G72 and its association with major depression and neuroticism in large population-based groups from Germany

OBJECTIVE

G72 is among the most frequently replicated vulnerability genes for schizophrenia and bipolar disorder. The authors previously found identical haplotypes of markers M23 and M24 to be associated with schizophrenia, bipolar disorder, and panic disorder. Given both the well-recognized familial clustering across these disorders and recent linkage findings implicating the region harboring G72 in the etiology of major depression and panic disorder, we can hypothesize that G72 should also be involved in the etiology of major depression. Neuroticism, measuring trait anxiety, may be the endophenotypic link underlying genetic associations with G72 across diagnostic boundaries. The authors tested whether the previously observed risk haplotypes are also associated with major depression and neuroticism.

METHOD

The authors performed a standard haplotype analysis in a group of 500 major depression patients and 1,030 population-based comparison subjects. The authors also performed an exploratory analysis on 10 additional G72 markers using a novel haplotype-sharing approach. They performed a quantitative trait haplotype analysis in an independent group of 907 individuals phenotyped for neuroticism.

RESULTS

The previously identified M23-M24 risk haplotype was significantly associated with major depression and high levels of neuroticism. The haplotype-sharing analysis also implicated the same region, whereas more proximal markers showed no association with major depression.

CONCLUSIONS

This is the first study to the authors' knowledge to implicate the G72 locus in the etiology of major depression and neuroticism. The results strengthen the notion of a genetic overlap between diagnoses, commonly conceptualized as distinct entities. Neuroticism may constitute the common underlying endophenotypic link.

Sex specific associations between common glucocorticoid receptor gene variants and hypothalamus-pituitary-adrenal axis responses to psychosocial stress

BACKGROUND

Alterations in glucocorticoid (GC) signaling have been associated with a number of psychiatric disorders. Genetic variation of the glucocorticoid receptor (GR) might be one of the factors underlying susceptibility to stress related disease.

METHODS

We investigated 206 healthy subjects and assessed associations between four common GR gene (NR3C1) polymorphisms (ER22/23EK, N363S, BclI, 9beta) and hypothalamic-pituitary-adrenal (HPA) axis responses to psychosocial stress (Trier Social Stress Test, TSST) and glucocorticoid sensitivity measured by a dexamethasone suppression test (DST).

RESULTS

Male 9beta AG carriers displayed the highest adrenocorticotropic hormone (ACTH) and total cortisol TSST responses (for ACTH: main effect genotype p = .02) whereas male BclI GG carriers showed diminished responses. Remarkably, the BclI GG genotype in women (all using oral contraceptives) was associated with the highest total cortisol TSST responses, resulting in a significant sex by genotype interaction (p = .03). Following the DST, male 9beta AG carriers had elevated ACTH levels (sex by genotype interaction p = .03).

CONCLUSIONS

We observed significant sex specific associations between GR gene polymorphisms and HPA axis responses to psychosocial stress as well as GC sensitivity. These findings support the relevance of GR gene polymorphisms in HPA axis regulation. Genetic variations of the GR might constitute a risk factor in development of HPA axis related disorders.

Cortisol and ACTH responses to psychosocial stress are modulated by corticosteroid binding globulin levels

The hypothalamus-pituitary-adrenal (HPA) axis is vital for an organisms' response to physiological and psychological stress. Cortisol, secreted upon activation of the HPA axis, impacts on physiological systems throughout the organism. Responses to cortisol are influenced and modified by a number of factors, including corticosteroid binding globulin (CBG) levels. A major part of circulating cortisol is bound to CBG and only the unbound fraction is thought to be biologically active. The aim of the present study was to examine the modulating effect of CBG levels on hormonal responses following psychosocial stress in women using oral contraceptives (n=115) and in medication-free men (n=93). In women, CBG levels were negatively associated with ACTH and salivary cortisol and positively with total cortisol levels following the TSST. In men, positive associations were observed between CBG and ACTH and total cortisol levels following the TSST. CBG is an important regulatory element of HPA axis response patterns; therefore, CBG levels have to be taken into account as a potential modifier of ACTH and cortisol responses to psychosocial and pharmacological stimulation. Investigations of the consequences of long-lasting OC intake on the neuroendocrine stress regulation in women might be warranted.

Is the cortisol awakening rise a response to awakening?

A distinct rise in cortisol levels that occurs after morning awakening is increasingly used as an indicator of adrenocortical activity which is associated with different pathologies. Although it was previously assumed that the transition from sleep to wake is essential for the occurrence of the cortisol morning rise, this has never been tested. Here, we examined 16 healthy young men (20-33 yrs) between 2300 and 0800 h under sleep laboratory conditions. Serum cortisol and plasma adrenocorticotropin (ACTH) as well as salivary cortisol levels (after subjects were woken up at 0700 h) were repeatedly assessed. In a supplementary study condition, salivary cortisol levels in the first hour after awakening were measured at the subjects' home on two consecutive days. Comparison of pre- and post awakening measurements revealed significantly steeper increases in cortisol and ACTH after awakening. The rise in cortisol upon awakening under laboratory conditions did not significantly differ from that observed at home. We conclude that the cortisol increase after awakening is a response to morning awakening that is distinct from the circadian rise in hypothalamo-pituitary-adrenal (HPA) activity in the morning hours. Although the cortisol awakening response is modulated by circadian influences, it primarily reflects phasic psychophysiological processes specific to the sleep-wake transition.

Circadian cortisol profiles and psychological self-reports in shift workers with and without recent change in the shift rotation system

Cortisol profiles including the cortisol rise in the first hour after awakening (CAR) were assessed during shift work and days off (eight saliva samples per shift). Participants were 102 healthy permanent day and night shift workers (comparison groups) and former permanent day and night shift workers after implementation of a new fast-forward rota including morning, evening, and night shifts. Results show that the CAR is detectable in day as well as night shifts. In permanent night workers cortisol profiles appear to be blunted during night work and days off. However, circadian cortisol profiles are not disturbed in former night workers who recently switched to the fast rotating shift schedule. In contrast, implementation of night work in former day workers seems to lead to initially blunted cortisol profiles that normalize after a short adjustment period. Results of a psychological assessment including exhaustion, chronic stress, effort-reward imbalance, and ratings of sleep quality and sleep length are also presented.

A common polymorphism in the mineralocorticoid receptor modulates stress responsiveness

CONTEXT

Mineralocorticoid receptors (MR) mediate the action of aldosterone on sodium resorption in kidney tubular cells, but in brain they respond to the glucocorticoid cortisol in stress regulation and cognitive processes.

OBJECTIVE

The objective of the study was to investigate the role of the MR gene variant I180V in the neuroendocrine response to a psychosocial stressor and in electrolyte regulation.

DESIGN

Associations between the MRI180V and outcome variables in a healthy cohort subjected to psychosocial challenge (Trier Social Stress Test) and in a mild hypertensive cohort exposed to acute salt loading (Weinberger's test) were investigated. In vitro transactivational assays were applied to compare the effects of cortisol and aldosterone on the MRI180V.

RESULTS

Carriers of the MR180V allele showed higher saliva (P < 0.01), plasma cortisol (P < 0.01), and heart rate responses (P < 0.05) to the Trier Social Stress Test than noncarriers (MR180I). After 3 d of a normal salt diet and the Weinberger's test, no association was found with urinary sodium excretion, plasma aldosterone, and plasma renin activity or with changes in blood pressure, aldosterone, and renin responses. In vitro testing of the MR180V allele revealed a mild loss of function using cortisol as a ligand, compared with the MR180I allele. Significantly higher doses of cortisol were needed for half-maximal induction on the TAT-1 (P < 0.002), TAT-3 (P < 0.03), or mouse mammary tumor virus (P < 0.02) promoters, whereas maximal induction was not different. These differences were not observed using aldosterone as a ligand.

CONCLUSION

The findings reveal that cortisol and heart rate responses to a psychosocial stressor are enhanced in carriers of the MR180V variant.

Morningness and eveningness: The free cortisol rise after awakening in “early birds” and “night owls”

We investigated salivary cortisol profiles in the first hour after awakening in morning versus evening chronotypes. Chronotypes were defined by Horne and Ostberg's Owl-and-Lark-Questionnaire. In a sample of 112 healthy, day-active young men, we identified 9 morning and 29 evening chronotypes. Saliva samples were collected 0, 30, 45, and 60min after awakening on 2 consecutive days. Log-transformed cortisol levels were analyzed with General Linear Model procedures (GLMs) and awakening time and sleep duration were entered as covariates. On both days, a significant main effect of chronotype emerged (both p=0.02), and this effect could not be explained by differences in awakening time or sleep duration. The present data support the idea that morning relative to evening chronotypes might show higher cortisol levels in the first hour after awakening. In sum, individual chronotype should be acknowledged as one further possible source of interindividual variability in the cortisol rise after awakening.

The heritability of perceived stress

BACKGROUND

Exploration of the degree to which perceived chronic stress is heritable is important as these self-reports have been linked to stress-related health outcomes. The aims of this study were to estimate whether perceived stress is a heritable condition and to assess whether heritability estimates vary between subjective stress reactivity and stress related to external demands.

METHOD

A sample of 103 monozygotic and 77 dizygotic twin pairs completed three questionnaires designed to measure perceived stress: the Perceived Stress Scale (PSS), the Measure for the Assessment of Stress Susceptibility (MESA) and the Trier Inventory for the Assessment of Chronic Stress (TICS). The TICS assesses the frequency of stressful experiences on six scales, the MESA assesses subjective stress reactivity, and the PSS takes both factors into account.

RESULTS

A multivariate model-fitting procedure revealed that a model with common additive genetic and shared environmental factors best fit the eight scales (PSS, MESA, six TICS scales). Heritabilities for the best-fitting model varied between 5% and 45%, depending on the scale.

CONCLUSIONS

The present data suggest that perceived stress is in part heritable, that nearly half of the covariance between stress scales is due to genetic factors, and that heritability estimates vary considerably, depending on the questionnaire. Beyond methodological considerations that pertain to the validity of the questionnaires, these data suggest that studies assessing the heritability of perceived chronic stress should take the specific questionnaire focus into account.

Parity does not alter baseline or stimulated activity of the hypothalamus-pituitary-adrenal axis in women

Pregnancy is associated with considerable physiological adaptations, some of which long outlast the state of pregnancy. Although it is well documented that pregnancy produces alterations of the hypothalamus-pituitary-adrenal axis, the longer-term effects of pregnancy on this system have not been systematically examined in humans. Subjects in the present study were 159 nulliparous and 265 parous women. Data analysis revealed no impact of parity on baseline activity (salivary cortisol: response to awakening, F </= .03, day profile: F </= 3.89, both n.s.). In a subsample, similar results were obtained for dexamethasone-suppressed salivary cortisol levels (all F </= 1.45 n.s., n = 45), as well as salivary cortisol, total cortisol, and ACTH responses to stimulation with a psychosocial stress protocol (all F </= .93 n.s., n = 47). These findings suggest that parity is not associated with long-term alterations of hypothalamus-pituitary-adrenal axis activity, and postpregnancy measures can, therefore, be used as proxy markers for a woman's prepregnancy status of this system.

Birth weight is associated with salivary cortisol responses to psychosocial stress in adult life

Fetal programming of the hypothalamus-pituitary-adrenal (HPA) axis was proposed as one mechanism underlying the link between prenatal stress, adverse birth outcomes (particularly low birth weight) and an enhanced vulnerability for several diseases later in life. In recent studies, birth weight was significantly related to basal cortisol levels as well as to cortisol responses to pharmacological stimulation. In order to investigate the association between cortisol responses to psychological challenge, birth weight and length of gestation, 106 young healthy males were exposed to the 'Trier Social Stress Test'. Salivary cortisol responses to the stress exposure were significantly and inversely related to the subjects' birth weight, while the analysis of the impact of gestational age yielded inconsistent results. This finding is consistent with the concept of fetal programming of the HPA axis and provides the first preliminary evidence for an association between birth weight and adrenocortical responses to psychosocial stress. As the investigated subjects were twins, possible implications of this sample characteristic for the present findings are discussed.

A psychobiological perspective on genetic determinants of hypothalamus-pituitary-adrenal axis activity

From the perspective of psychobiological stress research we present a brief overview of findings documenting a significant impact of genetic factors on the activity of the hypothalamus-pituitary-adrenal (HPA) axis. Quantitative genetic studies in twins as well as association studies, primarily on polymorphisms in the glucocorticoid receptor gene, are depicted. Recent findings suggest that the collaboration of psychobiology and molecular genetics is a promising interdisciplinary approach that will significantly contribute to the understanding of the mechanisms underlying the link between stress, the HPA axis, and HPA-related clinical states.

Habituation of cortisol responses to repeated psychosocial stress-further characterization and impact of genetic factors

Although a rapid response habituation to repeated stress exposure is a key characteristic of the hypothalamus-pituitary-adrenal (HPA) axis, several studies document a substantial inter-individual variability of such HPA response patterns. In order to further investigate the individual differences in the habituation of this important neuroendocrine system to psychosocial stress, 54 male twin pairs were exposed to moderate psychosocial stress on three occasions, each exposure separated by a 1-week interval. Additionally, an ACTH(1-24) stimulation test (1 microg) and a dexamethasone suppression test (0.5mg) were performed. Although on average the expected decrease of mean cortisol and ACTH responses across stress exposures was observed, only 52% of the subjects showed this well-documented general decline and almost 16% of the participants even showed a response sensitization across sessions. Furthermore, a weak habituation was related to low cortisol responses to both the first stress exposure as well as the ACTH challenge. Moreover, genetic analyses did not reveal any evidence for a substantial heritability of the individual cortisol response habituation or an association between this habituation and two common polymorphisms in the glucocorticoid receptor gene.

The heritability of hypothalamus pituitary adrenal axis responses to psychosocial stress is context dependent

Individual differences in the response of the hypothalamus pituitary adrenal axis to stress are known to play an important role in health and disease risk. The origins, or determinants, of these individual differences are not well understood. To date, no study has examined the effects of context on the heritability of psychoendocrine stress responses. In the present study, 58 male twin pairs were exposed to a psychosocial stressor (Trier Social Stress Test) three times at weekly intervals, and their salivary and total cortisol, ACTH, and heart rate responses were assessed. Modest heritabilities were observed for all measures at the first stress exposure (all h2 < 0.33), but heritability estimates increased substantially with repetition of the stressor (T3: all h2 > 0.97). Concurrently, only the first but not the second and third Trier Social Stress Test exposure induced a significant increase in state anxiety (T1: P < 0.01, T2 and T3: n.s.), suggesting low heritabilities in a new, anxiety-evoking context and high heritabilities in a familiar, low-anxiety context. These findings challenge previous reports on a low heritability of markers of stimulated hypothalamus pituitary adrenal axis activity and are the first to document the relevance of context for psychoendocrine heritability estimates.

Free cortisol awakening responses are influenced by awakening time

Psychobiological investigations on the hypothalamus-pituitary-adrenal (HPA) axis depend on markers that adequately describe the activity of this system. There is evidence that the free cortisol response to awakening, proposed as a marker for the HPA axis, can be influenced by time of awakening. To further investigate this possible confounder, 24 shift working nurses and 31 female students on a regular sleep-wake cycle collected saliva samples 0, 30, 45 and 60 minutes after awakening. Nurses were investigated on the first and second day of their early (awakening: 04:00-05:30 h), late (awakening: 06:00-09:00 h), and night shift (awakening: 11:00-14:00 h), respectively. Students were studied after taking a short nap on two consecutive weekdays (awakening: 18:45-20:30 h). Mean cortisol levels after awakening increased significantly under all three shift conditions (p<0.01), but decreased in the student sample (p<.05). Within the three shift conditions, cortisol responses following waking in the early shift were more pronounced than in late (p<.01) and night shift (p<.05). The present study shows that in a sample with a large range of awakening times, an impact of this variable on the cortisol awakening response can be observed. The data furthermore strongly suggest that waking up per se is insufficient for adrenocortical stimulation.

Common polymorphisms in the glucocorticoid receptor gene are associated with adrenocortical responses to psychosocial stress

Chronic dysregulation of hypothalamus-pituitary-adrenal axis activity is related to several stress-related disorders. Evidence suggests that polymorphisms in the glucocorticoid receptor (GR) gene may have an impact on this neuroendocrine system. In the present investigation, 112 healthy males were studied to estimate the impact of three GR gene polymorphisms (BclI RFLP, N363S, ER22/23EK) on cortisol and ACTH responses to psychosocial stress (Trier Social Stress Test) and pharmacological stimulation (1 microg ACTH(1-24), 0.5 mg dexamethasone). Because only four ER22/23EK heterozygotes were identified, these subjects were not statistically analyzed. Compared with subjects with the wild-type GR genotype (n = 36), 363S allele carriers (n = 10) showed significantly increased salivary cortisol responses to stress, whereas the BclI genotype GG (n = 18) was associated with a diminished cortisol response. BclI heterozygotes and homozygotes (GG) exhibited a trend toward lower ACTH responses, compared with wild-type subjects and 363S carriers. The cortisol response to ACTH(1-24) administration was not significantly different between genotypes. After dexamethasone ingestion, 363S carriers showed a trend toward an enhanced cortisol suppression. This is the first report documenting an impact of GR gene polymorphisms on cortisol (and perhaps ACTH) responses to psychosocial stress. These variants may contribute to the individual vulnerability for hypothalamus-pituitary-adrenal-related disorders.

The cortisol awakening response - normal values and confounds

In several recent investigations it could be demonstrated that the free cortisol response to awakening can serve as an useful index of the adrenocortical activity. When measured with strict reference to the time of awakening the assessment of this endocrine response is able to uncover subtle changes in hypothalamus-pituitary-adrenal (HPA) axis activity, which are, for instance, related to persisting pain, burnout and chronic stress. Furthermore, it has been suggested that the HPA axis might serve as an indicator of allostatic load in subjects exposed to prolonged environmental noise. In the present paper four separate studies with a total of 509 adult subjects were combined in order to provide reliable information on normal values for the free cortisol response to awakening. Corresponding with earlier findings, a mean cortisol increase of about 50% within the first 30 minutes after awakening was observed. The intraindividual stability over time was shown to be remarkably high with correlations up to r=.63 (for the area under the response curve). Furthermore, the cortisol rise after awakening is rather consistent, with responder rates of about 75%. Gender significantly influenced early morning free cortisol levels. Although women showed a virtually identical cortisol increase after awakening compared to men, a significantly delayed decrease was observed. Confirming and extending previous findings, the present study strongly suggests that neither age, nor the use of oral contraceptives, habitual smoking, time of awakening, sleep duration or using / not using an alarm clock have a considerable impact on free cortisol levels after awakening. The cortisol awakening response can be assessed under a wide variety of clinical and field settings, since it is non-invasive, inexpensive and easy-to-employ. The present data provide normal values and information on potential confounds which should facilitate investigations into the endocrine consequences of prolonged exposure to environmental noise.

Geschlechtsunterschiede bei stressbezogenen Variablen

Zusammenfassung: Obwohl Frauen durchschnittlich von mehr Befindensstörungen, Stress und körperlichen Beschwerden berichten als Männer, weist ihre höhere Lebenserwartung objektiv auf eine bessere Gesundheit hin. Zur Erklärung dieses paradoxen Befundes wird die interindividuell variierende Neigung zur Besorgnis herangezogen. In der Besorgnis-Skala des Trierer Inventar zur Erfassung von chronischem Stress (TICS) zeigt sich eine altersunabhängig stärker ausgeprägte Besorgnisneigung bei Frauen (N = 1255), die Geschlechtsunterschiede in anderen Skalen zum chronischen Stress aufklärt. In einer weiteren Stichprobe (N = 360) erklärt die Variable Besorgnisneigung Geschlechtsunterschiede bei stressbezogenen Variablen, die in der Literatur berichtet werden. Nach den hier vorgestellten Ergebnissen lassen sich die durchschnittlich höheren Werte von Frauen im Stresserleben, bei den fatalistisch-externalen Kontrollüberzeugungen, bei der Stressanfälligkeit, der Depressivität und bei körperlichen Beschwerden, sowie ihre geringeren Werte im Selbstwertgefühl und im Selbstkonzept eigener Fähigkeiten auf den Geschlechtsunterschied in der Besorgnisneigung zurückführen. Messungen der Cortisol-Aufwachreaktion und des Cortisol-Tagesprofils sind von der Neigung zur Besorgnis unabhängig. Die Befunde werden zur Erklärung der geschlechtsabhängigen Diskrepanz zwischen Morbidität und Mortalität herangezogen.

Blindsight after optic nerve injury indicates functionality of spared fibers

Some patients with lesions in the geniculostriate pathway (GSP) can respond to visual stimuli in the blind field without conscious acknowledgement. The substrate for this "blindsight" is controversial: whether it is the uninjured extrastriate pathway (EXP), which bypasses the lesion site, or residual fibers within damaged visual cortex ("islands of vision"). Using stimulus detection, localization, and spatial summation tasks, we have found blindsight in patients with damage both in the optic nerve (ON) and EXP. The prevalence and functional characteristics of their blindsight are indistinguishable from that in patients with GSP lesions, so blindsight does not require a completely intact EXP. The present findings support the view that a few surviving ON axons within an area of primary damage are sufficient to mediate blindsight: Several combinations of partially intact pathways can transmit information to the extrastriate cortex and the sum of activation of all visual fibers surviving the injury determines if and to what extent blindsight occurs.

Genetic factors, perceived chronic stress, and the free cortisol response to awakening

Recent studies have demonstrated that the free cortisol response to awakening can serve as a useful index of hypothalamus-pituitary-adrenal axis (HPA) activity. This endocrine marker is rather consistent, shows good intraindividual stability across time and appears to be able to uncover subtle changes in HPA regulation. The present twin study investigated genetic factors as sources of the interindividual variation of the cortisol awakening response. Furthermore, the relationship between psychological variables and morning cortisol levels was studied. On two consecutive days saliva samples were collected 0, 30, 45 and 60 minutes after awakening in 52 monozygotic and 52 dizygotic twin pairs. Moreover, samples were obtained at 0800, 1100, 1500 and 2000 h. ('short day-time profile'). Additionally, the participants filled out questionnaires assessing chronic stress load, self-esteem and self-efficacy.Heritability estimates of h(2)=0.40 for the mean increase and of h(2)=0.48 for the area under the response curve indicate a significant impact of genetic factors on cortisol levels after awakening. However, no genetic influence on the short day-time profile could be observed. Furthermore, several aspects of perceived chronic stress, namely 'worries', 'social stress' and 'lack of social recognition' were significantly associated with the awakening cortisol response. The evidence for a medium-sized, yet distinct genetic influence on cortisol levels after awakening is discussed with regard to a potential clinical relevance of genetic determinants of HPA (re)activity. In line with several recent studies, the present findings further support the view that the cortisol awakening responses is consistently enhanced under chronic stress conditions.

Computer-based training for the treatment of partial blindness

Partial blindness after brain injury has been considered non-treatable. To evaluate whether patients with visual-field defects can profit from computer-based visual restitution training (VRT), two independent clinical trials were conducted using patients with optic nerve (n = 19) or post-chiasmatic brain injury (n = 19). In post-chiasma patients, VRT led to a significant improvement (29.4%) over baseline in the ability to detect visual stimuli; in optic nerve patients, the effects were even more pronounced (73.6% improvement). Visual-field enlargements were confirmed by the observation of a visual-field expansion of 4.9 degrees-5.8 degrees of visual angle and improved acuity in optic nerve patients. Ninety five percent of the VRT-treated patients showed improvements, 72.2% confirmed visual improvements subjectively. Patients receiving a placebo training did not show comparable improvements. In conclusion, VRT with a computer program improves vision in patients with visual-field defects and offers a new, cost-effective therapy for partial blindness.

Determination of atrazine in rainfall and surface water by enzyme immunoassay

Rainwater and surface water from four sites in Germany (Bavaria and Lower Saxony) were analyzed for atrazine by enzyme immunoassay from June 1990 until October 1992. The limit of quantification of the immunoassay was 0.02 μg/L with a middle of the test at 0.2 μg/L. About 60 % of the samples contained measurable amounts of atrazine. Seasonal trends were observed, with the highest concentration in the summer months of up to 4 μg/L for rainwater and up to 15 μg/L for surface waters. The highest concentrations were found in agricultural areas, while in the investigated national parks up to 0.56 μg/L could be detected in rain water. This points to long-range atmospheric transport from agricultural areas to pristine national parks. Samples from forest stands usually showed higher atrazine concentrations than samples from open fields. Deposition rates of 10 - 50 μg/m(2) · yr were observed in the national parks and 10-180 μg/m(2) · yr at the agricultural sites. Comparison of results obtained by enzyme immunoassay and GC/MS showed a good correlation of r = 0.95.

Heritability of cortisol responses to human corticotropin-releasing hormone, ergometry, and psychological stress in humans

The present study investigated cortisol responses to three different stimulation procedures, with a focus on the contribution of genetic factors. Thirteen monozygotic (MZ) twin pairs and 11 dizygotic (DZ) twin pairs performed bicycle ergometry until exhaustion and were exposed to the psychological stress of public speaking and mental arithmetic in front of an audience. Furthermore, 9 MZ pairs and 10 DZ pairs were injected with 100 micrograms synthetic human CRH (hCRH). The adrenocortical response to these challenges was monitored by determination of cortisol in saliva. Significant intraindividual stability of baseline cortisol levels was found in females, but was less in males. Maximum cortisol responses to all three stimulation procedures were significantly intercorrelated in males, but in females only the cortisol responses to hCRH and ergometer exercise showed a significant correlation. While a decided influence of genetic factors was observed for all three baseline cortisol levels as well as for the response to hCRH, heredity appeared to be play a minor role in the adrenocortical response to psychological stress. Cortisol changes after bicycle ergometry revealed no impact of genetic factors on the secretion of cortisol in response to strenuous physical exercise.

Consistent sex differences in cortisol responses to psychological stress

In four independent studies, sex differences in cortisol responses to psychological stress were investigated in healthy adolescents and adults (total n = 153). Public speaking and mental arithmetic in front of an audience (Studies 1-3) reliably induced increases in free cortisol levels in both sexes with 2- to 4-fold increases above baseline levels. Mean cortisol responses were 1.5- to 2-fold higher in men compared with women. In Study 3, cortisol profiles were additionally investigated after human corticotropin-releasing hormone (h-CRH) and bicycle ergometry until exhaustion. Here, both sexes showed very similar adrenocortical responses. Furthermore, men showed elevated cortisol levels in anticipation of the psychological stress situation without actually having to perform the tasks (Study 4). Under this condition cortisol concentration was unchanged or decreased in women. From these data we conclude that the observed sex difference does not reflect an overall lower responsiveness of the female adrenal cortex. Although these studies do not provide conclusive data, we suggest sex differences in cognitive and/or emotional responses to distressing psychosocial situations which in turn may influence cortisol secretion.

'Normal' cigarette smoking increases free cortisol in habitual smokers

In habitual smokers salivary cortisol responses to cigarette smoking were investigated. In the first study, 31 adults assigned to two experimental groups smoked either one or two cigarettes of their preferred brand. Mean salivary cortisol levels were significantly elevated after smoking of two cigarettes. In the second study, 10 smokers and 10 nonsmokers provided saliva samples at 20 min intervals over a 12-hr period. While environmental stimuli were paralleled in both groups overall cortisol output was significantly elevated in the smokers. These data suggest that 'normal' cigarette smoking can increase free cortisol levels.