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G Ital Med Lav Erg 2006; 28:1, Suppl Psicologia 1, 34-42 www.gimle.fsm.


PI-ME, Pavia 2006

B.M. Kudielka, S. Bellingrath, D.H. Hellhammer

Cortisol in burnout and vital exhaustion: an overview

Department of Theoretical and Clinical Psychobiology, University of Trier, Johanniterufer 15, D-54290 Trier, Germany

ABSTRACT. In this overview, we summarize findings on hypothalamus-pituitary-adrenal (HPA) axis functioning in burned out and (vitally) exhausted though otherwise healthy subjects as well as clinically diagnosed patients. The main focus will be on basal diurnal free cortisol regulation and cortisol responses to acute psychological stress. First, we describe normal HPA axis regulation as well as dysfunction which manifests in hyper- or hypoactivity. We also briefly illustrate three established methods to assess HPA axis activity, reactivity, and feedback functioning, namely the cortisol awakening rise (CAR), Trier Social Stress Test (TSST), and low-dose Dexamethasone Suppression Test (DST). Then, an up-to-date summary of empirical findings on the relationship between burnout, respectively vital exhaustion, and cortisol is provided including field as well as laboratory studies. Finally, we briefly discuss possible methodologically confounders and speculate on underlying mechanisms explaining, at least in part, how burnout and vital exhaustion might relate to disease vulnerability. Key words: cortisol, burnout, vital exhaustion, HPA axis, saliva, stress.

1. Normal and dysfunctional hypothalamus-pituitary-adrenal axis regulation The hypothalamus-pituitary-adrenal (HPA) axis is a central control and regulatory system of the organism connecting the brain with the endocrine system. This stressresponsive neuroendocrine system helps the organism to adapt to increased demands and to maintain homeostasis after challenge but is also vital for supporting normal physiological functioning. The end-product, cortisol, has a wide range of physiological effects since virtually all of the bodys single nucleated cells are potential targets for cortisol. Cortisol plays a critical role in metabolism by mobilizing resources to provide energy. This helps to overcome the increased metabolic demand presented by a host of challenges. It also regulates or impacts on other important physiological systems, like the immune system, the sympathetic-adrenal-medullary (SAM) axis, the

RIASSUNTO. In questo lavoro riassumiamo i risultati sul burnout e sullesaurimento (vitale) rispetto alla funzione dellasse ipotalamo-ipofisario (HPA), sia in soggetti sani, sia in pazienti con diagnosi accertata. Il principale obiettivo sar quello di esaminare la regolazione del cortisolo libero diurno e le sue risposte allo stress psicologico acuto. Allinizio, descriveremo sia la funzionalit dellasse normale HPA come pure la disfunzionalit che si pu manifestare in situazioni di iper o ipoattivit. Illustreremo anche brevemente tre metodi consolidati per valutare lattivit dellasse HPA, la sua reattivit e la sua modalit di risposta, ossia linnalzamento del cortisolo al risveglio (CAR), il Trier Social Stress Test (TSST) e il Test di soppressione a bassi dosaggi di Dexamethasone (DST). La trattazione include un aggiornamento dei risultati empirici riguardanti la relazione tra il burnout e il rispettivamente tra esaurimento vitale e cortisolo, riferendo sia a studi sul campo sia di laboratorio. Alla fine del lavoro, verranno brevemente considerate le possibili confusioni metodologiche e le spiegazioni dei meccanismi soggiacenti; mentre, nellultima parte, tratteremo come il burnout e lesaurimento vitale potrebbero essere connessi alla vulnerabilit della malattia. Parole chiave: cortisolo, burnout, esaurimento vitale, asse ipotalamo-ipofisario, saliva, stress.

Abbreviations: ACS = Acute Coronary Syndrome ACTH = adrenocorticotropic hormone BO = burnout CAD = Coronary Artery Disease CAR = Cortisol Awakening Rise CFS = Chronic Fatigue Syndrome CRH = corticotropin-releasing hormone DSM-IV = Diagnostic and Statistical Manual of Mental Disorders DST = Dexamethasone Suppression Test HADS = Hospital Anxiety and Depression Scale HPA axis = hypothalamus-pituitary-adrenal axis ICD-10 = International Classification of Diseases IRS = Insulin Resistance Syndrome MBI = Maslach Burnout Inventory ns = non-significant OGTT = Oral Glucose Tolerance Test SAM = sympathetic-adrenal-medullary SCN = suprachiasmatic nucleus sign. = significant SMBQ = Shirom-Melamed Burnout Questionnaire TBS = Teacher Burnout Scale TSST = Trier Social Stress Test VE = vital exhaustion vs. = versus



cardiovascular system, as well as affective and cognitive processes. Under stress, the hypothalamus secretes corticotropinreleasing hormone (CRH). This provokes the release of adrenocorticotropic hormone (ACTH) from the pituitary. Other ACTH secretagogues, like vasopressin, oxytocin, adrenaline and noradrenaline predominantly intensify the effects of CRH. ACTH triggers the secretion of glucocorticoids from the adrenal cortex. In humans the main glucocorticoid is cortisol. Cortisol is predominantly (90-95%) bound to binding proteins in the blood and only 5-10% of the total plasma cortisol circulates as biologically active, unbound, free cortisol. Overall functioning is controlled by several negative feedback loops (for an overview see 1, 4). A dysfunctional HPA axis is associated with manifestations of psychosomatic and psychiatric disorders (for reviews see 1, 4-10). For example, HPA hyperactivity is often found in major depression (11-14) and also seems to be associated with susceptibility to infectious diseases (15) and cardiovascular problems (16, 17). Hypoactivity of the HPA axis system is associated with autoimmune processes such as lupus erythematosis (18, 7), multiple sclerosis (19), neurodermatitis (20, 21) or fibromyalgia, chronic fatigue syndrome, and rheumatoid arthritis (see 4, 9, 10). It is generally accepted that exposure to stress can cause and/or intensify numerous diseases. It has been suggested that enhanced HPA axis functioning might serve as one indicator of allostatic load, an index of cumulative toll on the body. A high allostatic load might result from chronic overactivation or inadequate responses of the stress system (17, 22), and result in a number of negative health outcomes in the long run, such as diabetes, hypertension, cancer, and cardiovascular disease (16, 17). Another version of this overview can also be found in (23).

located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and the alternation of wakefulness and sleep (24). In particular, the cortisol awakening rise (CAR) is a discrete and distinctive part of the cortisol circadian cycle. In healthy adults, salivary free cortisol concentrations increase by 50 to 160% within the first 30 minutes after awakening (27-29). In several recent studies it could be demonstrated that the CAR reflects subtle changes in HPA axis activity and can serve as a useful index of adrenocortical activity (30-32). Furthermore, the CAR can be easily assessed by four saliva samples gained with strict reference to awakening (e.g., +0, +30, +45, +60 minutes after awakening) under a wide variety of clinical and field settings, since it is non-invasive, inexpensive and easy-to-employ (for a review see 33). 2.2 HPA axis reactivity More than ten years ago, the Trier Social Stress Test (TSST) was introduced as a standardized protocol for the induction of moderate psychosocial stress in laboratory settings (34). In a recent comprehensive meta-analysis of 208 laboratory stress studies the TSST turned out to be one of the few available stress protocols which satisfies the criteria of a motivated performance task that combines elements of uncontrollability and high levels of socialevaluative threat (35). The TSST protocol mainly consists of a brief preparation period (3 min) and a test period in which the subject has to deliver a free speech (5 min; job interview) and perform mental arithmetic (5 min) in front of a trained audience (for more detailed up-to-date descriptions see 36 and 37). Until today, this stress protocol has been applied in more than 4,000 subjects all over the world including younger and older adults, children as well as clinical populations. 2.3 HPA axis feedback sensitivity The Dexamethasone Suppression Test (DST) is routinely used for the assessment of HPA axis feedback sensitivity. The synthetic glucocorticoid dexamethasone acts primarily at the level of the pituitary and mimics the negative feedback effects of endogenous cortisol on ACTH and the subsequent cortisol release via binding to the glucocorticoid receptor (38-40). Pre-medication with dexamethasone normally takes place the night before cortisol samples are collected (e.g., 23 PM). Application of a low dose of dexamethasone with concentrations of 0.5 mg or even 0.25 mg in humans (so-called low-dose DSTs) is preferable in order to not completely suppress endogenous cortisol levels measured at the following day, for example allowing for hypersuppression (strong suppression) or indications of non-suppression (less suppression) (41, 42). In sum, the DST is a test of HPA axis negative feedback efficiency, indicated by the amount of cortisol suppression after oral dexamethasone intake.

2. Assessment of HPA axis activity, reactivity, and feedback functioning To characterize different facets of HPA axis functioning, various methods have been applied focusing for example on HPA axis diurnal activity, reactivity to acute stress as well as the systems feedback sensitivity. For instance, it is conceivable that homeostatic control might be maintained under basal conditions while the impact of chronic stress is more prominent or might emerge primarily under stimulated conditions. Therefore, three established and widely-used research tools for the assessment of HPA axis regulation are briefly presented in the following. 2.1 HPA axis activity The adrenal hormone cortisol shows a pronounced circadian rhythm with typically lowest secretion during the first half of night time sleep (quiescent period), an abrupt elevation during the second half of sleep, peak levels shortly after morning awakening and continuously decreasing levels over the remainder of the day, except for stress-related cortisol surges that superimpose on the normal circadian rhythm (24-26). The two major processes controlling the overall diurnal cortisol variation are the circadian signal generated by the circadian pacemaker

3. Burnout and vital exhaustion: definitions Burnout (BO) is a non-psychiatric syndrome mostly defined by the three core dimensions 1. emotional



exhaustion, 2. a cynical work attitude, and 3. feelings of work inefficacy and is thought to be a prolonged response to chronic emotional and interpersonal stress probably accompanied by insufficient recovery (43). Others identified burnout as a work-related construct uniquely characterized by the chronic depletion of an individuals intrinsic energetic or coping resources (44). Burned out individuals may experience additional physical symptoms (e.g., nonspecific pain, recurrent headaches, gastro-intestinal problems) and disturbed sleep or suffer from attentional difficulties which manifest subjectively as well as objectively (45). BO has often been described in individuals with a high sense of job ideals and whose jobs require a high degree of social interactions (so-called people-oriented professionals) such as teachers, caregivers, nurses, doctors, social workers, firefighters, policemen, etc. (43, 46, 47). BO is mostly measured using the Maslach Burnout Inventory (MBI) encompassing the three subscales Emotional Exhaustion, Depersonalization, and Lack of Accomplishment (48). Others applied the ShiromMelamed Burnout Questionnaire (SMBQ) comprised of up to four subscales (emotional exhaustion and physical fatigue, tension, listlessness, and cognitive weariness; 49, 50) or less frequent the Teacher Burnout Scale (TBS) based on the four scales Career Satisfaction, Perceived Administrative Support, Coping with Job-related Stress, and Attitude towards Students (51). For further more detailed discussion of the conceptual basis of BO and other measures of burnout not included in this review see Shirom and coworkers (46, 52). Although research on the relationship between burnout or vital exhaustion and health is relatively new, accumulated evidence suggests that BO acts as a risk factor for mental and physical ill health via different pathways (for reviews see 47, 53). A psychological state that is also viewed as a potential consequence of long-term, chronic stress, or a chronic state of burnout is vital exhaustion (VE). VE is characterized by 1. unusual fatigue, 2. loss of mental and physical energy, 3. increased irritability, and 4. a feeling of demoralization and is measured by the Maastricht Vital Exhaustion Questionnaire (MVEQ; 54, 55). Interestingly, in several epidemiological studies, VE has been established as an independent risk factor for coronary artery disease (CAD; 56-58) (for reviews see also 59, 60). A recent outline of the history of the concept of vital exhaustion can be found in Appels (61). Based on these definitions, it is obvious that burnout and vital exhaustion share conceptual similarities. Consequently, a high correlation was for example reported between burnout and vital exhaustion (r=.68, p=.001, N=56, measurements: SMBQ and MVEQ; 62) and subjects scoring high and low on burnout also differed significantly on VE (63). Appels & Schouten (64) hypothesized that the state of vital exhaustion before a myocardial infarction may be a reactivation of an earlier period of burnout. In addition, symptoms of burnout and vital exhaustion appear to overlap with such conditions as the chronic fatigue syndrome (CFS) or fibromyalgia and correlate moderately with depression and anxiety (47, 53, 61, 65, 66). However, we could recently show in a factor analysis based on a

sample of N=822 workers that vital exhaustion (MVEQ) constitutes a distinct psychological concept compared to depressive symptomatology as measured by the depression subscale of the Hospital Anxiety and Depression Scale (HADS) and negative affectivity as measured by the respective subscale of the Type-D Questionnaire (67).

4. HPA axis regulation in burnout and vital exhaustion: empirical findings To-date, there is still a paucity of data on HPA axis regulation in burnout and even less is known about HPA axis functioning in vital exhaustion. Furthermore, published studies seem to render contradictory results. In the following, we summarize the existing literature on cortisol regulation under (a) basal and (b) acute stress conditions in burned out and (vitally) exhausted subjects. The main focus will be on psychological stress, but studies using pharmacological stimulation procedures are also shortly presented. It has to be considered that different pharmacological stimulation tests act at different levels of the HPA axis involving different feedback loops at different levels in the system which complicates the comparability of different study designs and interpretation of results. In each section, we will first report on data based on burned out or exhausted but otherwise healthy subjects (without any clinical diagnosis) and then summarize evidence including patients with a clinical diagnosis, if available. As recently outlined by Shirom (53) there are still no clinically validated cut-off points available with respect to any of the above-described psychometric instruments used to assess burnout. The presently reviewed studies mostly based their clinical diagnoses of burnout on the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) and ICD-10 (International Classification of Disease and Related Problems) and include patients who meet the criteria for adjustment disorder (DSM-IV 309.xx; ICD-10 F43.xx) (see 68), work-related neurasthenia (ICD-10 F48.xx) or undifferentiated somatoform disorder (DSM-IV 300.81) (see 69, 70). Others based their clinical diagnosis on semistructured diagnostic interviews conducted by a clinical psychologist (see 71 and 72). 4.1 HPA axis activity 4.1.1 Burnout (BO) As indicated, we first resume studies based on nonclinical subjects. Examining total cortisol levels in a single blood sample, two studies by Grossi and coworkers (63, 73) applying the SMBQ and an unpublished dissertation by Sderfeldt (74) could not reveal associations between cortisol and burnout (measured by the emotional exhaustion subscale of the MBI). These insignificant results can presumably be attributed to the chosen blood sampling designs (single venipunctures). Contrary, the unpublished diploma thesis of J. Hellhammer (75) raised the idea of low 8 AM levels of salivary cortisol in nurses suffering from burnout accompanied by multiple bodily complaints. Based on these preliminary findings, school teachers scoring high



(N=30) and low (N=36) on two burnout questionnaires (MBI and TBS) were requested to collect four cortisol samples in the first hour after awakening on three consecutive days (sampling here: +0, +15, +45, +60 minutes after awakening). The third testing included a low-dose (0.5 mg) DST (76). According to J. Hellhammers initial finding, subjects high on burnout showed a lower cortisol awakening rise (CAR) at day 1 and 2 as well as a greater suppression of the free cortisol secretion after dexamethasone premedication the night before sampling. Also, in a sample of 41 US soldiers, Morgan et al. (77) observed that higher levels of burnout were related to lower cortisol levels in the morning, but higher cortisol concentrations in the evening, which might be indicative of a reduced diurnal variation of cortisol or a flattened diurnal secretory cycle in burned out military personnel. In contrast, Melamed and coworkers (78) observed higher salivary cortisol levels in the morning and afternoon in industrial workers with non-chronic (N=22) and chronic burnout (N=37) compared to employees without burnout symptomatology (N=52). However, in the two latter studies only two samples per subject were gained at fixed time points. Finally, Ekstedt and coworkers (79) did not observe differences in a single morning plasma cortisol level, a cortisol awakening profile nor the diurnal cortisol cycle (measured by nine saliva samples) in a relatively small sample of 24 employees of a computer company scoring high versus low on the SMBQ (personal communication). Finally, a few studies can be cited that investigated basal HPA axis functioning in clinically diagnosed burnout patients compared to healthy controls or subjects with low or medium burnout scores. Over a four month period, Moch et al. (72) measured the free cortisol secretion in 24/h urine samples before and after a stress management program in 16 female burnout patients (measurements once a month) and a healthy untreated control group (measurements at first and fourth month). Compared to controls, patients showed a reduced cortisol excretion regardless of clinical and psychological improvement due to the intervention. Also, 8 AM cortisol serum concentrations (but not ACTH levels) were significantly lower in patients than controls at month four. In a pilot study, Mommersteeg et al. (69) found lower salivary cortisol levels after awakening in clinically diagnosed burnout patients (N=22) who were either on partial or full sick-leave compared to a healthy control group (N=21). However, the groups did not differ in cortisol levels during the remainder of the day. Fourteen sessions of psychotherapeutic intervention led to a significant increase of the initially lowered morning cortisol levels, but there were no significant correlations between changes in CAR and improvements of psychological complaints. Contrary, De Vente and colleagues (71) observed higher cortisol levels after awakening in a group of 22 clinically diagnosed burnout patients compared to 23 healthy controls, and no differences at 12 AM. Very recently, Grossi and coworkers (68) recruited 22 subjects scoring low on burnout (LB), 20 subjects scoring moderate on burnout (MB) as well as 22 burnout patients scoring high on burnout (HB). Sexspecific ANOVA analysis of morning cortisol profiles

revealed that there was no significant main effect of group in men while female patients (HB: N=13) had a significantly higher CAR than subjects with low burnout (LB: N=13), while cortisol curves of subjects with moderate burnout fall in between (MB: N=9). Finally, in a highly controlled study by Mommersteeg and colleagues (70) comprising 74 clinically diagnosed burnout patients and 35 healthy controls, clinical burnout was not reflected in the CAR, the diurnal cortisol day curve (12 AM, 6 PM, 10:30 PM) nor the low-dose (0.5 mg) DST (each covered by three saliva samples). 4.1.2 Vital exhaustion (VE) Much less evidence can be found on vital exhaustion. In 34 healthy white collar workers, Dahlgren et al. (80) collected five salivary cortisol samples during one day of each a work week with high as well as low stress. While one group of subjects showed higher morning cortisol levels in the high stress week compared to the low stress week, the other group showed an opposite pattern. The latter group was characterized by higher workload, fatigue, and exhaustion during both weeks. Based on an initial questionnaire screening of 577 male volunteers, 54 potential VE cases and 33 control subjects were selected for the Maastricht Interview for Vital Exhaustion, a structured interview designed to evaluate frequency, severity, and duration of VE symptoms. In a final sample of 29 VE and 30 controls, Nicolson & van Diest (81) observed a pattern of marginally lower basal salivary cortisol levels throughout a day (covered by five saliva samples) with significantly lower cortisol concentrations in the evening (two samples) in exhausted subjects versus healthy controls. In contrast, in a large sample of N=238 female patients with acute coronary syndrome, Koertge et al. (58) found a small but significant positive association between vital exhaustion and total cortisol measured by a single morning blood sample (r=.13, p.05). 4.2 HPA axis reactivity 4.2.1 Burnout In addition to the assessment of basal HPA axis activity, De Vente and colleagues (71) also applied a laboratory stress protocol. Although significant differences in cortisol levels over the course of the test session are reported between burnout patients and controls, a closer inspection of stress responses revealed that the chosen task (speech, mental arithmetic) did not elicit a task-related cortisol response and observed group differences were based on higher pre-stress (baseline) cortisol levels in burnout patients. 4.2.2 Vital exhaustion Kristenson and coworkers compared Lithuanian versus Swedish men in a cross-cultural comparison and found that low peak cortisol responses to a standardized laboratory stress battery (anger recall, mental arithmetic, cold pressure test) were significantly related to high baseline cortisol levels and vital exhaustion (82-84). Also, the data from Nicolson & van Diest (81) support the idea of a subtle hyporeactivity in participants with high vital exhaustion. Although controls and thoroughly selected vitally



exhausted subjects showed statistically comparable overall cortisol responses to a laboratory speech task, exhausted subjects were less likely to show a significant response (six responders in 30 controls and no responder in 28 VE subjects). However, provoked cortisol increases were extremely small with mean increases of 1.36 nmol/l in controls and 0.79 nmol/l in VE. Recently, we applied the TSST three times in 25 healthy middle-aged male employees with test sessions one week apart (85). Focusing in a first step on the first stress session, the study results show that VE may rather be associated with reduced cortisol responses to acute stress, although the respective analysis was not significant (p=.14). Accounting for the repeated stress procedure, data revealed that mean cortisol responses showed the well-known general habituation effect across test exposures. Interestingly, mean cortisol responses varied across stress sessions depending on the extent of exhaustion. Linear regression revealed a negative dose-response relationship between exhaustion and the degree of habituation. We identified 19 individuals showing a response habituation (negative slope) and six individuals showing a response sensitization over the three sessions (positive slope) with the latter reporting higher exhaustion scores. We assume that situational or psychological factors initially mask an existing impact of exhaustion since in this study effects of exhaustion became fully apparent only after repeated stress exposure. In a research project based on 69 normotensive and 21 borderline hypertensive men, Keltikangas-Jrvinen and coworkers investigated the hypothesis that various psychological and behavioral characteristics (including vital exhaustion, depression, type A behavior, hostility, and anger) might be associated with the insulin resistance syndrome (IRS) as indicated by neuroendocrine responses to pharmacological stimulation (86-90). Their results showed that vital exhaustion combined with depression was negatively correlated with mean ACTH levels and positively correlated with the mean cortisol/ACTH ratio during oral glucose tolerance testing. Furthermore, the net increase of cortisol after intravenous ACTH stimulation with DEX-premedication differed significantly between subjects scoring high versus low on exhaustion with higher cortisol increases in the highly exhausted group.

5. Possible confounders and mechanisms The above cited literature shows that the evidence on possible relationships between burnout and vital exhaustion on the one hand and HPA axis (dys)regulation on the other remain somewhat inconsistent. For example, there are studies showing either lower, higher or unchanged cortisol awakening profiles in groups with higher levels of burnout. It can only be speculated why the picture of results is relatively inconsistent. Inconstancies between studies can probably be, at least in part, ascribed to methodological aspects as well as confounding or intervening factors of HPA axis regulation. First of all, the cited studies used different psychometric scales to measure burnout or used different clinical diagnosis criteria for the

inclusion of patient groups. Furthermore, different HPA axis outcome parameters were measured (ACTH, total cortisol in blood, salivary free cortisol) and different sampling procedures have been applied (single venipuncture, CAR, etc.). Only some studies controlled for psychological factors that might have influenced selfreport, like negative affectivity, depression, or anxiety. Furthermore, burnout and vital exhaustion may differentially be related to HPA axis regulation in men and women, as indicated by Grossi et al. (68). In most of the past studies, data was only available in men or women, while others collected data in both men and women, but subsequently combined the groups to form one sample. Consequently, there is still a paucity of data on the potential modifying role of gender. Future studies should be aware of such possible gender-specific effects. It is also conceivable that other subgroups exist which remain to be defined in the future (for example, age or years of employment might be further important factors). Likewise important, other factors are known to impact significantly on basal or stress-related cortisol concentrations, like medication intake, time of awakening (for assessment of CAR), subjects compliance (for ambulant saliva sampling), the female menstrual cycle phase or intake of oral contraceptives (for HPA axis outcomes under stress), smoking habits, kind of applied stress protocol, etc. (28, 30, 91; for reviews see 33, 36, 37). While several examples could be generated, we just want to outline a few: If time of awakening is not standardized or controlled while assessing morning cortisol levels, it is not unlikely that absolute cortisol levels as well as morning increases differ between high versus low burnout subjects or hospitalized patients just because of different awakening times (29, 92, 93). It is also conceivable that subjects compliance with an ambulant saliva sampling procedure is significantly associated with the level of chronic stress. So, if chronically stressed subjects are systematically less or more adherent than controls, different cortisol profiles will be observed between groups of interest (94-96). In respect to HPA axis stress responses, total and free cortisol responses are significantly dependent on the female menstrual cycle phase and intake of oral contraceptives (97). Besides these important methodological issues, we would like to speculate on possible underlying mechanisms. Based on their null-findings in a highly controlled and very wellconducted study, Mommersteeg et al. (70) speculated whether HPA axis dysregulation might be apparent during the development of burnout but wane in the period after the diagnosis of burnout. This hypothesis remains to be tested empirically. In respect to possible other mechanisms it might be hypothesized if chronic stress may first lead to hyperactive functioning, while the system turns to hypoactive functioning when a state of exhaustion is reached and the individual is no longer able to cope with environmental stress. This reasoning would be in line with several other empirical reports on increased basal free cortisol levels in the morning in chronically stressed individuals due to work overload, social stress and lack of social recognition, or chronic unemployment (30, 98-100). Additionally, in the above outlined study on burnout by Pruessner and coworkers (76), perceived stress correlated with increased cortisol levels



Table I. Summary of empirical studies on HPA axis regulation in (A) burnout and (B) vital exhaustion
(A) Burnout Subjects high versus low on BO (without clinical burnout diagnosis) Grossi et al., 1999 Grossi et al., 2003 single blood sample between 8-10 AM: total cortisol single blood sample between 8-10 AM: total cortisol no association BO and cortisol no group differences high versus low BO ns ns ns ns ns ns ns

Pruessner et al., 1999 CAR (4 samples) on 3 consecutive days: salivary cortisol lower CAR in high BO low-dose DST (0.5 mg DEX) and CAR (4 samples): after DEX lower CAR in high BO salivary cortisol Morgan et al., 2002 morning and evening samples: salivary cortisol (exact time points not given, p/F statistics not given) [total cortisol] 8 AM and 4 PM salivary cortisol single blood sample between 8-9 AM: total cortisol CAR (4 samples): salivary cortisol diurnal cortisol cycle (5 samples): salivary cortisol 24/h cortisol in urine (before and after intervention) single blood sample 8 AM: total cortisol single blood sample 8 AM: ACTH lower morning levels in high BO higher evening levels in high BO [results not reported] higher 8 AM levels in BO higher 4 PM levels in BO no group differences high versus low BO no group differences high versus low BO no group differences high versus low BO lower levels in BO patients lower 8 AM levels in BO patients at month 4 no group differences

Melamed et al., 1999 Ekstedt et al., 2004

Clinically diagnosed burnout patients versus controls Moch et al., 2003

Mommersteeg et al., in press

CAR (3 samples): salivary cortisol lower CAR in BO patients diurnal cortisol cycle (3 samples): salivary cortisol no group differences (patients vs. controls) CAR (3 samples): salivary cortisol after psychotherapy increased CAR in BO patients after psychotherapeutic intervention CAR (3 samples): salivary cortisol 12 AM: salivary cortisol laboratory stress test (speech, mental arithmetic): salivary cortisol CAR (4 samples): salivary cortisol CAR (3 samples): salivary cortisol diurnal cortisol cycle (3 samples): salivary cortisol low-dose DST (0.5 mg DEX) and CAR (3 samples): salivary cortisol diurnal cortisol cycle (5 samples: +15 min after awakening, 10 AM, 1 PM, 4 PM, bedtime) once during each a week with high and low stress levels: salivary cortisol day 1 - evening samples (9:30 PM, 10:35 PM): salivary cortisol day 2 - diurnal cortisol cycle (6:55 AM, 11 AM, 4 PM, 5:40 PM, 7 PM): salivary cortisol laboratory speech task single blood sample between 8-9 AM: total cortisol standardized laboratory stress battery (anger recall, mental arithmetic, cold pressure test): total cortisol and salivary cortisol (cross-cultural comparison of Lithuanian versus Swedish men) 3 TSST exposures one week apart: salivary cortisol

De Vente et al., 2003

higher CAR in BO patients no group differences ns no task-related response (sign. group differences attributable to higher pre-stress (baseline) levels in BO patients higher CAR in female BO patients no group differences in men no group differences (patients vs. controls) no group differences (patients vs. controls) no group differences (patients vs. controls) (females) ns (men) ns ns ns

Grossi et al., 2005 Mommersteeg et al., 2006

(B) Vital Exhaustion Dahlgren et al., 2004 group with low morning cortisol levels in high stress week compared to the low stress week had higher workload, fatigue, and exhaustion lower levels in VE patients marginally lower levels in VE patients (p=.08) significant response less likely in VE patients small positive association between VE and cortisol in females with ACS (r=.13, p.05)

Nicolson & van Diest, 2000


Koertge et al., 2002 Kristenson et al., 1998, 2001, 2005

baseline saliva cortisol marginally positively () associated with VE (r=.13, p=.09) peak saliva (r=-.16, p=.04) and total cortisol (r=-.22, p=.003) negatively associated with VE VE associated with reduced habituation across 3 stress exposures in males VE marginally associated with lower cortisol responses to first stress exposure (p=.14) VE + depression negatively correlated with mean ACTH, positively correlated with mean cortisol/ACTH ratio (normotensive and hypertensive men) higher cortisol net increases in high VE group ()

Kudielka et al., 2006

Keltikangas-Jrvinen OGTT: ACTH and total cortisol et al., 1996a, 1996b, 1997, 1998 Rikknen et al., 1996 DST (1 mg DEX) - ACTH stimulation: total cortisol



during the first hour after awakening. As indicated in the Table, studies on vital exhaustion, by the majority, point to a hypoactive HPA axis while studies on burnout are much more controversial. However, for stress reactivity conclusions are more difficult, since some stress protocols applied in chronically stressed individuals did not evoke significant cortisol increases (101, 102) and others did not observe different cortisol responses in groups with and without chronic life stress (103). However, the latter observation fits to our finding, showing that the impact of VE appears not until repeated stress exposures (85). Impaired habituation to repeated stress might be one potential pathway (beside others) how exhaustion relates to increased disease vulnerability over time. While in the allostatic load model (see above) lack of habituation is conceptualized as a high initial stress response and a lack of habituation to subsequent (comparable) stress exposures, our data (85) suggest that a lack of habituation might also be associated with a weakened initial stress response, indicating a reduced capability of the subjects HPA axis to adapt to repeated stress exposure. This fits also to the findings by Nicolson & van Diest (81) and Kristenson and coworkers (82-84). It might even be speculated that a nonadaptive stress system (here: inability to habituate to stress) might cause the inability to show a normal activation when confronted with a new stressor. Such a pattern could be disadvantageous in two ways: in situations with a high need of energy there is no adequate supply (e.g., in highly demanding, stressful, new situations etc.) while in the long run a lack of adaptation (no response reduction when repeatedly confronted with similar situations) repeatedly leads to system activation. In the long run, both mechanisms could contribute to the wear and tear of the organism. In sum, the now classical statement by Rose (104) that so-called response habituation after repeated stimulation is a key characteristic of HPA axis functioning could be supplemented by the finding that a consequence of chronic stress (exhaustion) might moderate this habituation process. Of course, this observation has first to be confirmed in future studies. Such habituation probably reflects changes over time in multiple situational factors like perceived novelty, uncontrollability, threat, etc. (see 105). Since an insufficient ability to adjust or habituate to repeated exposure to the same stressor is considered as one condition that leads to allostatic load and could reflect a state of increased vulnerability, it may be concluded that absence of normal habituation to repeated stress might be one potential mechanism how exhaustion relates to increased disease vulnerability. Overall, there seems to be a considerable divergence on data regarding HPA axis functioning in chronically distressed individuals. Hyperactivity of the HPA axis (including excess release of cortisol and a consequent suppression of immune-mediated inflammation) has been seen during chronic stress while HPA axis hypoactivity with a decrease of cortisol release and an increased susceptibility to immune-mediated inflammation has been reported in the chronic fatigue syndrome and after chronic stress (6, 9, 106-108). As suggested earlier, hypocortisolism may be the consequence of prolonged stress (or trauma) and there may be a time course in the development of this neuroendocrine abnormality (109). Possible mechanisms how initial HPA

axis hyperactivity may eventually lead to a hypoactive state include dysregulations on several levels of the HPA axis. As outlined in detail by Heim and coworkers (9), the development and persistence of hypocortisolism may be due to reduced biosynthesis or depletion at several levels of HPA axis (CRH, ACTH, cortisol), CRH hypersecretion and adaptive down-regulation of pituitary CRH receptors or change in receptor sensitivity, increased feedback sensitivity of the HPA axis, and morphological changes (109). For further discussion see also Melamed et al. (47). To summarize, chronic stress in terms of burnout and vital exhaustion seems to be associated with dysregulations of basal HPA axis functioning as well as HPA axis responses under stress. However, the observed direction remains still inconsistent and even some very well-conducted studies could not find associations between burnout and HPA axis dysregulations. Therefore, future studies should (a) pay attention to already known intervening and moderating factors of HPA axis regulation and (b) carefully differentiate acutely stressed, chronically stressed, and vitally exhausted, respectively burned out, subgroups. Regarding the HPA axis, one may attempt to differentially discriminate activity and reactivity patterns with respect to specific alterations of extrahypothalamic, hypothalamic, pituitary, adrenal, and receptor functions (endophenotyping).

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