Attenuated cortisol reactivity to psychosocial stress is associated with greater visual dependency in postural control.

Despite known anatomical links between the hypothalamic-pituitary-adrenal (HPA) axis and the vestibular system, there are no studies on the relationship between postural control and HPA axis function. Visual dependence in postural control, often measured by increased postural sway on exposure to visual motion, is an indication of altered visual-vestibular integration with greater weighting towards visual cues for balance. Visual dependence is more common in older age and a range of vestibular and non-vestibular health conditions. The relationship between visual dependence in postural control was investigated in relation to cortisol reactivity to psychosocial stress (using the Trier Social Stress Test for groups: TSST-G), as an index of HPA axis function, in healthy young females. In those who exhibited a cortisol response (>2 nmol/l), a negative relationship between stress-induced cortisol reactivity and visual dependence in postural control was observed, since those with the largest cortisol response showed less visual motion induced postural sway (measured by force platform). This finding in healthy females indicates that subtle non-clinical differences in vestibular function are associated with dysregulated HPA axis activity as indicated by lower cortisol reactivity to psychosocial stress. It adds to the growing body of evidence linking blunted cortisol reactivity to stress to poor homeostatic regulation and potential negative health and behavioural outcomes.

Salience versus magnitude in the measurement of the cortisol awakening response.

Pulsatile ultradian secretion of cortisol, rarely studied in salivary data, has functional importance in hypothalamic pituitary adrenal (HPA) axis regulation. The first daily ultradian episode, the cortisol awakening response (CAR), was examined in healthy adults, in 5-min secretion rates of salivary cortisol from electronically monitored awakening time to 1.25 h. Aggregated rates revealed a cubic trend, with wave-length of almost exactly 1 h, as predicted from known ultradian periodicity. Peak secretion rate occurred 20-min post-awakening. Peak (20-min) to trough (59-min) amplitude (PTA) expressed a salient signal shape. Rates rose steeply to and from peak, and major secretion was packaged into a few 5-min intervals, inconsistent with normal or uniform distribution of 5-min rates, but consistent with known pulsatile cortisol delivery. Null hypotheses asserting normal or uniform distributions were rejected. Maximal rates overwhelmingly occurred before and minimal rates after 30-mins, with degree of extremity at each polarity significantly positively correlated. To demonstrate utility and reliability of PTA estimation in a clinically relevant domain, re- analyses of a previously published study were conducted. Data from only three saliva samples were used, given importance of cost considerations for many CAR researchers. Difference between mean rates before and after 30-min yielded a simple salience index, highly correlated with PTA derived from full 5-min interval data. CAR salience performed significantly better than traditional AUCi magnitude in discriminating control cases (higher inferred amplitude) and cases with Seasonal Affective Disorder (lower inferred amplitude). Evidence suggested that low AUCi may be more sensitive in identifying within-subject changes (e.g. more depressed mood in winter among SAD cases) and low CAR salience better at revealing enduring between-subjects associations (e.g. underlying disorder vulnerability). Since both PTA salience and AUCi magnitude can be analysed and compared using exactly the same data from the same commonly used saliva sampling points, further research is warranted into the importance of individual differences in patterns of cortisol delivery, not just how much is delivered.

Repressors exhibit lower cortisol reactivity to group psychosocial stress.

Repressors are well-known to monitor potential psychosocial threats to their self-esteem and self-concept. In research, repressors are traditionally categorised as those scoring low on trait anxiety and high on defensiveness (as measured by social desirability scales). Examining repressors' cortisol reactivity to a group socio-evaluative laboratory stressor could be an important way to extend work on the classic 'repressor dissociation', which proposes that this group experience higher levels of physiological stress, but lower levels of subjective affect, during stressful situations. Research however has focused mainly on repressors' higher, more risk-prone levels of autonomic, rather than hypothalamic-pituitary-adrenal (HPA), reactivity to stressful stimuli. We assessed cortisol reactivity using a group-based acute psychosocial stressor, the Trier Social Stress Test for groups (TSST-G), which required participants to individually perform public speaking and mental arithmetic tasks in front of up to six other group members, as well as an evaluative panel of judges. Seventy-seven healthy young females (mean age ± SD: 20.2 ± 3.2 years) took part, of which 64 met the conventional criterion for a response to the TSST-G (<15.5% increase from baseline sample). The Stress-Arousal Checklist was completed pre- and post-TSST-G. Participants also completed the Perceived Stress Scale, the Trait Anxiety Inventory and the Marlow-Crowne Social Desirability Scale. The latter two measures were used to provide a categorisation of repressive coping style. Participants identified as repressive copers exhibited significantly lower cortisol reactivity during the TSST-G. Repressors also self-reported less subjective stress. These findings provide some evidence against the notion of the repressor dissociation and are discussed in terms of how cortisol hyporeactivity may be a pathway through which repressive coping adversely affects health.

Does the diurnal cycle of cortisol explain the relationship between physical performance and cognitive function in older adults?

BACKGROUND: Regular physical activity is a promising strategy to treat and prevent cognitive decline. The mechanisms that mediate these benefits are not fully clear but physical activity is thought to attenuate the harmful effects of chronic psychological stress and hypercortisolism on cognition. However, the circadian pattern of cortisol secretion is complex and it is not known which aspects are most closely associated with increased cognitive function and better physical performance. This is the first study to simultaneously measure cognitive function, the diurnal cycle of salivary cortisol and physical performance in older adults, without cognitive impairment (n = 30) and with amnestic Mild Cognitive Impairment (aMCI) (n = 30). RESULTS: Regression analysis showed that better cognitive function was associated with better physical performance. A greater variance in cortisol levels across the day from morning to evening was associated with better cognitive function and physical performance. CONCLUSIONS: The results support the idea that a more dynamic cortisol secretion pattern is associated with better cognitive function and physical performance even in the presence of cognitive impairment, but our results could not confirm a mediating role in this relationship.

The biological impact of living with chronic breathlessness - a role for the hypothalamic-pituitary-adrenal axis?

Breathlessness is a common and distressing symptom in advanced cardiorespiratory disease, with recognised psychological, functional and social consequences. The biological impact of living with chronic breathlessness has not been explored. As breathlessness is often perceived as a threat to survival, we propose that episodic breathlessness engages the stress-response, as regulated by the hypothalamic-pituitary-adrenal (HPA) axis. Furthermore, we hypothesise that chronic breathlessness causes excessive stimulation of the HPA axis, resulting in dysfunctional regulation of the HPA axis and associated neuropsychological, metabolic and immunological sequelae. A number of observations provide indirect support for this hypothesis. Firstly, breathlessness and the HPA axis are both associated with anxiety. Secondly, similar cortico-limbic system structures govern both breathlessness perception and HPA axis regulation. Thirdly, breathlessness and HPA axis dysfunction are both independent predictors of survival. There is a need for direct observational evidence as well as experimental data to investigate this hypothesis which, if plausible, could lead to the identification of a new biomarker pathway to support breathlessness research.

Increased cortisol levels in hair of recent Ecstasy/MDMA users.

Previous research has revealed an acute 8-fold increase in salivary cortisol following self-administrated Ecstasy/MDMA in dance clubbers. It is currently not known to what extent repeated usage impacts upon activity of the hypothalamic-pituitary-adrenal axis over a more prolonged period of time. This study investigated the integrated cortisol levels in 3-month hair samples from recent Ecstasy/MDMA users and non-user controls. One hundred and one unpaid participants (53 males, 48 females; mean age 21.75 years) completed the University of East London recreational drug use questionnaire, modified to cover the past 3-months of usage. They comprised 32 light recent Ecstasy/MDMA users (1-4 times in last 3 months), 23 recent heavy MDMA users (+5 times in last 3 months), and 54 non-user controls. Volunteers provided 3 cm hair samples for cortisol analysis. Hair cortisol levels were observed to be significantly higher in recent heavy MDMA users (mean = 55.0 ± 80.1 pg/mg), compared to recent light MDMA users (19.4 ± 16.0 pg/mg; p=0.015), and to non-users (13.8 ± 6.1 pg/mg; p<0.001). Hence the regular use of Ecstasy/MDMA was associated with almost 4-fold raised hair cortisol levels, in comparison with non-user controls. The present results are consistent with the bio-energetic stress model for Ecstasy/MDMA, which predicts that repeated stimulant drug use may increase cortisol production acutely, and result in greater deposits of the hormone in hair. These data may also help explain the neurocognitive, psychiatric, and other psychobiological problems of some abstinent users. Future study design and directions for research concerning the psychoneuroendocrinological impact of MDMA are also discussed.

Differences between diurnal patterns of salivary cortisol and dehydroepiandrosterone in healthy female adolescents.

The adrenal hormones cortisol and dehydroepiandrosterone (DHEA) share a common secretagogue: adrenocorticotropic hormone; however, secretion of these hormones can be dissociated suggesting subtle individual regulation at the level of the adrenal gland. We examined differences in the diurnal patterns of cortisol and DHEA secretion in healthy adolescent girls, with the aim of informing the possibility of exploiting these differences to aid interpretation of data from clinical populations in which these patterns can become dysregulated. Fifty-six healthy females aged 10-18 years provided saliva samples at 0 and 30 min (morning samples) and 12 h post-awakening on 2 consecutive weekdays. For morning salivary cortisol in relation to morning DHEA concentrations, correlational analysis revealed only a trend (p = 0.054). Similarly, the association between evening cortisol and DHEA was characterised as a trend (p = 0.084). Mean morning DHEA concentrations showed more day-to-day consistency than equivalent cortisol samples (r = 0.829 for DHEA and 0.468 for cortisol; z = 3.487, p < 0.0005). Unlike the cortisol pattern, characterised by a marked awakening response (cortisol awakening response, CAR), a significant rise in DHEA concentration post-awakening was not evident. Finally, there was a strong association between morning and evening concentrations of DHEA, not found for cortisol. The study shows differences in cortisol and DHEA secretion in the post-awakening period and informs work that seeks to examine correlates of dysregulated hypothalamic-pituitary-adrenal axis function. Parallel examination of both hormones enables enhanced interpretation of aberrant patterns of the CAR, i.e. an exploration of whether dysregulation affects both hormones (reflecting overall steroidogenic capacity) or cortisol alone (CAR-specific mechanisms).

Does physical activity reduce risk for Alzheimer's disease through interaction with the stress neuroendocrine system?

Lack of physical activity (PA) is a risk factor for Alzheimer's disease (AD), and PA interventions are believed to provide an effective non-pharmacological approach for attenuating the symptoms of this disease. However, the mechanism of action of these positive effects is currently unknown. It is possible that the benefits may be at least partially mediated by the effects on the neuroendocrine stress system. Chronic stress can lead to dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, leading to aberrant basal and circadian patterns of cortisol secretion and a cascade of negative downstream events. These factors have been linked not only to reduced cognitive function but also increased levels of amyloid-ß plaques and protein tau "tangles" (the neuropathological hallmarks of AD) in the non-demented mouse models of this disease. However, there is evidence that PA can have restorative effects on the stress neuroendocrine system and related risk factors relevant to AD. We explore the possibility that PA can positively impact upon AD by restoring normative HPA axis function, with consequent downstream effects upon underlying neuropathology and associated cognitive function. We conclude with suggestions for future research to test this hypothesis in patients with AD.

The diurnal cortisol cycle and cognitive performance in the healthy old.

Associations between cognitive performance and cortisol have variously been reported for measures of both cortisol level and change, and for some domains of cognitive functioning more than others. In this study, associations between cortisol secretion measures and cognitive performance were examined in 50 healthy older people (mean age 74 years; 34 F /16 M). Participants provided 16 accurately timed saliva samples over 2 consecutive days to determine diurnal profiles of cortisol secretion. Overall cognitive performance (OCP) was measured as the principal component of a comprehensive battery of cognitive tests. Across a 30 year age range, there was a strong inverse correlation between age and OCP. Age and poorer OCP were also associated with an attenuated cortisol awakening response (CAR), defined as the rise from 0-30 min after awakening, and a subsequent less steep fall in cortisol level over the rest of the day. Partialling analyses, suggested that the correlation between fall in cortisol over the day and OCP was independent of age. Both older age and less cortisol change were particularly related to poorer performance on tests of declarative memory and executive functioning. Our conclusions are that during the short post-awakening period, an exception exists to the generally pertaining association between higher levels of cortisol and poorer cognitive performance. Consequentially dynamic measures reflecting the rise (CAR) and fall from the post-awakening peak may be particularly salient in helping to explain links between cortisol and cognitive performance. Finally our pattern of results across different cognitive tests suggests an association between cortisol and those domains of cognitive functioning which depend crucially on the integrity of the hippocampus and pre-frontal cortex.

Diurnal patterns of salivary cortisol across the adolescent period in healthy females.

When examining the diurnal profile of the hormone cortisol in children and adolescents developmental issues are particularly relevant. Previous findings regarding relationships between cortisol secretory activity and reproductive (pubertal) maturation lack clarity and may reflect methodological inconsistencies between studies. This study examined the diurnal cortisol profile across female adolescence, with a particular focus on an obvious and unique marker of development: menarche. In a cross-sectional design, 61 healthy female adolescents aged 9-18 years (mean age 13.89 years, S.D.+/-2.72) collected eight saliva samples per day on two consecutive weekdays. Samples were collected at awakening, 15, 30 and 45min and 3, 6, 9 and 12h post-awakening in order to capture both the cortisol awakening response (CAR) and the subsequent period of decline. Demographic information was recorded and participants also completed the Spielberger State-Trait Anxiety Inventory. Patterns of cortisol secretion exhibited good intra-individual stability across the two sampling days. Participants evidenced a robust diurnal pattern, with cortisol levels peaking approximately 30-45min post-awakening (the CAR) and steadily declining concentrations over the remainder of the day. Differences according to developmental status (in terms of whether or not participants had experienced first menses: menarche) were observed in the time of peak secretion of the CAR, and these distinct patterns could not be accounted for by group differences in demographic, situational or psychological characteristics measured in this study. This effect for the CAR was associated with the onset of menarche alone, unlike cortisol levels over the remainder of the day. For those who had undergone menarche, were older and of greater BMI, cortisol levels remained higher over the day. There was a significant difference in cortisol concentrations at 6h post-awakening between pre- and post-menarche groups. Again, these differences in daytime cortisol secretory activity could not be attributed to situational or psychological factors. Establishing patterns of cortisol secretion in healthy female adolescents provides an important baseline from which to investigate hypothalamic-pituitary-adrenal (HPA) physiology, measured via salivary cortisol, in adolescent populations with known or suspected psychopathology.

Cortisol secretory activity in older people in relation to positive and negative well-being.

Secretion of the hormone cortisol, a physiological correlate of affect, has been studied mostly in relation to negative states, especially stress. By contrast, policy initiatives aimed at older populations now routinely emphasise well-being and a 'positive ageing' perspective. In this study, we examined diurnal salivary cortisol profiles from 50 active seniors recruited into a wider community research project (mean age 74 years; 34 F/16 M). Participants' wrist activity was continuously monitored by actimeters in their homes over a 48 h period. During this time two diurnal cycles of cortisol data were collected (8 samples per day); with actimeter data providing a compliance check in regard to timing of self-administered saliva collections. Prior to the trial, participants had completed the GHQ-30 which was scored separately to yield both positive and negative well-being scores which matched closely normative data from over 6000 cases in a large survey. Our data suggest that positive and negative psychological well-being are quite strongly and inversely correlated. However, neither on their own was associated with basal levels of cortisol. Rather, for cortisol secretion in the 45-min period following awakening, but not during the rest of the day, we found a significant interaction between positive and negative well-being (p<0.024). Further analysis of this interaction showed that among participants low on negative well-being, higher positive well-being was significantly associated with lower cortisol; equally, among participants high on positive well-being, lower negative well-being was significantly associated with lower cortisol. Thus, a powerful synergy seemed to be operating in this early morning period such that cortisol secretion was 27% lower in participants with both higher-than-average positive well-being and lower-than-average negative well-being (comprising 34% of the sample). We conclude that cortisol secretion in the first 45 min following awakening is distinct from the rest of the day and most able to discriminate well-being states.

Suspected non-adherence and weekend versus week day differences in the awakening cortisol response.

The pronounced rise in cortisol following awakening holds promise as a bio-marker of variables in the psychosocial domain, but its investigation also presents methodological challenges, which we attempted to address in this study. Forty-eight healthy, young students participated and were instructed to collect saliva 0, 15, 30 and 45 min post awakening on two consecutive normal weekdays and two consecutive weekend days (order counterbalanced). Participants' awakening cortisol response (ACR) profiles differed between the weekdays and weekend with trend analysis revealing a steeper rise on weekdays compared to the weekend. These differences were not accounted for by weekday/weekend differences in awakening time and state stress or by perceived stress over the previous month. Total salivary-free cortisol secretion (area under the cortisol curve (AUC)) over the 4 study days was negatively correlated with the measure of longer term stress and awakening time. The mean 4-day rise in cortisol (mean increase: MnInc) was also negatively correlated with awakening time. This awakening time effect was not mediated by stress or vice versa, since both were independent predictors of cortisol. In an attempt to address the ubiquitous problem of non-adherence to the requested saliva sampling regime, known to distort the shape of the ACR, suspected non-adherence (SNA) was examined by identifying instances of profiles showing no cortisol rise from the waking sample to either the 15 or 30 min sample post awakening. Analysis controlling for SNA status had no effect upon the observed associations with Perceived Stress Scale (PSS) and awakening time however it abolished the otherwise highly significant flatter profile at weekends.

Post-awakening cortisol secretion during basic military training.

Salivary free cortisol concentrations in the first 30 min after awakening were assessed in 12 healthy army recruits at the beginning, middle and end of an 11-week intensive physical training course. To ensure strict adherence to protocol saliva collection was supervised and collected on each sampling day immediately on waking and again 15 and 30 min later. Self-rated psychological assessments of state levels of stress, arousal and fatigue were performed in the evening of each sampling day. A within-subjects repeated-measures analysis of participants who completed the course (12 of the original 20) showed a significant main effect of cortisol concentration across all three sampling points after awakening (F((2,22))=54.516, p<0.0001) and a significant main effect of weeks into the training course (F((3,33))=4.390, p=0.010). Further analysis of this effect of measurement-week revealed that at weeks 3 and 6 total cortisol secretion estimated by area under the curve was lower (F((3,33))=4.602, p=0.008) compared to the beginning and end of the course. Surprisingly self-reported stress, arousal and fatigue did not differ significantly across weeks, despite the large dropout rate (40%) and self-evident pressures of the course. We conclude that when controlling for many confounding variables, including participant adherence, post-awakening cortisol levels are sensitive to stressful challenge over a period of weeks.

The diurnal patterns of the adrenal steroids cortisol and dehydroepiandrosterone (DHEA) in relation to awakening.

The steroid hormones, cortisol and dehydroepiandrosterone (DHEA) are the two main peripheral secretory products of the hypothalamic-pituitary-adrenal stress-neuroendocrine axis. The diurnal pattern of cortisol secretory activity has been well characterised. Various aspects of this pattern have been related to time of awakening, light exposure, psychological dimensions of affect, immune function and systemic health and well-being. DHEA is also an important adrenocortical steroid whose secretory activity has been related to immune function, psychological and health variables. The most pronounced feature of the diurnal cortisol cycle is a burst of secretory activity following awakening with a diurnal decline thereafter. We mapped DHEA secretory activity onto this cycle by measuring both steroids in saliva samples collected at distinct time points over the diurnal cycle, synchronised to awakening. Both steroids, particularly DHEA, showed stability across days of sample collection. A main distinction between cortisol and DHEA was that although DHEA was elevated in post-awakening samples compared with later in the day there was no evidence of an awakening stimulatory burst of DHEA secretory activity. Although DHEA in many respects paralleled cortisol secretory activity there was some dissociation; mean levels were positively but not tightly correlated. The secretory pattern of DHEA is very stable whereas cortisol secretory activity seems more sensitive to day-to-day variability.

The effect of dawn simulation on the cortisol response to awakening in healthy participants.

Bright light exposure after awakening has been shown to elevate cortisol levels in healthy participants. The present study examined the effect of dawn simulation (a treatment for seasonal affective disorder) on the cortisol response to awakening and mood. Twelve healthy participants were supplied with a dawn simulator (The Natural Alarm Clock, Outside In, Cambridge Ltd), a bedside light that increases in intensity prior to awakening to approximately 250 lux over 30 mins when an audible alarm sounds. A counterbalanced study was performed on 4 consecutive normal weekdays, two of which were control days (no dawn simulation) and two experimental (dawn simulation). Saliva samples were taken immediately on awakening then at 15, 30 and 45 minutes post awakening on all 4 study-days. Total cortisol production during the first 45 mins after awakening was found to be significantly higher in the experimental condition than in the control condition. Participants also reported greater arousal in the experimental condition and there was a trend for an association between increased arousal and increased cortisol secretory activity under dawn simulation. This study provides supportive evidence for the role of light and the suprachiasmatic nucleus in the awakening cortisol response.

The awakening cortisol response: methodological issues and significance.

The awakening cortisol response (ACR) is a discrete and distinctive part of the cortisol circadian cycle. In healthy adults salivary free cortisol concentrations increase by between 50 and 160% in the first 30 min immediately post-awakening (approximate average increase of 9 nmol/l, range 4-15 nmol/l, estimated to be equivalent to about three secretory episodes). However there are no agreed norms for the absolute concentrations of free cortisol in saliva either immediately post-awakening (range of 4.7-18.5 nmol/l) or 30 min post-awakening (range of 8.6-21.9 nmol/l). This review explores reasons for these discrepancies in normative data including confounding factors such as gender, age, awakening time, light and participant adherence. Although the physiological role of the ACR has not been clearly defined evidence is discussed that suggests it is under a distinct regulatory influence, different from the rest of the diurnal cortisol secretory cycle. Despite the difficulties associated with its measurement a range of studies have demonstrated an association between the ACR and psychosocial variables, stress and health. However it remains unclear whether positive affect and good health are consistently associated with larger or smaller awakening responses. It is early days in the search for the role and significance of the ACR. Its putative role in the regulation of physiological function across the day (e.g. the immune system) and its sensitivity to psychosocial variables make it a prime candidate as an intermediary linking mind and health.

The awakening cortisol response: no evidence for an influence of body posture.

It has recently been reported that the orthostatic challenge associated with postural change from sitting to an upright position is stimulatory to the hypothalamic-pituitary-adrenal axis as evidenced by increased salivary free cortisol. This stimulatory influence is potentially a confound for the many psychoneuroendocrine studies for which salivary free cortisol is the main dependent variable. This particularly relates to laboratory psychosocial stress procedures in which subjects are invited to stand in order to deliver public speech and the studies which have explored the cortisol response to awakening in which postural shift has not been controlled for. We therefore examined, in a balanced cross over design whether the awakening cortisol response was influenced by standing, shortly after awakening or remaining supine during the response study period. In addition and in the same subjects we measured the cardiovascular response and saliva cortisol response to the orthostatic challenge of shifting from a supine to a standing position later in the diurnal cortisol cycle. The expected cortisol response to awakening was demonstrated but there was no evidence that the postural shift, supine to standing, confounded the response. This same postural shift later in the day induced the expected increase in heart rate but cortisol simply followed the circadian decline. Under the conditions of the present study we found no evidence that the postural shift supine to standing could induce a cortisol secretory episode such as to contribute towards the awakening response.

Ultrasound measures of bone and the diurnal free cortisol cycle: a positive association with the awakening cortisol response in healthy premenopausal women.

In this study we examined the relationship between characteristics of the diurnal pattern of salivary free cortisol concentration and ultrasound (US) measures of bone in premenopausal women. Subjects were 36 healthy, eumenorrhoeic, nonsmoking women mean age (SE) 30.9 (1.3) years. Saliva samples were collected on awakening and 10, 20, 30, 120, 240, and 600 minutes thereafter. Calcaneal broadband ultrasonic attenuation (BUA) and speed of sound (SOS) were determined. Mean (SE) salivary cortisol concentration was 4.7 (0.5) nmol/l on awakening, peaked at 8.6 (0.9) nmol/l 30 min later, and declined to a trough of 2.3 (0.2) nmol/l 600 min after awakening. BUA and SOS were significantly associated with cortisol 0 and 30 min after awakening (r = 0.40 and 0.40 for BUA and 0.33 and 0.37 for SOS, respectively, with body mass included as covariate). Cortisol levels 240 and 600 min after awakening were not significantly associated with bone variables. Women above the median for peak (30 min after awakening) cortisol had significantly higher BUA and SOS than those below the median [BUA 51.8 (1.0) vs 47.4 (1.5) dB/MHz, P = 0.017; SOS 1554.0 (2.5) vs 1546.4 (1.5) m/sec, P = 0.008]. A high peak in cortisol following awakening was associated with higher US measures of bone in healthy premenopausal women. This finding suggests the possibility that diurnal variation in cortisol may have a role in bone metabolism.

The impact of psychological stress on immune function in the athletic population.

In many ways, the physiological and immune consequences of acute bursts of physical exercise parallel the effect of an acute psychological stressor. Similarly, the net effects of endurance training resemble chronic psychological stress, whereas the physiological milieu associated with overtraining resembles that of melancholic depression. We suggest that the prolonged psychological stress often associated with athletic training and competition may make athletes more vulnerable to the negative health effects of training. Furthermore, a relationship between anxiety and life events on susceptibility to injury is well documented. Individual differences in self-confidence and self-esteem are also known to relate to the occurrence of injury as well as recovery from injury. We suggest that these two observations may be linked. It is the purpose of this paper to review the most recent evidence that psychological stress does impact upon the balance of the immune system in such a way as to be relevant to health outcomes and that the athletic population, in particular those with low self-esteem, may be especially vulnerable due to the probable synergistic effects of both physical and psychological stress.

Association between time of awakening and diurnal cortisol secretory activity.

A 12-hour diurnal profile of salivary free cortisol was measured in healthy adults (n=40) on two consecutive days. Samples were collected at timed intervals synchronised to awakening. The mean profile is characterised by a marked increase in cortisol concentration following awakening, peaking after about 30 min, and a subsequent decline over the remainder of the day. Thus two components of the diurnal cycle were examined: a) the first 45 min post-awakening (the awakening cortisol response) and b) the underlying 12 h profile from immediately until 12 h post awakening (but without the awakening response). Both of these components were analysed in two ways such as to provide an indication of overall cortisol concentration and the degree of change in cortisol concentration, i.e. the rise for the awakening response and the diurnal decline. Both components of the cortisol diurnal profile were negatively correlated with awakening time. Thus, those subjects who awoke earliest had higher levels of cortisol over the 45 min following awakening as well as throughout the rest of the day. They also displayed a more marked diurnal decline to be convergent with late awakeners at the end of diurnal measurement, 12 h following awakening. Hence the diurnal cortisol cycle, which is synchronised to awakening, is significantly related to awakening time. These findings support the notion of a close association between suprachiasmatic nucleus (SCN) control of both awakening and cortisol secretory activity.