Salivary cortisol is often used in occupational field studies when measuring stress reactions. For purposes of precision and accuracy in measurement, and interpretation of results, it is crucial to know the sources of variability that exert systematic influence on sampling. Variability can be both biological and methodological in origin, and failure to identify its sources may induce erroneous interpretations of Type I and Type II. This review aims to increase our knowledge and provide an overview of the biological and methodological variations of relevance for field measurements of salivary cortisol. It is concluded that: (i) time of sampling has to be carefully registered and included in the statistical analysis; (ii) samples have to be collected at the same time of year in longitudinal designs; (iii) food intake has to be avoided in at least the 2 h before sampling; (iv) vigorous exercise has to be avoided in at least the 2 h, preferably longer, before saliva is collected for measurement of cortisol; (v) variation in results obtained by different laboratory techniques emphasizes use of the same, or otherwise made comparable, laboratory techniques; (vi) concentration of cortisol is dependent on the material of the tampon; (vii) despite the absence of hard evidence, it is recommended that information be collected and results possibly statistically controlled for alcohol consumption, medication, such as oral contraceptives, and treatment for mental diseases; (viii) saliva samples can be stored at -20 degrees C for at least 1 year; (ix) cross-comparisons of absolute concentrations across studies might be difficult and therefore the establishment of reference intervals for the population studied and method used is recommended.

Purpose: The purpose of this paper is to investigate whether and how knowledge hoarding, functions as antecedent and consequent of work related negative acts, as a measure of bullying. The authors investigate the relation as mediated by trust and justice.Design/methodology/approach: Data stem from a longitudinal study in which questionnaire responses were collected twice from 1,650 employees in 52 workplaces. Structural equation modelling was used to analyse the two models. Design-based corrections were made to accommodate the multi-level structure of data.Findings: The analyses showed that knowledge hoarding was both an antecedent and a consequent of negative acts. First, over time, knowledge hoarding was indirectly related to negative acts mediated by trust and justice. Second, negative acts were both directly and indirectly related to knowledge hoarding over time. The study thus points to the existence of a vicious circle of negative acts, psychological states of trust and justice, and knowledge hoarding behaviours, which presumably will affect both individual and organizational outcomes negatively.Research limitations/implications: The use of already collected, self-report data, single-item measures, and the two-year time lag could pose potential limitations to the study.Practical implications: Preventive and repair actions could potentially impact both negative acts and knowledge hoarding by focusing on increasing the social exchange quality at work unit level.Originality/value: This paper combines two strands of research, that of bullying at work and that of knowledge management, within which research on knowledge hoarding has been an under-researched area.

Teachers are at high risk of stress-related disorders. This longitudinal study aimed to (a) identify which occupational, sociodemographic and life-style factors and self-efficacy at baseline that were of importance for burnout, (b) explore associations between changes in the studied factors versus changes in burnout, and (c) by interviews increase the understanding of perceived job demands among teachers. A cohort of 310 Swedish teachers in school-years 4–9 responded to a questionnaire of occupational, sociodemographic and life-style factors, self-efficacy and burnout, at baseline and at follow-up (mean 30 months later). A combined measure with four levels of burnout was crafted, based on exhaustion, cynicism and professional efficacy (Maslach Burnout Inventory-General Survey). Quantitative data were analysed with multiple ordinal regression, and qualitative data were analysed with content analysis of interview responses from a subgroup of the teachers (n = 81). The occurrence of high burnout (level 2 and 3 combined) were similar at baseline and follow-up (14% vs. 15%). However, many teachers fluctuated between the levels of burnout (28% increased and 24% decreased). Burnout at baseline was of importance for change of work or being off duty at follow up. In the multi-exposure model, low self-efficacy [OR 0.42; CI 0.26–0.68] and high job demands [OR 1.97; CI 1.02–3.8] were the strongest explanatory variables. Low self-efficacy remained as the strongest explanatory factor after adjustment for burnout at baseline. Increased job demands during follow-up was associated with an increased level of burnout [OR 3.41; CI 1.73–6.69], whereas increased decision latitude was associated with a decreased level of burnout [OR 0.51; CI 0.30–0.87]. Two major categories of demands emerged in the qualitative analysis; i.e. too high workload and a sense of inadequacy. A substantial proportion of teachers showed signs of burnout at both occasions. Low self-efficacy and high job demands was of importance for burnout, and changes in burnout was further associated with changes in decision latitude. The results points to the need of actions on individual, organizational and a societal levels.

Measurement of cortisol concentration can contribute important information about an individual's ability to adjust to various environmental demands of both physical and psychosocial origin. However, one uncertainty that affects the possibilities of correctly interpreting and designing field studies is the lack of observations of the impact of seasonal changes on cortisol excretion. For this reason, the month‐to‐month changes in diurnal cortisol concentration, the awakening cortisol response (ACR), maximum morning concentration, and fall during the day were studied in a group of 24 healthy men and women 32 to 61 yrs of age engaged in active work. On one workday for 12 consecutive months, participants collected saliva at four time points for determination of cortisol: at awakening, +30 min, +8 h, and at 21:00 h. Data were analyzed by a repeated measures design with month (12 levels) and time‐of‐day (4 levels) as categorical predictors. Cortisol concentrations were analyzed on a log scale. The diurnal pattern of cortisol was similar across months (interaction between month and time of day: p>0.4). The main effects of month and time‐of‐day were statistically significant (p <0.001). Highest concentrations were observed in February, March, and April, and lowest concentrations were observed in July and August. There were no statistically significant effects in any of the other measures, or between men and women. In conclusion, a seasonal variation in salivary cortisol concentrations was detected in an occupationally active population. Thus, seasonal variation needs to be taken into account when designing and evaluating field studies and interventions and when making comparisons across studies.