mean 24 h plasma cortisol concentrations of DF and ADF groups. Diurnal patterns of plasma GH, cortisol, T₄ and T₃ were found in DF fish held under all three photoperiod regimes. Increases in plasma cortisol changes were associated with the onset of the light phase; elevations in plasma GH and T₄ concentrations were more closely associated with clock time, regardless of photoperiod; increases in plasma T₃ concentrations were strongly associated with time of feeding. In ADF groups, these diurnal changes in plasma GH, T₄ and T₃ concentrations were suppressed for both the fed and fast days, and plasma cortisol concentrations were suppressed on the fasting day. The observations are discussed in terms of the proposed anabolic, catabolic and growth regulating roles of these hormones in different growth and metabolic modifying situations in teleosts.     

The effects of acid and acid/aluminum exposure on circulating plasma cortisol levels and other blood parameters in the rainbow trout, Salmo gairdneri

Softwater (Ca²⁺=50, Na⁺= 50(μequiv. l⁻¹) acclimated rainbow trout were fitted with chronic arterial catheters to allow for repetitive blood sampling. After 48 h recovery they were then exposed to either control (pH 6.5, Al = 0μg l⁻¹), acid (pH 4.8, Al = 0μg l⁻¹) or acid plus aluminum (pH 4.8, A1 = 112 μg l⁻¹) conditions for 72 h. Parameters measured included blood glucose, lactate, haemoglobin, haematocrit and plasma Na⁺, Cl⁻, protein and cortisol.
Exposure to pH 4'8 alone caused no mortality, a moderate ionoregulatory disturbance and a transient elevation in plasma cortisol. All other parameters were not significantly different from controls. Addition of aluminum to this exposure caused 100% mortality with a mean survival time of only 27.0 h. There was a marked decrease in plasma ions, hyperglycemia, lactate accumulation, haemoconcentration, red cell swelling, and a sharp rise in plasma cortisol becoming greatly increased as the fish neared death. The mechanism of toxicity of acute acid/aluminum exposure, the role for cortisol under such conditions, and the validity of cortisol and glucose as indicators of stress in fish are discussed.     

Antepartum Depression Severity is Increased During Seasonally Longer Nights: Relationship to Melatonin and Cortisol Timing and Quantity

Current research suggests that mood varies from season to season in some individuals, in conjunction with light-modulated alterations in chronobiologic indices such as melatonin and cortisol. The primary aim of this study was to evaluate the effects of seasonal variations in darkness on mood in depressed antepartum women, and to determine the relationship of seasonal mood variations to contemporaneous blood melatonin and cortisol measures; a secondary aim was to evaluate the influence of seasonal factors on measures of melancholic versus atypical depressive symptoms. We obtained measures of mood and overnight concentrations of plasma melatonin and serum cortisol in 19 depressed patients (DP) and 12 healthy control (HC) antepartum women, during on-going seasonal variations in daylight/darkness, in a cross-sectional design. Analyses of variance showed that in DP, but not HC, Hamilton Depression Rating Scale (HRSD) scores were significantly higher in women tested during seasonally longer versus shorter nights. This exacerbation of depressive symptoms occurred when the dim light melatonin onset, the melatonin synthesis offset, and the time of maximum cortisol secretion (acrophase) were phase-advanced (temporally shifted earlier), and melatonin quantity was reduced, in DP but not HC. Serum cortisol increased across gestational weeks in both the HC and DP groups, which did not differ significantly in cortisol concentration. Nevertheless, serum cortisol concentration correlated positively with HRSD score in DP but not HC; notably, HC showed neither significant mood changes nor altered melatonin and cortisol timing or quantity in association with seasonal variations. These findings suggest that depression severity during pregnancy may become elevated in association with seasonally related phase advances in melatonin and cortisol timing and reduced melatonin quantity that occur in DP, but not HC. Thus, women who experience antepartum depression may be more susceptible than their nondepressed counterparts to phase alterations in melatonin and cortisol timing during seasonally longer nights. Interventions that phase delay melatonin and/or cortisol timing—for example, increased exposure to bright evening light—might serve as an effective intervention for antepartum depressions whose severity is increased during seasonally longer nights.     

Effect of acutely-induced lactic acidemia on fetal breathing movements, heart rate, blood pressure, ACTH and cortisol in sheep.

Experiments were conducted in 8 chronically-catheterized fetal sheep at 125-135 days gestation in order to determine the effect of exogenously administered lactic acid to the fetus on fetal heart rate, blood pressure, breathing movements (FBM), electrocortical activity (ECOG), plasma immunoreactive (IR-ACTH) and cortisol concentrations. When fetal arterial pH decreased from 7.37 +/- 0.01 during the control period to 7.20 +/- 0.01, there was an initial bradycardia followed by tachycardia but no change in blood pressure. The amplitude of FBM increased 2-fold initially in association with an increase in PCO2 from 47.9 +/- 2.1 mmHg to 58.8 +/- 3.6 mmHg at 5 min into the lactate infusion. There was no change in the incidence of FBM or low-voltage ECOG and there was no change in the plasma concentrations of IR-ACTH and cortisol with the infusion of lactate. We conclude that the major effects of acutely elevating circulatory lactate concentrations in fetal sheep are to increase the amplitude of FBM and to cause an initial bradycardia followed by a tachycardia.     

The influence of three unchanging photoperiods on growth and parr-smolt transformation in Atlantic salmon, Salmo salar L.

Groups of pre-smolt Atlantic salmon were reared under three experimental photoperiods. Growth rate was significantly enhanced under 24 h of light: 0 h of darkness per diem (24 L: 0 D) compared with 16 L: 8 D and 8 L: 16 D from early January to early May. From the beginning of May until the termination of the experiment on 27 May, growth rate was highest under 8 L: 16 D.
All groups developed bimodal length-frequency distributions during the experiment. The proportion of the population in each of the two growth modes was significantly affected by photoperiod treatment.
The level of plasma cortisol increased significantly from February to May. There were no differences in levels of plasma cortisol among photoperiod treatments.
Judged by development in plasma cortisol, changes in condition factor and external appearance, the parr-smolt transformation was not completed under any of the experimental photoperiods.     

Hormonal mechanisms in the regulation of arterial pressure and its hemodynamic structure in old age

Age-related increase of vascular resistance determines blood pressure (BP) level in normotensive and hypertensive people. Maintenance of normotension in old age is connected with a decrease of the cardiac output. Increased cardiac output is considered to be an important factor of arterial hypertension in old age. Disturbances in renin-angiotensin-aldosterone and hypophyseal-adrenal systems are observed with advanced age and their degree increases in arterial hypertension. Variability of BP within normal range is closely connected with plasma aldosterone and cortisol concentrations. BP level and increased cardiac output are related to increased plasma ACTH and vasopressin concentrations in hypertensive subjects.     

IL-6 enhances plasma IL-1ra,IL-10, and cortisol in humans

The purpose of the present study was to test the hypothesis that a transient increase in plasma IL-6 induces an anti-inflammatory environment in humans. Therefore, young healthy volunteers received a low dose of recombinant human (rh)IL-6 or saline for 3 h. Plasma IL-6 levels during rhIL-6 infusion were approximately 140 pg/ml, corresponding to the levels obtained during strenuous exercise. The infusion of rhIL-6 did not induce enhanced levels of the proinflammatory cytokine TNF-alpha but enhanced the plasma levels of the two anti-inflammatory cytokines IL-1 receptor agonist (IL-1ra) and IL-10 compared with saline infusion. In addition, C-reactive protein increased 3 h post-rhIL-6 infusion and was further elevated 16 h later compared with saline infusion. rhIL-6 induced increased levels of plasma cortisol and, consequently, an increase in circulating neutrophils and a decrease in the lymphocyte number without effects on plasma epinephrine, body temperature, mean arterial pressure, or heart rate. In conclusion, this study demonstrates that physiological concentrations of IL-6 induce an anti-inflammatory rather than an inflammatory response in humans and that IL-6, independently of TNF-alpha, enhances the levels not only of IL-1ra but also of IL-10. Furthermore, IL-6 induces an increase in cortisol and, consequently, in neutrocytosis and late lymphopenia to the same magnitude and with the same kinetics as during exercise, suggesting that muscle-derived IL-6 has a central role in exercise-induced leukocyte trafficking.     

Influence of yohimbine on release of anterior pituitary hormones

We used a double-blind crossover design to study the effects of alpha 2 adrenoreceptor blockade with yohimbine on levels of anterior pituitary hormones. A dose of yohimbine was used which raised plasma norepinephrine from 379 +/- 74 (S.E.) to 730 +/- 143 pg/ml and mean arterial pressure from 83 +/- 4 to 92 +/- 5 torr (p less than 0.025). This dose (125 micrograms/kg, then 1 microgram/kg/min) also altered mood when compared to saline infusion. In spite of these changes, when prolactin, cortisol, ACTH, beta-endorphin, TSH and growth hormone were measured after 45 minutes of yohimbine infusion, no changes from baseline were noted. These data suggest that in normal man, at rest, alpha 2 adrenoreceptors in the hypothalamus, adenohypophysis or other brain areas do not tonically modulate release of these hormones into the blood.     

ADRENAL FUNCTION IN WILD AND REHABILITATED PACIFIC HARBOR SEALS (PHOCA VITULINA RICHARDII) AND IN SEALS WITH PHOCINE HERPESVIRUS-ASSOCIATED ADRENAL NECROSIS

Adrenal function in harbor seals (Phoca vitulina richardii) was evaluated using adrenocorticotrophic hormone (ACTH) stimulation tests and fecal cortisol levels. The effect of ACTH administration on plasma cortisol and aldosterone levels in five free-living and 14 rehabilitated harbor seal pups was determined using enzyme immunoassay and radioimmunoassay, respectively. In free-living seals, injection of ACTH caused a significant increase in mean plasma cortisol but not of mean aldosterone levels 60 min postinjection. In these seals, mean initial plasma aldosterone was significantly higher than initial levels in rehabilitated seals, while initial cortisol levels were similar. Of the rehabilitated seals, eight died with adrenal cortical necrosis associated with herpesvirus inclusions, while six lived to be released. In the seals that were released, both mean initial cortisol levels and response to ACTH decreased through rehabilitation. In the seals that died, mean initial cortisol and response to ACTH increased through rehabilitation. The differences between initial cortisol levels in seals that lived and those that died were significant at weeks two and four of rehabilitation but not at the week of admission. There was considerable individual variation in initial plasma aldosterone levels and responses to ACTH, although initial aldosterone levels were significantly higher in rehabilitated seals that died than in seals that lived. Seals with adrenal necrosis associated with herpesvirus infection did not have decreased adrenal hormone responses to ACTH. Differences between initial hormone levels and responses to ACTH in different groups of seals may be associated with differing stress levels. Fecal cortisol assays were not a useful method of assessing adrenal function in these seals, as measured levels did not correlate with plasma cortisol levels.     

Maternity blues and major endocrine changes: Cardiff puerperal mood and hormone study II.

OBJECTIVES--To define relation between mood and concentrations of progesterone and cortisol during perinatal period to test hypothesis that rapid physiological withdrawal of steroid hormones after delivery is associated with depression. DESIGN--Prospective study of primiparous women from two weeks before expected date of delivery to 35 days postpartum. SETTING--Antenatal clinic in university hospital, obstetric inpatient unit, patients'' homes. SUBJECTS--120 of 156 primiparous women interviewed. Remainder excluded because of major marital, socioeconomic, or medical problems or because caesarean section required. MAIN OUTCOME MEASURES--Concentrations of progesterone and cortisol in saliva samples; women''s moods assessed by various scores for depression. RESULTS--Changes in salivary progesterone and cortisol concentrations were similar to those already characterised for plasma. Peak mean score for maternity blues (5.3 on Stein scale) was on day five postpartum (P < 0.02 compared with mean scores on other postpartum days). High postpartum scores for maternity blues were associated with high antenatal progesterone concentrations on day before delivery (P < 0.05), with high rate of rise of antenatal progesterone concentrations (P < 0.05), with decreasing progesterone concentrations from day of delivery to day of peak blues score (P > or = 0.01), and with low progesterone concentrations on day of peak blues score (P < 0.01). Seventy eight women were designated as having maternity blues (peak score > or = 8 on Stein scale) while 39 had no blues. Women with blues had significantly higher antenatal progesterone concentrations and lower postnatal concentrations than women without blues (geometric mean progesterone concentrations: one day before delivery 3860 pmol/l v 3210 pmol/l respectively, P = 0.03; ten days postpartum 88 pmol/l v 114 pmol/l, P = 0.048). Cortisol concentrations were not significantly associated with mood. CONCLUSION--Maternal mood in the days immediately after delivery is related to withdrawal of naturally occurring progesterone.     

Effects of Artificial Dawn and Morning Blue Light on Daytime Cognitive Performance,Well-being,Cortisol and Melatonin Levels

Light exposure elicits numerous effects on human physiology and behavior, such as better cognitive performance and mood. Here we investigated the role of morning light exposure as a countermeasure for impaired cognitive performance and mood under sleep restriction (SR). Seventeen participants took part of a 48h laboratory protocol, during which three different light settings (separated by 2?wks) were administered each morning after two 6-h sleep restriction nights: a blue monochromatic LED (light-emitting diode) light condition (BL; 100?lux at 470?nm for 20?min) starting 2?h after scheduled wake-up time, a dawn-simulating light (DsL) starting 30?min before and ending 20?min after scheduled wake-up time (polychromatic light gradually increasing from 0 to 250?lux), and a dim light (DL) condition for 2?h beginning upon scheduled wake time (<8?lux). Cognitive tasks were performed every 2?h during scheduled wakefulness, and questionnaires were administered hourly to assess subjective sleepiness, mood, and well-being. Salivary melatonin and cortisol were collected throughout scheduled wakefulness in regular intervals, and the effects on melatonin were measured after only one light pulse. Following the first SR, analysis of the time course of cognitive performance during scheduled wakefulness indicated a decrease following DL, whereas it remained stable following BL and significantly improved after DsL. Cognitive performance levels during the second day after SR were not significantly affected by the different light conditions. However, after both SR nights, mood and well-being were significantly enhanced after exposure to morning DsL compared with DL and BL. Melatonin onset occurred earlier after morning BL exposure, than after morning DsL and DL, whereas salivary cortisol levels were higher at wake-up time after DsL compared with BL and DL. Our data indicate that exposure to an artificial morning dawn simulation light improves subjective well-being, mood, and cognitive performance, as compared with DL and BL, with minimal impact on circadian phase. Thus, DsL may provide an effective strategy for enhancing cognitive performance, well-being, and mood under mild sleep restriction.