Regulation of reinforcement learning parameters captures long-term changes in rat behaviour.

In uncertain environments in which resources fluctuate continuously, animals must permanently decide whether to stabilise learning and exploit what they currently believe to be their best option, or instead explore potential alternatives and learn fast from new observations. While such a trade-off has been extensively studied in pretrained animals facing non-stationary decision-making tasks, it is yet unknown how they progressively tune it while learning the task structure during pretraining. Here, we compared the ability of different computational models to account for long-term changes in the behaviour of 24 rats while they learned to choose a rewarded lever in a three-armed bandit task across 24 days of pretraining. We found that the day-by-day evolution of rat performance and win-shift tendency revealed a progressive stabilisation of the way they regulated reinforcement learning parameters. We successfully captured these behavioural adaptations using a meta-learning model in which either the learning rate or the inverse temperature was controlled by the average reward rate.

Does salivary cortisol secretion mediate the association of work-related stressors with workers' depression?

PURPOSE: The purpose of this study was to verify the mediating role salivary cortisol intensity plays between work organization conditions and depression. This study simultaneously considered psychological and physiological (salivary cortisol) stress indicators on workers' depression in a single model. METHODS: We relied on cluster sampling of 341 workers in 34 Quebec establishments. Five saliva samples (on awakening, 30 min after awakening, at 2:00 p.m., 4:00 p.m., and bedtime) were collected per day. The weekly collection period spanned a period of 3 days (1 day off and 2 work days). We evaluated the main effects of work organization conditions on salivary cortisol intensity and depression, as well as the mediation effect of salivary cortisol intensity between work organization conditions and depression. To adjust for design effects, the direct and indirect (mediation) associations between the variables were evaluated while accounting for the non-independence of the data. RESULTS: Skill utilization and job insecurity were associated with salivary cortisol intensity, while psychological demands and job insecurity were associated with higher depression levels. Work-related variables were not found to have an indirect effect on depression via worker's salivary cortisol (AUC) intensity. CONCLUSION: Work-related stressors examined in this study did not indirectly affect worker's depression levels. Additional studies are necessary to be able to identify all work-related stressors that could potentially increase worker's depression levels through salivary cortisol.

Manipulating the revision of reward value during the intertrial interval increases sign tracking and dopamine release.

Recent computational models of sign tracking (ST) and goal tracking (GT) have accounted for observations that dopamine (DA) is not necessary for all forms of learning and have provided a set of predictions to further their validity. Among these, a central prediction is that manipulating the intertrial interval (ITI) during autoshaping should change the relative ST-GT proportion as well as DA phasic responses. Here, we tested these predictions and found that lengthening the ITI increased ST, i.e., behavioral engagement with conditioned stimuli (CS) and cue-induced phasic DA release. Importantly, DA release was also present at the time of reward delivery, even after learning, and DA release was correlated with time spent in the food cup during the ITI. During conditioning with shorter ITIs, GT was prominent (i.e., engagement with food cup), and DA release responded to the CS while being absent at the time of reward delivery after learning. Hence, shorter ITIs restored the classical DA reward prediction error (RPE) pattern. These results validate the computational hypotheses, opening new perspectives on the understanding of individual differences in Pavlovian conditioning and DA signaling.

Chronic diseases, age and gender: examining the contribution to burnout symptoms in a sample of 2075 Canadian workers.

PURPOSE: This cross-sectional study aims to evaluate the role of chronic diseases, and their interactions with age and gender, on the emotional exhaustion component of the burnout syndrome. METHODS: Data came from the Salveo Study conducted in 2009-2012. It contained a random sample of 2075 Canadian workers employed in 63 workplaces. Multilevel regression models were estimated. Main effects of chronic diseases were first evaluated, and then age-chronic diseases interactions were tested. Analyses were performed on the total sample and stratified by gender. All analyses were adjusted for work conditions decision latitude, physical and psychological demands, work hours, social support and rewards. RESULTS: Mental and behavioural disorders, diseases of the nervous system, the musculoskeletal system and connective tissue, and genitourinary system are associated with a higher level of burnout symptoms. Associations with mental and behavioural disorders, and diseases of the nervous system are stronger for men than women. Age increases the association of behavioural disorders, diseases of the nervous system, and genitourinary system and burnout. Age may moderate the association of nervous and genitourinary systems diseases with burnout in women. CONCLUSION: Workplaces must be more proactive to better recognise the role of chronic diseases on burnout and to implement preventive measures. The development of interventions towards specific risk groups is needed.

Developing and maintaining the resilience of interdisciplinary cancer care teams: an interventional study.

BACKGROUND: Providing care to cancer patients is associated with a substantial psychological and emotional load on oncology workers. The purpose of this project is to co-construct, implement and assess multidimensional intervention continuums that contribute to developing the resilience of interdisciplinary cancer care teams and thereby reduce the burden associated with mental health problems. The project is based on resources theories and theories of empowerment. METHODS: The study will involve cancer care teams at four institutions and will use a mixed-model design. It will be organized into three components: (1) Intervention development. Rather than impose a single way of doing things, the project will take a participatory approach involving a variety of mechanisms (workshops, discussion forums, surveys, observations) to develop interventions that take into account the specific contexts of each of the four participating institutions. (2) Intervention implementation and assessment. The purpose of this component is to implement the four interventions developed in the preceding component, assess their effects and whether they are cost effective. A longitudinal quasi-experimental design will be used. Intervention monitoring will extend over 12 months. The effects will be assessed by means of generalized estimating equation regressions. A cost-benefit analysis will be performed to assess the cost-effectiveness of the interventions, taking an institutional perspective (costs and benefits associated with the intervention). (3) Analysis of co-construction and implementation process. The purpose of this component is to (1) describe and assess the approaches used to engage stakeholders in the co-construction and implementation process; (2) identify the factors that have fostered or impeded the co-construction, implementation and long-term sustainability of the interventions. The proposed design is a longitudinal multiple case study. DISCUSSION: In the four participating institutions, the project will provide an opportunity to develop new abilities that will strengthen team resilience and create more suitable work environments. Beyond these institutions, the project will generate a variety of resources (e.g.: work situation analysis tools; method of operationalizing the intervention co-development process; communications tools; assessment tools) that other oncology teams will be able to adapt and deploy elsewhere.

Perceived Effectiveness and Motivations for the Use of Web-Based Mental Health Programs: Qualitative Study.

BACKGROUND: The prevalence of depression is high and has been stable despite increased treatment, research, and dissemination. People encounter barriers to seeking traditional mental health services, which could be mitigated by using web-based prevention methods. OBJECTIVE: This study aims to understand what people at high risk for depression perceive as effective aspects of web-based mental health programs and what motivates people at high risk for depression to use web-based mental health programs. METHODS: We conducted an inductive content analysis using telephone interview data from 77 participants at high risk for depression who were recruited from 2 randomized controlled trials (RCTs). Participants from the first RCT were working men who had been randomly assigned to 1 of the following 3 groups: control group, who had access to general depression information from a website called BroMatters; intervention group 1, who had access to the BroMatters website along with the associated BroHealth web-based mental health program; and intervention group 2, who had access to the BroMatters website, the BroHealth web-based mental health program, and telephone sessions with a life coach. Participants from the second RCT were men and women who had been assigned to the intervention group, who received access to the HardHat web-based mental health program, or the control group, who only received access to the HardHat web-based mental health program following completion of the RCT. Participants for this inductive content analysis study were recruited from the intervention groups in both RCTs. Two groups of participants (n=41 and n=20) were recruited from the BroHealth RCT, and a third group comprised 16 participants that were recruited from the HardHat RCT. RESULTS: We generated four categories regarding the perceived effectiveness of web-based programs and five categories related to what motivates the use of web-based programs. Participants identified awareness, program medium and functionality, program content, and coaches as categories related to the effectiveness of the programs. Categories of motivators to use web-based programs included providing reminders or incentives, promotion of the programs, providing appropriate medium and functionality, appropriate content, and perceived need. The final category related to motivators reflects perceptions of participants who were either unsure about what motivates them or believed that there is no way to motivate use. CONCLUSIONS: Conflicting evidence was obtained regarding the perceived effectiveness of aspects of the content and functionality of web-based programs. In general, web-based mental health programs were perceived to help increase mental health awareness, especially when it includes live access to a coach. However, the results also revealed that it is difficult to motivate people to begin using web-based mental health programs. Strategies that may motivate the use of such programs include perceived personal need, effective promotion, providing incentives and reminders, and improving functionality.

The effect of high-fat diet consumption on appetitive instrumental behavior in rats.

Evidence now indicates that the chronic consumption of high-calorie foods, such as a high-fat diet (HFD), is associated with impaired control over food-seeking, yet the extent of this alteration is not fully understood. Using different reinforcement schedules, we evaluated whether HFD intake from weaning to adulthood modifies instrumental responding and induces a shift from goal-directed actions to habitual responding. We first observed reduced instrumental performance and motivation for a food reward in HFD-fed rats trained under schedules of reinforcement that facilitate habitual responding [Random Interval (RI)]. However, this deficit was alleviated if rats trained under RI were subsequently trained with reinforcement schedules that promote goal-directed strategies [Random Ratio (RR)]. Using an outcome devaluation procedure, we then demonstrated that consumption of a HFD promoted habitual behavior in rats trained under RI but not RR schedules. Finally, extended HFD exposure did not interfere with the ability of RR training to overcome impaired RI instrumental performance and to favor goal-directed behavior. These results indicate that chronic consumption of a HFD changes the co-ordination of goal-directed actions and habits and that alteration of food-seeking may be reversed under particular behavioral conditions.

[A typology of mental health comorbidity in workplaces: results from the SALVEO study]. / Une typologie de la comorbidité en santé mentale au travail : résultats de l'étude SALVEO.

Objectives The aim of this study consists in describing the nature of mental health comorbidity among workers. Precisely, we seek to examine the presence of concomitant associations between burnout (cynicism, emotional exhaustion, professionnal inefficacy) and psychoactive substance use (heavy episodic drinking, above low-risk drinking guidelines, and psychotropic drug use).Methods The SALVEO study is based on a cross-sectional sample of 1966 workers from the province of Québec, Canada. Latent class analyses were performed in order to identify typical patterns corresponding to distinct forms of mental health comorbidity in the data. Multinomial logistic regressions on latent classes were performed using covariables pertaining to work and non-work domains and workers' individual characteristics.Results Four typical patterns in mental health comorbidity were found: 1- "Severe burnout and psychotropic drug use"; 2- "At risk drinking and cynicism"; 3- "Emotional exhaustion and professional inefficacy"; and 4- "Relatively healthy state". Of all four patterns, the "Severe burnout and psychotropic drug use" pattern presented the highest number of cumulative risks (environmental and individual).Conclusion Comorbidity in mental health is a matter of importance in workplaces from the province of Québec. The severity in the different patterns of mental health comorbidity expressed a cumulative effect of risk factors from the work and non-work domains, as well as individual characteristics.

Flexible Use of Predictive Cues beyond the Orbitofrontal Cortex: Role of the Submedius Thalamic Nucleus.

The orbitofrontal cortex (OFC) is known to play a crucial role in learning the consequences of specific events. However, the contribution of OFC thalamic inputs to these processes is largely unknown. Using a tract-tracing approach, we first demonstrated that the submedius nucleus (Sub) shares extensive reciprocal connections with the OFC. We then compared the effects of excitotoxic lesions of the Sub or the OFC on the ability of rats to use outcome identity to direct responding. We found that neither OFC nor Sub lesions interfered with the basic differential outcomes effect. However, more specific tests revealed that OFC rats, but not Sub rats, were disproportionally relying on the outcome, rather than on the discriminative stimulus, to guide behavior, which is consistent with the view that the OFC integrates information about predictive cues. In subsequent experiments using a Pavlovian contingency degradation procedure, we found that both OFC and Sub lesions produced a severe deficit in the ability to update Pavlovian associations. Altogether, the submedius therefore appears as a functionally relevant thalamic component in a circuit dedicated to the integration of predictive cues to guide behavior, previously conceived as essentially dependent on orbitofrontal functions. Significance statement: In the present study, we identify a largely unknown thalamic region, the submedius nucleus, as a new functionally relevant component in a circuit supporting the flexible use of predictive cues. Such abilities were previously conceived as largely dependent on the orbitofrontal cortex. Interestingly, this echoes recent findings in the field showing, in research involving an instrumental setup, an additional involvement of another thalamic nuclei, the parafascicular nucleus, when correct responding requires an element of flexibility (Bradfield et al., 2013a). Therefore, the present contribution supports the emerging view that limbic thalamic nuclei may contribute critically to adaptive responding when an element of flexibility is required after the establishment of initial learning.

Juvenile obesity enhances emotional memory and amygdala plasticity through glucocorticoids.

In addition to metabolic and cardiovascular disorders, obesity is associated with adverse cognitive and emotional outcomes. Its growing prevalence during adolescence is particularly alarming since recent evidence indicates that obesity can affect hippocampal function during this developmental period. Adolescence is a decisive period for maturation of the amygdala and the hypothalamic-pituitary-adrenal (HPA) stress axis, both required for lifelong cognitive and emotional processing. However, little data are available on the impact of obesity during adolescence on amygdala function. Herein, we therefore evaluate in rats whether juvenile high-fat diet (HFD)-induced obesity alters amygdala-dependent emotional memory and whether it depends on HPA axis deregulation. Exposure to HFD from weaning to adulthood, i.e., covering adolescence, enhances long-term emotional memories as assessed by odor-malaise and tone-shock associations. Juvenile HFD also enhances emotion-induced neuronal activation of the basolateral complex of the amygdala (BLA), which correlates with protracted plasma corticosterone release. HFD exposure restricted to adulthood does not modify all these parameters, indicating adolescence is a vulnerable period to the effects of HFD-induced obesity. Finally, exaggerated emotional memory and BLA synaptic plasticity after juvenile HFD are alleviated by a glucocorticoid receptor antagonist. Altogether, our results demonstrate that juvenile HFD alters HPA axis reactivity leading to an enhancement of amygdala-dependent synaptic and memory processes. Adolescence represents a period of increased susceptibility to the effects of diet-induced obesity on amygdala function.

Parallel inputs from the mediodorsal thalamus to the prefrontal cortex in the rat.

There is a growing interest in determining the functional contribution of thalamic inputs to cortical functions. In the context of adaptive behaviours, identifying the precise role of the mediodorsal thalamus (MD) in particular remains difficult despite the large amount of experimental data available. A better understanding of the thalamocortical connectivity of this region may help to capture its functional role. To address this issue, this study focused exclusively on the specific connections from the MD to the prefrontal cortex (PFC) by means of direct comparisons of labelling produced by single and dual injections of retrograde tracers in the different subdivisions of the PFC in the rat. We show that at least three parallel and essentially separate thalamocortical pathways originate from the MD, as follows: projections to the dorsal (1) and the ventral (2) subdivisions of the mPFC follow a mediolateral topography at the thalamic level (i.e. medial thalamic neurons target the mPFC ventrally whereas lateral thalamic neurons project dorsally), whereas a considerable innervation to the OFC (3) includes thalamic cells projecting to both the lateral and the ventral OFC subdivisions. These observations provide new insight on the functions of the MD and suggest a specific focus on each of these pathways for future functional studies.

A time course analysis of satiety-induced instrumental outcome devaluation.

Sensory-specific satiety is commonly used in studies of decision making to selectively devalue a food reward. Devaluation is reflected in an immediate reduction in the subsequent intake of the food and in the performance of actions that gain access to that food. Despite its frequent use, the lasting effects of satiety-induced devaluation on instrumental actions are unknown. Here, we examined the time course and contextual dependency of sensory-specific satiety-induced devaluation on instrumental responding and consumption. Rats were trained to perform two instrumental actions for two distinct food rewards. Then, one of the instrumental outcomes was provided ad libitum for 1 hour in separate feeding cages and the effect of this devaluation was assessed 0, 2, or 5 hours after satiation. At a delay of 0 or 2 hours, both intake and instrumental responding were sensitive to the satiety treatment. That is, rats consumed less of the devalued outcome and responded less for the devalued outcome than for the valued outcome. By contrast, after 5 hours, rats showed sensitivity to devaluation in consumption but not in instrumental responding. Strikingly, sensitivity to devaluation was restored for the instrumental response after a 5 hour delay when devaluation was performed in the instrumental context. These results indicate that, in rats, specific satiety-induced devaluation endures and is context-independent for up to 2 hours post-satiation. At longer delays, the impact of sensory-specific satiety on instrumental responding is context-dependent, suggesting that contextual cues may be required for the value of specific outcomes to control instrumental responding.

Preferred Features of E-Mental Health Programs for Prevention of Major Depression in Male Workers: Results From a Canadian National Survey.

BACKGROUND: Major depression is a prevalent mental disorder and imposes considerable burden on health and productivity. Men are not immune to major depression, yet they often delay seeking help because of perceived stigma and gender norms. E-mental health programs hold potential for early prevention of major depression. However, we have little knowledge about men's preferences for design features of e-mental health programs. OBJECTIVES: The objective of this study was to (1) estimate and compare the proportions of Internet use for medical information, preferred design features, and likely use of e-mental health programs; (2) examine factors associated with the likely use of e-mental health programs; and (3) understand potential barriers to the use of e-mental health programs among Canadian working men, who were at high risk of a major depressive episode (MDE). METHODS: A cross-sectional survey in 10 Canadian provinces was conducted between March and December 2015. Random digit dialing method was used through household landlines and cell phones to collect data from 511 working men who were at high risk of having an MDE and 330 working men who were at low risk of having an MDE. RESULTS: High-risk men were more likely to endorse the importance of accessing health resources on the Internet than low-risk men (83.4% vs 75.0%, respectively; P=.01). Of the 17 different features assessed, the top three features most likely to be used by high-risk men were: "information about improving sleep hygiene" (61.3%), "practice and exercise to help reduce symptoms of stress and depression" (59.5%), and "having access to quality information and resources about work stress issues" (57.8%). Compared with men at low risk for MDE, men at high risk for MDE were much more likely to consider using almost every one of the different design features. Differences in preferences for the design features by age among men at high risk of MDE were found only for 3 of 17 features. Differences in preferences for design features between English- and French-speaking participants were found only for 4 out of the 17 features. Analysis of qualitative data revealed that privacy issues, perceived stigma, ease of navigation, personal relevance, and lack of personal interaction, time, and knowledge were identified as barriers to the use of e-mental health programs in working men who were at high risk of MDE. CONCLUSION: E-mental health programs may be a promising strategy for prevention of depression in working men. Development of e-mental health programs should consider men's preferences and perceived barriers to enhance the acceptability of this approach.

Mediodorsal but not anterior thalamic nuclei lesions impair acquisition of a conditional discrimination task.

The limbic thalamus is a heterogeneous structure with distinctive cortical connectivity. A recent review suggests that the mediodorsal thalamic nucleus (MD), unlike the anterior thalamic nuclei (ATN), may be involved in selecting relevant information in tasks relying on executive functions. We compared the effects of excitotoxic lesions of the MD or the ATN on the acquisition of a simple conditional discrimination in rats. When required to choose from two levers according to auditory or visual cues, ATN rats and sham-lesioned rats performed to the same levels and displayed similar acquisition curves. Under the same conditions, MD rats' acquisition of the task was markedly delayed. This group nevertheless attained nearly normal performances after more extensive training. Furthermore, all rats learned reversal of the original discrimination at the same rate. These results highlight functional specialization within the limbic thalamus and support the notion that MD contributes to the identification of relevant dimensions in conditional tasks during the initial stages of acquisition.

The multilevel determinants of workers' mental health: results from the SALVEO study.

PURPOSE: This study examined the contribution of work, non-work and individual factors on workers' symptoms of psychological distress, depression and emotional exhaustion based on the multilevel determinants of workers' mental health model. METHODS: Data from the SALVEO Study were collected in 2009-2012 from a sample of 1,954 employees nested in 63 workplaces in the province of Quebec (Canada). Multilevel regression models were used to analyse the data. RESULTS: Altogether, variables explain 32.2 % of psychological distress, 48.4 % of depression and 48.8 % of emotional exhaustion. Mental health outcomes varied slightly between workplaces and skill utilisation, physical and psychological demands, abusive supervision, interpersonal conflicts and job insecurity are related to the outcomes. Living in couple, having young children at home, family-to-work conflict, work-to-family conflict, strained marital and parental relations, and social support outside the workplace associated with the outcomes. Most of the individual characteristics also correlated with the three outcomes. Importantly, non-work and individual factors modulated the number and type of work factors related to the three outcomes. CONCLUSION: The results of this study suggest expanding perspectives on occupational mental health that fully recognise the complexity of workers' mental health determinants.

Psychological distress in the workforce: a multilevel and longitudinal analysis of the case of regulated occupations in Canada.

BACKGROUND: This study uses a multidimensional theoretical model to evaluate the role of regulated occupations and working conditions in explaining psychological distress. METHODS: Various multilevel regression analyses were conducted on longitudinal data for which measures repeated over time (n1 = 36,166) were nested in individuals (n2 = 7007). RESULTS: Results showed that when we controlled for working conditions, family situation, the social network outside the workplace, and personal characteristics, the level of psychological distress was significantly lower among professional workers in regulated occupations than among professionals not in regulated occupations. Among the working conditions studied, skill utilisation, psychological demands, and job insecurity were positively associated with psychological distress levels, whereas social support in the workplace was inversely related to distress. Finally, our results suggest that self-esteem reduced the effect of social support in the workplace on psychological distress levels in the workforce. CONCLUSIONS: These results support our hypothesis that working in regulated occupations exerts a direct effect on mental health. These results also make clear the importance of developing new tools for measuring psychological distress among upper-level professional workers. Such tools will be much better suited to the realities characterising today's knowledge-based economies.

Parallel maturation of goal-directed behavior and dopaminergic systems during adolescence.

Adolescence is a crucial developmental period characterized by specific behaviors reflecting the immaturity of decision-making abilities. However, the maturation of precise cognitive processes and their neurobiological correlates at this period remain poorly understood. Here, we investigate whether a differential developmental time course of dopamine (DA) pathways during late adolescence could explain the emergence of particular executive and motivational components of goal-directed behavior. First, using a contingency degradation protocol, we demonstrate that adolescent rats display a specific deficit when the causal relationship between their actions and their consequences is changed. When the rats become adults, this deficit disappears. In contrast, actions of adolescents remain sensitive to outcome devaluation or to the influence of a pavlovian-conditioned stimulus. This aspect of cognitive maturation parallels a delayed development of the DA system, especially the mesocortical pathway involved in action adaptation to rule changes. Unlike in striatal and nucleus accumbens regions, DA fibers and DA tissue content continue to increase in the medial prefrontal cortex from juvenile to adult age. Moreover, a sustained overexpression of DA receptors is observed in the prefrontal region until the end of adolescence. These findings highlight the relationship between the emergence of specific cognitive processes, in particular the adaptation to changes in action consequences, and the delayed maturation of the mesocortical DA pathway. Similar developmental processes in humans could contribute to the adolescent vulnerability to the emergence of several psychiatric disorders characterized by decision-making deficits.

A role for anterior thalamic nuclei in affective cognition: interaction with environmental conditions.

Damage to anterior thalamic nuclei (ATN) is a well-known cause of diencephalic pathology that produces a range of cognitive deficits reminiscent of a hippocampal syndrome. Anatomical connections of the ATN also extend to cerebral areas that support affective cognition. Enriched environments promote recovery of declarative/relational memory after ATN lesions and are known to downregulate emotional behaviors. Hence, the performance of standard-housed and enriched ATN rats in a range of behavioral tasks engaging affective cognition was compared. ATN rats exhibited reduced anxiety responses in the elevated plus maze, increased activity and reduced corticosterone responses when exploring an open field, and delayed acquisition of a conditioned contextual fear response. ATN rats also exhibited reduced c-Fos and phosphorylated cAMP response element-binding protein (pCREB) immunoreactivity in the hippocampal formation and the amygdala after completion of the contextual fear test. Marked c-Fos hypoactivity and reduced pCREB levels were also evident in the granular retrosplenial cortex and, to a lesser extent, in the anterior cingulate cortex. Unlike standard-housed ATN rats, enriched ATN rats expressed virtually no fear of the conditioned context. These results show that the ATN regulate affective cognition and that damage to this region may produce markedly different behavioral effects as a function of environmental housing conditions.

Work hours and cortisol variation from non-working to working days.

PURPOSE: This study aims at modelling the relationship between the number of work hours per week and cortisol variation across 3 days by comparing non-working day to working day in a population of day-shift workers. METHODS: Questionnaire data and saliva samples for cortisol analysis were collected on 132 day-shift workers employed in 13 workplaces in Canada. Consenting workers provided 5 saliva samples a day (awaking, 30 min after awaking, 2 p.m., 4 p.m., bedtime) repeated 3 times (Saturday, Tuesday, Thursday) over a week, to provide measures at work and non-work times and settings. Multilevel regression models were estimated from cortisol measurements at each occasion within a day at level-1, days at level-2 and workers at level-3. RESULTS: Controlling for gender and age, results revealed significant variations in salivary cortisol concentration between sample, day and worker levels. Cortisol increases linearly from non-working day to work days and work hours per week interacted with days, revealing a positive association between the number of work hours per week and cortisol concentrations during these days. Work hours per week did not interact with awaking, 30 min after awaking, 2 p.m., 4 p.m., and bedtime cortisol concentrations. Gender and age had neither main effects nor interaction effects. No significant cortisol variations were found between workplaces. CONCLUSION: These results suggest that work hours act as a stressor that is associated with significant variations in cortisol concentrations over working days. Non-working days may contribute to stress reduction in workers who experience longer work hours.

Quantitative analysis of organizational culture in occupational health research: a theory-based validation in 30 workplaces of the organizational culture profile instrument.

BACKGROUND: This study advances a measurement approach for the study of organizational culture in population-based occupational health research, and tests how different organizational culture types are associated with psychological distress, depression, emotional exhaustion, and well-being. METHODS: Data were collected over a sample of 1,164 employees nested in 30 workplaces. Employees completed the 26-item OCP instrument. Psychological distress was measured with the General Health Questionnaire (12-item); depression with the Beck Depression Inventory (21-item); and emotional exhaustion with five items from the Maslach Burnout Inventory general survey. Exploratory factor analysis evaluated the dimensionality of the OCP scale. Multilevel regression models estimated workplace-level variations, and the contribution of organizational culture factors to mental health and well-being after controlling for gender, age, and living with a partner. RESULTS: Exploratory factor analysis of OCP items revealed four factors explaining about 75% of the variance, and supported the structure of the Competing Values Framework. Factors were labeled Group, Hierarchical, Rational and Developmental. Cronbach's alphas were high (0.82-0.89). Multilevel regression analysis suggested that the four culture types varied significantly between workplaces, and correlated with mental health and well-being outcomes. The Group culture type best distinguished between workplaces and had the strongest associations with the outcomes. CONCLUSIONS: This study provides strong support for the use of the OCP scale for measuring organizational culture in population-based occupational health research in a way that is consistent with the Competing Values Framework. The Group organizational culture needs to be considered as a relevant factor in occupational health studies.