Influences of the normal menstrual cycle on physiologic functioning during behavioral stress

Social-evaluative threat: Stress response stages and influences of biological sex and neuroticism

Social-evaluative threat (SET) - when the self could be negatively judged by others - can cause pronounced responses in the different stress systems: threat/challenge appraisal, the sympathetic (SNS) and parasympathetic (PNS) nervous systems, experienced motivation and affect, and the hypothalamus-pituitary-adrenal (HPA) axis. Here, we utilize a four-stage stress response model to shed light on the complex associations between different stress responses, where earlier stages are hypothesized to predict later stages. Additionally, we take into account important moderators, such as biological sex (controlling for menstrual cycle phase), personality traits (neuroticism and extraversion), and baseline stress levels. Thirty-seven men and 30 women in their luteal phase participated in an impromptu public speaking task to induce SET. Stress responses in four different stages were measured using: self-reported appraisal (threat or challenge, stage 1: S1), cardiovascular measures (pre-ejection period as SNS index, respiratory sinus arrhythmia as PNS index, S2), self-reported motivation and affect (state approach motivation, state anxiety, S3) and endocrine measures (cortisol as HPA index, S4). Stress reactivity was calculated by subtracting individual peaks from baseline. Results showed that SET induced pronounced stress reactivity in stages two to four. Against expectations, self-reported appraisal (S1) or motivation and affect (S3) did not predict later stress reactivity. As hypothesized, increased SNS (but not PNS) reactivity (S2) predicted increased HPA reactivity (S4). Bayesian model comparison confirmed the absence of sex differences in stress reactivity, likely due to controlling for menstrual cycle phase and sex differences in neuroticism levels. Higher trait neuroticism predicted blunted SNS (S2) and HPA (S4) reactivity, while higher baseline stress levels predicted blunted stages two and three reactivity overall. In conclusion, this rigorously controlled experiment partly supports and partly contradicts previous findings regarding associations between stress response stages, and offers new insight into the causes of blunted HPA responses in women.

The influence of ovulation on postural stability (Biodex Balance System) in young female

The purpose of this study was to examine the influence of ovulation (OV) on dynamic balance in young female. Thirty-two eumenorrheic healthy women participated in Biodex Balance System (BBS) test for postural stability and a limit of stability menstrual cycle. BBS was tested in the menses (MS), OV, and luteal phase (LP). The limits of stabilities (total, forward-left, forward-right, backward-left, and backward-right) were significantly higher in the OV (total, 61.44±14.77; forward-left, 67.50± 15.17; forward-right, 69.50±14.43; backward-left, 64.00±20.32; and back-ward-right, 69.06±13.59) than in the MS (total, 55.44±14.63; forward-left, 60.00±15.98; forward-right, 62.17±9.78; backward-left, 57.83±19.09; and backward-right, 57.28±13.73). Furthermore, the LP (65.11±13.79) was a significantly higher limit of stability than MS (57.28±13.73) during back-ward-right. The present study showed that estrogen negatively influences postural stability. The postural sway in limits of stabilities (total, forward-left, forward-right, backward-left, and backward-right) were significantly the greatest in the OV. Since there is a different postural stability between MS, OV, and LP, this should be taken into account when devising training programs to avoid risk factor of fall and joint injury.

Effort analysis of gender differences in cardiovascular response: Further evidence involving a traditionally feminine incentive

Participants were presented a moderately- or impossibly difficult cumulative mental addition task with instructions that they could win a traditionally feminine- or masculine incentive if they achieved a 90% success rate. When the incentive was feminine, systolic blood pressure responses during the task period were stronger under moderately difficult conditions among women, but low irrespective of difficulty among men - creating a gender difference only when difficulty was moderate. By contrast, when the incentive was masculine, systolic-, mean arterial- and, to a lesser degree, diastolic blood pressure responses during the task period were stronger under moderately difficult conditions irrespective of gender. The former finding confirmed expectations and adds substantively to the body of evidence favoring a recent effort analysis of gender influence on CV response to performance challenge. The latter findings conflict with what was first expected, but can be understood in terms of post hoc reasoning extended in light of participants' ratings of the masculine incentive.

Role of the ovarian cycle on neural cardiovascular control in sleep-deprived women

The midluteal (ML) phase of the ovarian cycle is often sympathoexcitatory compared with the early follicular (EF) phase. We recently reported that 24-h total sleep deprivation (TSD) augmented cardiovascular reactivity in both men and women, but that sex differences existed in resting muscle sympathetic nerve activity (MSNA) responses to TSD. In the present study, we hypothesized increased resting MSNA and augmented cardiovascular reactivity to acute laboratory stressors during the ML phase in sleep-deprived women. Heart rate (HR), mean arterial pressure (MAP), forearm vascular conductance (FVC), and MSNA were measured in 14 eumenorrheic women (age, 20 ± 1 yr) during 10 min supine rest, 5 min mental stress (MS) trial, and 2 min cold pressor test (CPT) trial. Subjects were tested twice after TSD: once during EF phase and once during ML phase (randomized, crossover design). Estradiol (29 ± 2 vs. 63 ± 8 pg/ml, P = 0.001) and progesterone (1.6 ± 0.2 vs. 4.4 ± 0.7 ng/ml, P = 0.002) were elevated during the ML phase. Resting supine MAP (75 ± 2 vs. 72 ± 1 mmHg, P = 0.042) was lower during the ML phase. In contrast, resting supine HR, MSNA, and FVC were not significantly different between EF and ML phases. MAP, HR and FVC reactivity to MS were not statistically different between the EF and ML phases. Similarly, MAP and HR reactivity to CPT were not different between the ovarian phases. Contrary to our original hypothesis, the ML phase was not associated with sympathoexcitation or exaggerated cardiovascular reactivity in sleep-deprived premenopausal women. However, our data reveal elevated resting blood pressure during the EF phase in sleep-deprived women.

Study of cardiovascular reactivity to mental stress in different phases of menstrual cycle

BACKGROUND

It is a well known fact that normally female sex hormone levels fluctuate during the menstrual cycle. The presence of receptors for these hormones on both heart and blood vessels may also hint at variations in physiological functions during menstrual cycle. So this study was an attempt to determine whether the follicular and luteal phases of menstrual cycle are characterized by variations in cardiovascular parameters in the resting state and also examine changes in cardiovascular reactivity to mental stress challenge during both the phases of menstrual cycle.

METHODOLOGY

Thirty healthy females in the age group of 18-25 years with regular menstrual cycles fulfilling the inclusion criteria were examined for cardiovascular parameters (heart rate and blood pressures) at rest and their reactivity to mental stress during the follicular and luteal phase and were compared by using paired t-test. A p-value of <0.05 was considered as statistically significant.

RESULTS

The women included in the study produced the well known reactivity to mental stress, in terms of blood pressure and heart rate increases, but the two phases of menstrual cycle were indistinguishable in so far as reactivity patterns were considered. The resting values of these cardiovascular parameters were also alike during the two phases.

CONCLUSION

We were unable to unearth any differences in resting and reactivity values of cardiovascular parameters during the course of a normal menstrual cycle. This shows that stress reactivity variations during different phases of menstrual cycle may not be due to variations in hormonal levels per se, but due to collusion of hormonal variations and unknown genetic influences.

Mechanisms underlying hemodynamic and neuroendocrine stress reactivity at different phases of the menstrual cycle

This study examined the association of menstrual cycle phase with stress reactivity as well as the hormonal and neuroendocrine mechanisms contributing to cycle effects. Fifty-seven women underwent a modified Trier Social Stress Test during the early follicular, late follicular, and luteal phases of the menstrual cycle. Greater increases in cardiac index (CI) and greater decreases in vascular resistance index (VRI) during speech were observed in the luteal phase relative to other phases, while greater increases in epinephrine (EPI) was observed during the late follicular and luteal phases compared to the early follicular phase. Luteal phase estradiol predicted luteal EPI reactivity but not CI or VRI reactivity, while luteal phase EPI reactivity predicted luteal phase CI and VRI reactivity. Thus, cycle-related changes in EPI reactivity may be a stronger determinant of cycle effects on hemodynamic reactivity than sex hormones per se.

Menstrual mood disorders are associated with blunted sympathetic reactivity to stress

OBJECTIVE

Few studies have directly compared women with a menstrually related mood disorder (MRMD) with women who have suffered from depression for stress reactivity phenotypes. It is unclear whether blunted responses to stress in women with a MRMD reflect a unique phenotype of MRMDs or may be explained by a history of depression.

METHODS

We assessed cardiovascular reactivity to stress in four groups: 1) Women with a MRMD without a history of depression (n=37); 2) women with a MRMD plus a history of depression (n=26); 3) women without a MRMD and without a history of depression (n=43); and 4) women without a MRMD but with a history of depression (n=20).

RESULTS

Women with a MRMD showed blunted myocardial (heart rate and cardiac index) reactivity to mental stress compared to non-MRMD women, irrespective of histories of depression. Hypo-reactivity to stress predicted greater premenstrual symptom severity in the entire sample. Women with a MRMD showed blunted norepinephrine and diastolic blood pressure stress reactivity relative to women with no MRMD, but only when no history of depression was present. Both MRMD women and women with depression histories reported greater negative subjective responses to stress relative to their non-MRMD and never depressed counterparts.

CONCLUSION

Our findings support the assertion that a blunted stress reactivity profile represents a unique phenotype of MRMDs and also underscore the importance of psychiatric histories to stress reactivity. Furthermore, our results emphasize the clinical relevance of myocardial hypo-reactivity to stress, since it predicts heightened premenstrual symptom severity.

Stress-induced inflammatory responses in women: effects of race and pregnancy

OBJECTIVE

African Americans experience preterm birth at nearly twice the rate of whites. Chronic stress associated with minority status is implicated in this disparity. Inflammation is a key biological pathway by which stress may affect birth outcomes. This study examined the effects of race and pregnancy on stress-induced inflammatory responses.

METHODS

Thirty-nine women in the second trimester of pregnancy (19 African American, 20 white) and 39 demographically similar nonpregnant women completed an acute stressor (Trier Social Stress Test). Psychosocial characteristics, health behaviors, and affective responses were assessed. Serum interleukin (IL)-6 was measured at baseline, 45 minutes, and 120 minutes poststressor.

RESULTS

IL-6 responses at 120 minutes poststressor were 46% higher in African Americans versus whites (95% confidence interval = 8%-81%, t(72) = 3.51, p = .001). This effect was present in pregnancy and nonpregnancy. IL-6 responses at 120 minutes poststressor tended to be lower (15%) in pregnant versus nonpregnant women (95% confidence interval = -5%-32%, p = .14). Racial differences in inflammatory responses were not accounted for by demographics, psychological characteristics, health behaviors, or differences in salivary cortisol. Pregnant whites showed lower negative affective responses than did nonpregnant women of either race (p values ≤ .007).

CONCLUSIONS

This study provides novel evidence that stress-induced inflammatory responses are more robust among African American women versus whites during pregnancy and nonpregnancy. The ultimate impact of stress on health is a function of stressor exposure and physiological responses. Individual differences in stress-induced inflammatory responses represent a clear target for continued research efforts in racial disparities in health during pregnancy and nonpregnancy.

Salivary cortisol, heart rate, electrodermal activity and subjective stress responses to the Mannheim Multicomponent Stress Test (MMST)

The availability of effective laboratory paradigms for inducing psychological stress is an important requirement for experimental stress research. Reliable protocols are scarce, usually laborious and manpower-intensive. In order to develop an economical, easily applicable standardized stress protocol, we have recently tailored the Mannheim Multicomponent Stress Test (MMST). This test has been shown to induce relatively high stress responses without focusing on social-evaluative components. In this study we evaluated changes in electrodermal activity and salivary cortisol in response to the MMST. The MMST simultaneously combines cognitive (mental arithmetic), emotional (affective pictures), acoustic (white noise) and motivational stressors (loss of money). This study comprised two independent experiments. For experiment 1, 80 female subjects were recruited; 30 subjects (15 females) participated in experiment 2. Significant changes in electrodermal activity and salivary cortisol levels in response to MMST exposure were found. Subjective stress and heart rate responses were significantly increased in both experiments. These results indicate that the MMST is an economical stress paradigm which is also applicable in larger cohorts or multicenter studies for investigating stress reactions. As social-evaluative threat is not the main stress component of the MMST, this procedure represents a useful and complementary alternative to other established stress protocols.

Histories of major depression and premenstrual dysphoric disorder: Evidence for phenotypic differences

This study examined unique versus shared stress and pain-related phenotypes associated with premenstrual dysphoric disorder (PMDD) and prior major depressive disorder (MDD). Sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA)-axis measures were assessed at rest and during mental stress, as well as sensitivity to cold pressor and tourniquet ischemic pain tasks in four groups of women: (1) non-PMDD with no prior MDD (N=18); (2) non-PMDD with prior MDD (N=9); (3) PMDD with no prior MDD (N=17); (4) PMDD with prior MDD (N=10). PMDD women showed blunted SNS responses to stress compared to non-PMDD women, irrespective of prior MDD; while women with prior MDD showed exaggerated diastolic blood pressure responses to stress versus never depressed women, irrespective of PMDD. However, only in women with histories of MDD did PMDD women have lower cortisol concentrations than non-PMDD women, and only in non-PMDD women was MDD associated with reduced cold pressor pain sensitivity. These results suggest both unique phenotypic differences between women with PMDD and those with a history of MDD, but also indicate that histories of MDD may have special relevance for PMDD.

Cardiovascular, hormonal, and emotional responses to the TSST in relation to sex and menstrual cycle phase

The prevalence of stress disorders differs between men and women. An understanding of how men and women vary in acute stress responses may help to understand these sex differences. We compared responses to the TSST and a control task in healthy men (N=28) and women tested in two phases (Follicular N=29, Luteal N=23) of the menstrual cycle. Men exhibited greater cortisol responses to stress than women in either phase. Luteal women exhibited the greatest subjective and allopregnanolone responses to stress, whereas follicular women exhibited blunted noradrenaline responses. Partial correlations controlling for group differences revealed that individuals who were most sensitive to the subjective effects of stress exhibited the largest salivary cortisol, noradrenaline, and allopregnanolone responses and the smallest progesterone responses to stress. We discuss our findings in the context of sex differences in the prevalence of stress-linked disorders.

Gender and stress: differential psychophysiological reactivity to stress reexposure in the laboratory

Research has shown that women are more prone to the development of depression and anxiety disorders throughout their lifetimes. Stress reactivity and adaptation to repeated stressors have been linked to depression and anxiety, but studies examining gender differences in psychophysiological responses to repeated stressors are very limited. This study examined gender differences in response to initial and repeated exposure to a laboratory stressor as well as potential mechanisms for these differences. Participants viewed a Holocaust video on two occasions with a 2-day interval between sessions. Self reported negative affect and cardiovascular reactivity were recorded at both sessions. Although gender differences were not found following initial exposure, women exhibited significantly greater heart rate (HR) and negative affect (NA) reactivity to the second exposure as compared to men. Women also reported significantly greater intrusive thoughts and avoidance after the first exposure than men, but these were not found to be significant mediators. The findings indicate that women may be more vulnerable to repeated stress exposures compared to men suggesting sensitization. The implications of our findings and suggestions for future research are discussed.

Neuroendocrine stress responses to an oral academic examination: No strong influence of sex, repeated participation and personality traits

Public speaking tasks have been widely used as laboratory stressors in human research. Fewer studies have investigated similar real life situations like oral examinations and results have been inconsistent. The present study investigated salivary cortisol (as a marker of hypothalamus-pituitary-adrenal (HPA) activity) and salivary alpha-amylase (sAA as a marker of sympathetic nervous system (SNS) activity) within the context of a university examination. Subjects were 40 undergraduate students who participated in an oral examination. Of these, 20 also participated in a second examination within a few weeks. Cortisol and sAA were measured immediately before and after the examination and on a control day. Additionally, subjects filled out personality questionnaires. A strong anticipatory increase in salivary cortisol and sAA as well as more modest further increases between the pre- and post-measurements were detected during the examination. Sex or oral contraceptive use had no influence on either measure. In addition, no significant differences between the first and second examination were observed. The findings indicate the neuroendocrine stress responses to laboratory stressors and to heralded real life stressors as well as the modulatory variables involved differ from each other.

Acute psychosocial challenge and cardiac autonomic response in women: the role of estrogens, corticosteroids, and behavioral coping styles

Theoretical statements, as well as clinical and experimental data, suggest that the amplitude of cardiovascular reactivity to acute stressors can be a good predictor of preclinical and clinical cardiovascular states. The aim of the present study is to investigate the role of estrogens, the hypothalamic-pituitary-adrenocortical activity, and the behavioral profile in individual cardiac autonomic reactivity to brief laboratory stressors in women. Thirty-six adult, healthy women were exposed to a stress interview and a mental task test, each lasting 5 min. They were assigned to two experimental groups: D4, i.e. 4 days after menses beginning (follicular phase, n=18), and D14, i.e. 14 days after menses beginning (ovulatory phase, n=18). The cardiac measurements in the baseline, stress and recovery periods consisted in heart rate (average R-R interval) and parasympathetic tone (r-MSSD) quantification, while the HPA axis activity and stress reactivity were assessed via plasma cortisol and dehydroepiandrosterone concentrations. The ethological profile during the interview was drawn by means of non-verbal behavior analysis. The cardiac, adrenocortical and behavioral responses to the two stressors were similar in groups D4 and D14, despite significantly higher estradiol levels in the latter. Subjects with higher pre-stress cortisol levels had higher heart rate and lower vagal activity in the baseline, stress and recovery phases. Women showing higher level of submission were characterized by higher heart rate acceleration and vagal withdrawal during both the interview and the recovery phase. In addition, the subjects that exhibited greater displacement during the interview were also characterized by lower heart rate increments and less pronounced vagal suppression during post-stress recovery. In conclusion, the present results do not support a clear buffering role of estrogens in cardiovascular response to acute stressors. However, they confirm that baseline HPA axis activity can be predictive of cardiac autonomic activity and stress responsiveness. They also highlight the modulating role of the individual style of behavioral coping in cardiac sympathovagal stress reactivity. Therefore, the objective assessment of the individual behavioral profile via the analysis of non-verbal communication patterns might represent a powerful tool for identifying subjects with higher risk of cardiac events.

Sex, outcome expectancy, and cardiovascular response to a masculine challenge

Male and female participants were led to believe they could secure a low or high chance of winning a prize by meeting a modest standard on a purportedly masculine task, that is, a task on which men ostensibly had higher ability. As expected, systolic blood pressure responses measured during performance were greater for women than men when the chance of winning was high, but low for both groups when the chance of winning was low. Similar effects were observed for diastolic and mean arterial pressure responses, although analysis of the mean arterial pressure data produced only a main effect for the chance factor. These results conceptually replicate cardiovascular findings obtained in a previous sex difference study. They also confirm the implication of previous ability perception studies that effort-related cardiovascular responses should be low for both sexes when the importance of meeting a gender-relevant challenge is low.

The effects of sex and hormonal status on the physiological response to acute psychosocial stress

Whether one is male or female is one of the most important determinants of human health. While males are more susceptible to cardiovascular and infectious disease, they are outnumbered by women for many autoimmune disorders, fibromyalgia and chronic pain. Recently, individual differences in the physiological response to stress have emerged as a potentially important risk factor for these disorders. This raises the possibility that sex differences in prevalence of disease could at least in part be explained by sex differences in the nature of the physiological response to stress. In a psychophysiological laboratory, the autonomic nervous system response can be provoked by many different stressors including physical, mental and psychosocial tasks, while the hypothalamic-pituitary-adrenal axis (HPAA) response seems to be more specific to a psychosocial challenge incorporating ego involvement. The responses of both systems to different psychosocial challenges have been subject to extensive research, although in respect of sex differences the HPAA response has probably been more systematically studied. In this review, we focus on sex differences in HPAA and autonomic nervous system responses to acute psychosocial stress. Although some differences are dependent on the stressor used, the responses of both systems show marked and consistent differences according to sex, with the phase of the menstrual cycle, menopausal status and pregnancy having marked effects. Between puberty and menopause, adult women usually show lower HPAA and autonomic responses than men of same age. However, the HPAA response is higher in the luteal phase, when for example post stress free cortisol levels approach those of men. After menopause, there is an increase in sympathoadrenal responsiveness, which is attenuated during oral hormone replacement therapy, with most evidence suggesting that HPAA activity shows the same trends. Interestingly, pregnancy is associated with an attenuated response of the sympathoadrenal and HPAA systems at least as assessed by biochemical stimulation. It is likely that these sex differences in autonomic function are a result of estrogen exposure which attenuates sympathoadrenal responsiveness. The HPAA is however somewhat more complex and evidence now suggests the influence of other modifiers such as arginine vasopressin (AVP) and the regulation of circulating cortisol bioavailability by corticosteroid-binding globulin (CBG). The pronounced and multi-faceted sex differences in stress responsiveness suggest that they are a product of a strong evolutionary pressure. We hypothesise that this has to a great deal been driven by the need to protect the fetus from the adverse effects of maternal stress responses, in particular excess glucocorticoid exposure. Studying this hypothesis may have a fundamental impact on our understanding about how adult health is set during early life and how adult disease could be prevented in men and women.

Do blood pressure and heart rate responses to perceived stress vary according to endogenous estrogen level in women?

The results of experimental studies suggest that estrogen may blunt blood pressure responses to stress, but increase heart rate responses. We investigated whether within-person associations of perceived stress with blood pressure and heart rate during normal working life in 26 premenopausal and 7 postmenopausal women varied according to endogenous estrogen level. Each woman measured her own blood pressure and heart rate and completed a diary reporting perceived stress levels on six occasions on each of 2 working days. Premenopausal women were assessed once between days 4 and 6 of their menstrual cycle (low estrogen) and again between days 11 and 13 (high estrogen), and urine samples were taken to verify expected variation in estrogen level. Results showed that perceived stress was significantly positively associated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate in the group as a whole. This association did not differ according to menopausal status. There was no difference in the association of perceived stress with SBP or DBP in premenopausal women according to day of assessment, but heart rate reactivity to perceived stress was significantly higher on the high-estrogen day. Our findings thus provide evidence that heart rate responses to perceived stress during everyday working life vary according to estrogen level in premenopausal women, but no evidence that blood pressure responses to stress vary according to endogenous estrogen level in women.

Social support versus social evaluation: unique effects on vascular and myocardial response patterns

OBJECTIVES

This study examined the effects of companion presence and evaluation on cardiovascular reactivity to an acute stressor.

METHODS

Eighty-two women completed a speech task in one of four conditions: with an evaluative companion present, with a nonevaluative companion present, alone while being evaluated by a companion with a video camera, or alone while the companion waited outside.

RESULTS

A significant interaction between companion condition and evaluative condition on systolic blood pressure was found; women who were evaluated while alone demonstrated significantly greater reactivity than did women who were in the nonevaluative alone condition. Furthermore, both potential for evaluation and the presence of a companion had important influences on hemodynamic parameters underlying the blood pressure response. Specifically, those in evaluative conditions showed greater myocardial responding than those in nonevaluative conditions and those in alone conditions showed greater vascular responding than did those with companions present. Taken together, those in the evaluative alone condition demonstrated systolic blood pressure responses reflecting both myocardial and vascular contributions.

CONCLUSIONS

Social support and social evaluation have unique effects on vascular and myocardial responding. The implications for future research include focus on the stress-buffering model of social support and the value of including impedance cardiography measures in investigations of cardiovascular functioning.

Sympathetic skin response in premenstrual syndrome

Premenstrual syndrome is a term which includes a broad group of emotional, behavioral and physical symptoms that occur for several days before menses and subside following the menstrual period. Many women experience premenstrual syndrome symptoms, particularly physical ones such as breast tenderness and swelling. Approximately 5-10% women suffer from severe premenstrual syndrome and another 30-40% have moderate symptoms. Premenstrual syndrome continues to be an unsolved problem. In this study, we evaluated 24 premenstrual syndrome patients and 20 healthy women in the control group. The ages of the women were 22-34 years (mean +/- SD: 25+/-3) for the premenstrual syndrome group and 23-34 (25+/-3) for the control group. The sympathetic skin response was recorded from the palms, soles and genital regions by using electrical stimuli to the median nerve at the wrist. The sympathetic skin response was recorded twice, in the follicular and late luteal phases of menstruation. The follicular and late luteal phase sympathetic skin response of the two groups were compared. The amplitudes and latency values of the late luteal and follicular phase sympathetic skin response from the premenstrual syndrome group and control group women were statistically similar. We also did not find any latency or amplitude difference in the sympathetic skin response obtained from the three regions of the premenstrual syndrome patients and the control group. We checked sympathetic skin response in the symptomatic (late luteal phase) and asymptomatic (follicular phase) periods of patients with premenstrual syndrome, a disorder known to have many autonomic symptoms, to determine whether there was sudomotor sympathetic involvement. The results of our PMS patients indicate at the very least that there is no difference with the control subjects as regards peripheral sudomotor functions.

Sex differences in stress responses: social rejection versus achievement stress

BACKGROUND

Sex differences in stress responses may be one mechanism underlying gender differences in depression. We hypothesized that men and women would show different adrenocortical responses to different stressors. In particular, we predicted that women would show greater responses to social rejection stressors, whereas men would demonstrate greater responses to achievement stressors.

METHODS

Following a rest session in which they habituated to the laboratory, 50 healthy volunteers (24 men and 26 women, mean age 19.1, SD = 1.13) were randomly assigned to achievement or rejection stress conditions. The achievement condition involved a mathematical and a verbal challenge; the rejection condition involved two social interaction challenges. Self-reported affect and salivary cortisol were measured throughout each stress session (baseline, stress, and poststress periods).

RESULTS

There were no sex differences in mood ratings following the stressors; however, cortisol responses showed the predicted gender by condition by time interaction. Men showed significantly greater cortisol responses to the achievement challenges, but women showed greater cortisol responses to the social rejection challenges.

CONCLUSIONS

Women appear more physiologically reactive to social rejection challenges, but men react more to achievement challenges. Women's greater reactivity to rejection stress may contribute to the increased rates of affective disorders in women.

Oral contraceptive use is associated with increased cardiovascular reactivity in nonsmokers

Women who smoke and take oral contraceptives (OCs) have significantly increased risk of cardiovascular disease, but the exact mechanismsfor the increased risk are not known. Cardiovascular reactivity to psychological stress may be one mechanism for the enhanced risk, but the small number of studies examining whether OC users who smoke have greater reactivity have produced mixed results. The purpose of this study was to examine the effect of chronic cigarette smoking, acute nicotine administration, and OC use on cardiovascular and lipid reactivity. Sixty healthy women, half of whom had been using OCs for at least the previous 6 months, participated in the study. Approximately two thirds were smokers and were randomized to be tested after either a 12-hr nicotine deprivation or administration of nicotine gum. One third were nonsmokers. Heart rate, blood pressure, and lipid measures were taken at rest, during a videotaped speech task, and during recovery from the task. Results indicated that, among OC nonusers, there was no effect of smoking status or nicotine administration on cardiovascular reactivity. However, among OC users, nonsmokers had significantly greater heart rate and diastolic blood pressure reactivity to stress. These data show that acute nicotine administration, in the form of nicotine gum, has no effect on cardiovascular or lipid stress reactivity in women. However OC use among nonsmoking women is associated with greater cardiovascular reactivity to stress.

Psychophysiological correlates of individual differences in patterns of hemodynamic reactivity

The present study delineates a method for the quantification of six hemodynamic reactivity patterns, in response to a laboratory stressor, and examines the psychophysiological correlates of individual differences in these patterns. One hundred and ninety-four young adult men and women participated in rest periods and two laboratory stressors, mental arithmetic and an anger recall interview. Measures were taken of blood pressure, heart rate, and cardiac output, from which total peripheral resistance was derived, as well as state reports of feelings during the tasks. Six hemodynamic reactor patterns were identified: Non-reactors, Mild Myocardials, Mild Vasculars, Myocardials, Vasculars, and Dual Reactors, each associated with a unique profile of cardiac output and total peripheral resistance change. Myocardial reactors to the interview had the highest resting levels of blood pressure and total peripheral resistance. Dual reactors had the largest increases in diastolic reactivity; Dual and Myocardial reactors had the largest increases in systolic reactivity. The extreme reactor groups (Dual, Myocardial, Vascular) all reported greater task invigoration than the Non-reactors, who reported greater efforts to relax. Reactor groups were similar on anger-related trait affect. Based on both resting blood pressure and magnitude of task-induced reactivity, Myocardial and Dual reactors may be at the greatest risk for subsequent hypertension.

Cortisol circadian rhythms during the menstrual cycle and with sleep deprivation in premenstrual dysphoric disorder and normal control subjects

BACKGROUND

In this study we extended previous work by examining whether disturbances in the circadian rhythms of cortisol during the menstrual cycle distinguish patients with premenstrual dysphoric disorder (PMDD) from normal control (NC) subjects. In addition, we tested the differential response to the effects of early and late partial sleep deprivation on cortisol rhythms.

METHODS

In 15 PMDD and 15 NC subjects we measured cortisol levels every 30 min from 6:00 PM to 9:00 AM during midfollicular (MF) and late luteal (LL) menstrual cycle phases and also during a randomized crossover trial of early (sleep 3:00 AM-7:00 AM) versus late (sleep 9:00 PM-1:00 AM) partial sleep deprivation administered in two subsequent and separate luteal phases.

RESULTS

In follicular versus luteal menstrual cycle phases we observed altered timing but not quantitative measures of cortisol secretion in PMDD subjects, compared with NC subjects: in the LL versus MF phase the cortisol acrophase was a mean of 1 hour earlier in NC subjects, but not in PMDD subjects. The effect of sleep deprivation on cortisol timing measures also differed for PMDD versus NC subjects: during late partial sleep deprivation (when subjects' sleep was earlier), the cortisol acrophase was almost 2 hours earlier in PMDD subjects.

CONCLUSIONS

Timing rather than quantitative measures of cortisol secretion differentiated PMDD subjects from NC subjects both during the menstrual cycle and in response to early versus late sleep deprivation interventions.

Cardiovascular responses to open-field stress in rats: sex differences and effects of gonadal hormones

We studied sex differences in cardiovascular responses to stress using a new radio-telemetry model in which freely-moving Spontaneously Hypertensive rats (SHR) are exposed to open-field novelty stress. This model allowed simultaneous assessment of cardiovascular and behavioural responses to psychological stress. Female SHR in the diestrous stage of their estrous cycle had markedly greater pressor and tachycardic responses to open-field exposure when compared to either female rats not in diestrous or male SHR. Treatment of ovariectomized SHR with estrogen alone had no significant effect on cardiovascular reactivity, while a combined treatment of estrogen and progesterone slightly, but significantly attenuated their pressor response to open-field stress. In addition, treatment of castrated male rats with testosterone significantly enhanced their pressor responses to stress when compared to values obtained before treatment. None of the hormone treatments had any significant effect on heart rate responses to stress. Neither at different stages of the estrous cycle nor after hormone treatments were there any marked changes in behavioural responses in the open-field, making it unlikely that the differences in cardiovascular stress responses were caused by changes in behavioural activity. These data demonstrate differences in cardiovascular stress responses that seem to be dependent on the stage of the estrous cycle. They suggest that particularly androgens, such as testosterone, may enhance pressor responses to stress. On the other hand, a combination of estrogen and progesterone, rather than estrogen alone, may have a small attenuating effect on cardiovascular reactivity.

Hemodynamic and sympathetic nervous system responses to stress during the menstrual cycle

In this study, the impact of menstrual cycle phase on hemodynamic and sympathetic nervous system responses was examined during exposure to a battery of laboratory stressors. Participants were 40 healthy premenopausal women, aged 26 to 51. Impedance cardiography was used to measure stroke volume, heart rate, and cardiac output. Systemic vascular resistance was derived on the basis of concurrently recorded blood pressure and cardiac output. The menstrual cycle's effect on the sympathetic nervous system response was explored by evaluating plasma catecholamine responses during stress. In luteal compared with follicular subjects, systemic vascular resistance was significantly lower during all stress tasks (P < 0.03). Catecholamine responses were also significantly lower in luteal subjects (P < 0.004). The results suggest that the sympathetic nervous system may respond to stress differently during different phases of the menstrual cycle. This finding has implications for understanding "whitecoat hypertension" in women, and highlights the need to measure blood pressure during several office visits. Perhaps high blood pressure readings recorded during the follicular phase should be reexamined during the luteal phase before considering pharmacologic intervention.

Menstrual cycle, race and task effects on blood pressure recovery from acute stress

This study examined cardiovascular recovery from two standardized laboratory stressors in 68 healthy black and white normotensive women and men (mean age 33 years). Women were studied in a randomized order at the same time of day on two separate occasions, once during the follicular phase (days 7 to 10 following menses) and once during the luteal phase (days 7 to 10 following the leutenizing-hormone surge) of the menstrual cycle. Men were studied twice approximately 6 weeks apart. There were differential effects of the tasks on blood pressure recovery (change scores) with a mirror star task yielding poorer diastolic blood pressure recovery (p = 0.004) and an interpersonal speaking task yielding poorer systolic blood pressure recovery (p = 0.003). Across both tasks, blacks evidenced greater diastolic blood pressure recovery as compared to whites (p = 0.02). Black women showed greater diastolic blood pressure recovery in the luteal as compared to the follicular phase (p = 0.01), whereas white women evidenced no such change across the menstrual cycle. Correlation analysis across testing sessions generally revealed comparable temporal stability values for recovery as compared to reactivity measures. The findings support prior studies indicating racial differences in recovery from acute stress and extend these findings by suggesting that the menstrual cycle may differentially affect recovery in black versus white women.

Blood pressure, plasma NPY and catecholamines during physical exercise in relation to menstrual cycle, ovariectomy, and estrogen replacement

Some evidences indicate that the female sex hormones protect against the development of cardiovascular diseases. Modulation of sympathetic activity may be one of the possibilities. We investigated the influence of treadmill stress on blood pressure (BP) and plasma neuropeptide Y (NPY), norepinephrine (NE) and epinephrine (E) concentrations in 11 normotensive, menstruating women in the follicular (HWf) and luteal (HWl) phases and in eight ovariectomized women, before (OVX) and after estrogen supplementation (OVXe). Both at rest and during exercise there were no differences in BP between HWf and HWl and between OVX and OVXe. During stress BP was significantly lower in HWf and HWl than in OVX but not in OVXe. NPY did not differ significantly between the groups of women either at rest or during activity. We did not observe differences in resting and stimulated NE and E between HWf and HWl and between OVX and OVXe. Neither resting nor activated NE and E differed between the groups, except higher stimulated NE in OVX than in HWf. These results suggest that the female sex hormones may modulate the BP response to dynamic exercise. Our data support evidence that this influence may be exerted by circulating catecholamines and not by NPY.

Coping and appraisal of daily stressors predict heart rate and blood pressure levels in young women

An anger-provocation paradigm was used to assess the effects of coping processes and appraisal of daily stressors on stress reactivity in 33 normotensive undergraduate women. Participants performed a mental arithmetic and an interpersonal conflict task during the pre- and postmenstrual phases of their menstrual cycles. Increased use of the emotion-focused coping processes of tension reduction and positive reappraisal was correlated with lower levels of baseline heart rate, whereas distancing was associated with higher levels of systolic blood pressure reactivity during the conflict task. Perceiving daily stressors as more stressful was associated with higher baseline diastolic blood pressure levels. The authors concluded that the transactional model of stress is useful for generating hypotheses about factors that predict heart rate and blood pressure levels in women.

Cardiovascular stress response and coronary artery disease: evidence of an adverse postmenopausal effect in women

OBJECTIVES

To test the hypothesis that postmenopausal women demonstrate greater vascular instability, measured by enhanced cardiovascular stress responses during mental stress, compared with men and premenopausal women.

BACKGROUND

Recent data suggest that estrogen plays a role in regulating vascular tone. The possible consequences of estrogen deficiency during menopause on systemic vascular reactivity is largely unexplored.

METHODS

One hundred subjects (84 men and 16 women) underwent mental stress testing with radionuclide ventriculo graphy. Study subjects included 19 normal volunteers, 23 control subjects with chest pain syndromes or hypertension but without coronary artery disease, and 58 coronary artery disease subjects. The subjects performed a series of three mental stress tasks, during which hemodynamic data and radionuclide ventriculograms were obtained.

RESULTS

Overall, women demonstrated greater hemodynamic responses during mental stress measured by changes in heart rate, systolic and diastolic blood pressure, and double product compared with those of men (all p < 0.05). Women with coronary artery disease demonstrated greater heart rate, diastolic blood pressure, and double product stress responses than their male counterparts (all p < 0.05). Women of postmenopausal age demonstrated significantly greater systolic blood pressure reactivity than men or premenopausal women (p < 0.05).

CONCLUSIONS

Women of postmenopausal age have greater cardiovascular responses to stress than men or premenopausal women. These findings suggest an additional mechanism by which estrogen deficiency conveys a poor prognosis in female patients with coronary artery disease.

Effects of short-term suppression of ovarian hormones on cardiovascular and neuroendocrine reactivity to stress in women

The present study reduced the levels of ovarian hormones to early postmenopausal levels by a GnRH agonist and evaluated the effects of a temporary suppression of ovarian hormones on premenopausal women's cardiovascular and neuroendocrine responses to laboratory challenges. The stress responses of 24 healthy young women were evaluated during three tasks during the early follicular phase and then after three monthly injections of Lupron, which suppressed their levels of estradiol, FSH, and LH. Thereafter, half the group resumed menstrual cycles (labeled Cycle), and half continued having Lupron injections in combination with transdermal estradiol (labeled Patch) and all were reevaluated a third time. A third group (labeled Control) of 12 women had four monthly injections of Lupron first and then were evaluated the first time. After their cycles resumed, they were reevaluated twice 3 months apart. Results showed that the magnitude of the blood pressure and catecholamine changes declined over the three evaluations, suggesting that the women's stress responses habituated. Although the suppression of ovarian hormone levels led to alterations in ovarian hormones for several months, which were accompanied by typical menopausal symptoms, cardiovascular and neuroendocrine responses to stress did not vary. This study did not test the effects of current estrogen exposure or of long term suppression of ovarian hormones upon cardiovascular and neuroendocrine responses.

Coping and parental history of cardiovascular disorders influence blood pressure in women tested during different phases of their menstrual cycles

An anger-provocation paradigm was used to assess coping and stress reactivity in 20 women with a positive parental history of cardiovascular disorders and 14 women whose parents had no cardiovascular disease. Frequency of seeking social support in the natural environment was assessed, as were systolic and diastolic blood pressures, while the women performed anger-inducing arithmetic and speech-stressor tasks during the premenstrual and postmenstrual phases. Premenstrually, the women with a positive cardiac history sought support less frequently than those with a negative history. No differences were found between the groups postmenstrually. When the women were identified according to the frequency with which they sought social support, those who more often sought support registered lower baseline blood pressure levels than those women who less often sought support during both cycle phases. Extending the stress-buffering effects of social support to include efforts at seeking support is discussed.

Cardiovascular, endocrine, and receptor measures as related to sex and menstrual cycle phase

OBJECTIVE

The present study was undertaken to elucidate possible mechanisms underlying sex differences in cardiovascular measures or reactivity to challenge. Because there is vastly diverging literature on the issue, we tried to control for endocrine and psychological factors, which might contribute to some of the apparent discrepancies.

METHODS

Blood pressure, heart rate, adrenaline, and noradrenaline in women (N = 24) and men (N = 14) were examined during baseline and challenge (Stroop Test and Cold Face Test). Adrenoceptor density on lymphocytes (beta 2) and platelets (alpha 2) were determined to examine possible sex differences in underlying cardiovascular mechanisms. Gender effects were controlled by assessing gender role orientation and task appraisal. Women were tested during either the follicular (N = 12) or the luteal (N = 12) phase of the menstrual cycle (verified by estradiol, progesterone, and luteinizing hormone).

RESULTS

Follicular and luteal phase women did not differ in any parameter except progesterone. We observed sex-related differences in absolute levels of physiological parameters, the male group having higher systolic blood pressure levels, higher adrenaline plasma concentrations, and significantly more alpha 2-adrenergic receptors. Both challenges elicited pronounced cardiovascular and endocrine responses. Men and women did not differ in response magnitude, in task appraisal, or gender role orientation.

CONCLUSIONS

The assumption that female sex hormones reduce reactivity to challenge is not supported by our data. The frequently reported male/female differences in reactivity may be caused by an interaction of gender and task characteristics.

Reflex control of autonomic function induced by posture change during the menstrual cycle

This study was designed to determine whether autonomic regulation induced by posture changes varies during the menstrual cycle. Heart rate variability (HRV) was analyzed in women with normal menstrual cycles (n = 10, age range 20-37 years) during 3 min periods of controlled frequency breathing (15 breaths/min) in supine followed by sitting positions. In a supine or sitting position, high frequency (HF) components of HRV, which reflects only parasympathetic activity, were significantly high in the follicular phase compared with those in the menstrual phase, suggesting that parasympathetic nerve activity increases in this phase. Following the change of position to sitting from supine, the HF component decreased significantly in the menstrual, ovulatory and luteal phases, but not the follicular or premenstrual phase. After changing the position to sitting, the low to high frequency component ratio, which reflects the balance of autonomic nerve activities, was increased significantly in the menstrual, luteal and premenstrual phases, indicating that sympathetic nerve activities in these phases became predominant by the sitting position. These results suggest that parasympathetic nerve activity is predominant in the follicular phase, resulting in an impairment of baroreflex caused by posture changes. Moreover, baroreflex control of the sympathetic component, not the parasympathetic component, increases in the premenstrual phase, while the reflex response of the sympathetic component is less in the ovulatory phase compared with the menstrual or luteal phase. We concluded that baroreflex regulation of autonomic functions induced by changing positions is modified during the menstrual cycle. A difference of a balance of ovarian hormones may be responsible for these changes of autonomic functions during the menstrual cycle.

Differential hostility profiles accompany different hemodynamic response patterns

Cardiovascular reactivity has been proposed as a mechanism by which psychosocial variables may lead lo coronary heart disease. Although reactivity as a generalized response has been linked lo psychological factors, there are specific hemodynamic profiles that underlie blood pressure reactivity. This study characterized subsets of young adults as myocardial or vascular reactors, in response to three laboratory tasks: mental arithmetic, videogame, and anger recall interview. Vascular reactors had higher diastolic blood pressure increases to all tasks, whereas reactor groups were equivalent at rest and on systolic blood pressure responses. Correlational analyses were conducted to determine whether psychological dimensions are uniquely associated with myocardial or vascular reactors' cardiovascular responses, at rest and during acute stressors. For myocardial reactors, resting systolic blood pressure was higher in hostile and suspicious individuals, whereas reactivity was linked to impulsivity. For vascular reactors, low trust, low gregariousness, and high depression were associated with diastolic reactivity to tasks. The predictive validity of hostility, distrust, sociability, and depression for cardiovascular pathology may vary with reactor type.

Menstrual cycle effects on catecholamine and cardiovascular responses to acute stress in black but not white normotensive women

This study examined cardiovascular and catecholamine responses to two standardized laboratory stressors in 33 healthy age- and weight-matched black and white normotensive women (mean age, 32 years) during two phases of the menstrual cycle. Subjects were studied in a randomized order at the same time of day on two separate occasions approximately six weeks apart, once during the follicular phase (days 7 to 10 after menses) and once during the luteal phase (days 7 to 10 after the leutenizing hormone surge) of the menstrual cycle. Black women has higher systolic (P=.01) and diastolic (P=.01) pressures compared with white women. Black women showed greater diastolic pressure (P <.01) and plasma epinephrine (P <.05) responses to stress during the follicular compared with the luteal phase of the menstrual cycle; white women showed no significant changes in these variables. The findings extend the literature on race differences in responsivity to stress and indicate that in contrast to white women, reproductive hormones do influence cardiovascular and catecholamine responsivity to stress in black women.

Stress responsivity in exercisers and non-exercisers during different phases of the menstrual cycle

It has been suggested that, premenstrually, women are more vulnerable to the effects of stress. It has also been proposed that the fitter the individual is, the less the body responds to, and the more quickly it recovers from, a stressful experience. The present study investigated whether premenstrual sensitivity to a stressful laboratory task would be attenuated in women who exercised. Responses to the task across the menstrual cycle were studied in 20 women who exercised regularly and 20 women who were sedentary. Heart rate and blood pressure as well as subjective mood responses were measured in each of three phases: premenstrual, menstrual and postmenstrual. Exercising and sedentary women differed in sensitivity to stress: heart rate responsivity to stress was less in exercisers, but mood fluctuation was greater. Menstrual cycle phase, by contrast, influenced general levels of heart-rate and mood, but did not affect responsivity to stress or performance. These findings suggest that the menstrual cycle and physical exercise have independent effects on cardiovascular and emotional state.

Diurnal sleep/wake-related immune functions during the menstrual cycle of healthy young women

Animal and human studies have related the sleeping/waking brain to the immune system. Because women are more susceptible to certain immunological illnesses, and sex steroids regulate immune functions, it was investigated whether the diurnal sleep/wake pattern of aspects of cellular immune functions and interleukin-1 (IL-1) and IL-2-like activities differed during low and high progesterone phases of the menstrual cycle. Eleven healthy women, mean age 24 y, were assessed over 24 h with serial venous blood samples. Peripheral blood monocytes were assayed for mitogen responses, i.e. phytohemagglutin (PHA) and pokeweed (PWM) and natural killer (NK) cell activities. Plasma was assayed for IL-1 and IL-2-like activities, cortisol and progesterone. Data were standardized by Z transformation and analysed by repeated-measures analysis of variance by comparing high (N = 5) vs. low (N = 6) progesterone phases. During the high progesterone phase, delayed slow-wave sleep (SWS) onset time and reduced amount of SWS was accompanied by a delay in the decline of NK cell activity, but rise in PHA activity following sleep onset. With the low progesterone phase, the pattern was similar to men with an early sleep decline in NK cell and late sleep rise in PHA activities. PWM rose during the night and plasma IL-1-like activity peaked during midday and during nocturnal sleep irrespective of the amount of progesterone. Slow-wave sleep and sleep-related NK cell and PHA activities differed over the menstrual cycle, but not PWM response. Increases in plasma IL-1 functions during midday and night are consistent with predisposition to sleepiness during these times.

Stressors, stress and stress consequences during long-duration manned space missions: a descriptive model

Keeping crew members in good health is a major factor in the success or failure of long-duration manned space missions. Among the many possible agents that can affect the crew's general well-being, stress is certainly one of the most critical because of its implications on human health and performance, both physical and mental. Nevertheless, very few studies have been performed on this fundamental issue and none of them has addressed it in its entirety, considering its diverse physical and psychological aspects. In this work, a descriptive model is proposed to expound the mechanism and sequence of events which mediate stress. A critical analysis of the information provided by past manned spaceflights and by dedicated research performed in analogous environments is presented, and an extrapolation of the available data on human stress in such extreme conditions is proposed. Both internal and external stressors have been identified, at physical and psychosocial levels, thus providing the basis for their early detection and preventive reduction. The possible negative consequences of stress that may lead to disease in crewmembers are described. Finally, the most effective instruments which may be of help in reducing space-related human stress and treating its negative consequences are suggested.

Power spectral analysis of heart rate variability in healthy young women during the normal menstrual cycle

This study investigated the fluctuations of autonomic nervous activities during the menstrual cycle. Twenty college females were tested for cardiovascular reactivity to mental challenge during both follicular and luteal phases across two menstrual cycles. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. At baseline, although heart rate and blood pressure did not differ across the menstrual cycle, the low-frequency (LF) component in the HRV was higher and the high-frequency (HF) component in the HRV was lower during the luteal phase than during the follicular phase. The LF/HF ratio was also significantly greater in the luteal phase. These data suggest that sympathetic nervous activities are predominant in the luteal phase as compared with follicular phase. In addition, the power spectral analysis of HRV has more sensitivity than heart rate or blood pressure in assessing the slight fluctuations of autonomic nervous activities during the menstrual cycle.

Acute psychological stress and epinephrine infusion in normolipidemic and hyperlipidemic men: effects on plasma lipid and apoprotein concentrations

This study examined whether psychological stress and the infusion of epinephrine increase plasma lipid and apoprotein concentrations in normolipidemic and hyperlipidemic men. Subjects were studied during three separate 6-hour laboratory sessions: a control session, during which subjects rested quietly while blood samples and hemodynamic measurements were obtained; a stress session, during which subjects were presented with two challenging mental tasks, followed by quiet rest; and an epinephrine infusion session, during which subjects received a low-dose infusion of epinephrine followed by quiet rest. The stress and epinephrine infusion manipulations produced the expected changes in plasma epinephrine and norepinephrine levels, blood pressure, and heart rate. Free fatty acid concentration increased markedly during epinephrine infusion and less dramatically but consistently during mental stress. Both stress and epinephrine infusion produced acute increases in plasma total, low-density lipoprotein, very low-density lipoprotein, and high-density lipoprotein cholesterol and apoprotein B concentrations, but comparable increases during the control session were not observed. Changes in albumin concentration (an index of plasma volume) were associated with changes in lipid concentrations during psychological stress. Epinephrine increases during psychological stress were correlated with increases in free fatty acid and triglyceride levels both during and after task administration. It was concluded that psychological or pharmacological stress induced in the laboratory produces changes in lipid concentrations, which at least during psychological stress, may be attributed to concomitant changes in plasma volume. The association between task-induced changes in epinephrine and changes in free fatty acid and triglyceride levels, also supports the hypothesis that psychological stress increases lipolysis.