Franziska Plessow

Classification Criteria for Distinguishing Cortisol Responders From Nonresponders to Psychosocial Stress: Evaluation of Salivary Cortisol Pulse Detection in Panel Designs

Objective Hypothalamic-pituitary-adrenal axis reactivity to acute stimulation is frequently assessed by repeated sampling of salivary cortisol. Researchers often strive to distinguish between individuals who show (responders) and those do not show (nonresponders) cortisol responses. For this, fixed threshold classification criteria, such as a 2.5-nmol/l baseline-to-peak increase, are frequently used. However, the performance of such criteria has not been systematically evaluated. Methods Repeated salivary cortisol data from 504 participants exposed to either the Trier Social Stress Test (TSST; n = 309) or a placebo protocol (n = 195) were used for analyses. To obtain appropriate classifications of cortisol responders versus nonresponders, a physiologically plausible, autoregressive latent trajectory (ALT) mixture model was fitted to these data. Response classifications according to the ALT model and information on the experimental protocol (TSST versus placebo TSST) were then used to evaluate the performance of different proposed classifier proxies by receiver operating characteristics. Results Moment structure of cortisol time series was adequately accounted for by the proposed ALT model. The commonly used 2.5-nmol/l criterion was found to be overly conservative, resulting in a high rate of 16.5% false-negative classifications. Lowering this criterion to 1.5 nmol/l or using a percentage baseline-to-peak increase of 15.5% as a threshold yielded improved performance (39.3% and 26.7% less misclassifications, respectively). Conclusions Alternative classification proxies (1.5 nmol/l or 15.5% increase) are able to effectively distinguish between cortisol responders and nonresponders and should be used in future research, whenever statistical response class allocation is not feasible.

Inflexibly focused under stress: Acute psychosocial stress increases shielding of action goals at the expense of reduced cognitive flexibility with increasing time lag to the stressor

Dynamically adjusting the right amount of goal shielding to varying situational demands is associated with the flexibility of cognitive control, typically linked with pFC functioning. Although stress hormones are found to also bind to prefrontal receptors, the link between stress and cognitive control remains elusive. Based on that, we aimed at investigating effects of acute psychosocial stress on dynamic control adjustments. Forty-eight healthy volunteers were exposed to either a well-established stress induction protocol (the Trier Social Stress Test, TSST) or a standardized control situation before a selective attention (Simon) task involving response conflicts. The individual physiological stress response was monitored by analyzing levels of free cortisol and α-amylase activity in saliva samples showing that the TSST reliably induced an increase of endogenous stress hormone levels. Acute stress did not inevitably impair cognitive functioning, however, as stressed participants showed tonically increased goal shielding (to reduce interference) at the expense of decreased cognitive flexibility. Importantly, as a novel finding in humans, stress effects on cognitive functions were not present immediately after the stress experience but developed gradually over time and, therefore, paralleled the time course of the hypothalamus–pituitary–adrenal (HPA) stress response. In addition, the total increase of individual cortisol levels reflecting HPA activity, but not the total changes in α-amylase activity associated with sympathetic activity, was reversely related to the amount of cognitive flexibility in the final block of testing. Our study provides evidence for a stress-induced time-dependent decrease of cognitive flexibility that might be related to changes in cortisol levels.

Psychoendocrine and psychoneuroimmunological mechanisms in the comorbidity of atopic eczema and attention deficit/hyperactivity disorder

Epidemiological data indicate that atopic eczema (AE) in infancy significantly increases the risk for attention deficit/hyperactivity disorder (ADHD) in later life. The underlying pathophysiological mechanisms of this comorbidity are unknown. We propose that the release of inflammatory cytokines caused by the allergic inflammation and/or elevated levels of psychological stress as a result of the chronic disease interfere with the maturation of prefrontal cortex regions and neurotransmitter systems involved ADHD pathology. Alternatively, increased stress levels in ADHD patients may trigger AE via neuroimmunological mechanisms. In a third model, AE and ADHD may be viewed as two separate disorders with one or more shared risk factors (e.g., genetics, prenatal stress) that increase the susceptibility for both disorders leading to the co-occurrence of AE and ADHD. Future investigation of these three models may lead to a better understanding of the mechanisms underlying the observed comorbidity between AE and ADHD and further, to targeted interdisciplinary primary prevention and treatment strategies.

Comparison of salivary cortisol as measured by different immunoassays and tandem mass spectrometry

Assessing the amount of bioavailable cortisol in saliva with immunoassays and thus sampling an endocrine marker of hypothalamus-pituitary-adrenal axis activity is of major interest in both research and clinical practice. However, absolute cortisol concentrations obtained with different immunoassays (IAs) are barely comparable precluding direct comparison between studies or individuals whenever cortisol analyses were not based on the same IA. The present technical report aims to solve this problem by evaluating the validity of, as well as agreement between the most commonly used immunoassays in psychoneuroendocrinological research (i.e., IBL, DRG, Salimetrics, DSL, and DELFIA) and a reference method (LC-MS/MS) in a sample of 195 saliva specimen covering the whole range of cortisol concentrations in adults. A structural equation modelling framework is applied to decompose systematic assay variance and estimate cortisol reference values, which are adjusted for measurement error and interference of salivary cortisone. Our findings reveal nonlinear relations between IAs and LC-MS/MS, which are discussed in terms of IA cross-reactivity with saliva matrix components. Finally guidelines for converting cortisol concentrations being obtained by these immunoassays into comparable reference values are proposed by providing conversion functions, a conversion table, and an online conversion tool.

Response to Comment on "Estimating the reproducibility of psychological science"

Gilbert et al. conclude that evidence from the Open Science Collaboration’s Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.

Transformation techniques for cross-sectional and longitudinal endocrine data: Application to salivary cortisol concentrations

Endocrine time series often lack normality and homoscedasticity most likely due to the non-linear dynamics of their natural determinants and the immanent characteristics of the biochemical analysis tools, respectively. As a consequence, data transformation (e.g., log-transformation) is frequently applied to enable general linear model-based analyses. However, to date, data transformation techniques substantially vary across studies and the question of which is the optimum power transformation remains to be addressed. The present report aims to provide a common solution for the analysis of endocrine time series by systematically comparing different power transformations with regard to their impact on data normality and homoscedasticity. For this, a variety of power transformations of the Box-Cox family were applied to salivary cortisol data of 309 healthy participants sampled in temporal proximity to a psychosocial stressor (the Trier Social Stress Test). Whereas our analyses show that un- as well as log-transformed data are inferior in terms of meeting normality and homoscedasticity, they also provide optimum transformations for both, cross-sectional cortisol samples reflecting the distributional concentration equilibrium and longitudinal cortisol time series comprising systematically altered hormone distributions that result from simultaneously elicited pulsatile change and continuous elimination processes. Considering these dynamics of endocrine oscillations, data transformation prior to testing GLMs seems mandatory to minimize biased results.

Better Not to Deal with Two Tasks at the Same Time When Stressed? Acute Psychosocial Stress Reduces Task Shielding in Dual-Task Performance

A major control demand in successful dual-task performance is the task-specific separation of task-goal representations and of the related stimulus–response translation processes. In the present study, we investigated how these cognitive control processes of task shielding are affected by acute psychosocial stress. Fifty-six healthy participants were exposed to either an acute psychosocial stressor (the Trier Social Stress Test) or a standardized control situation prior to a dual task. Task shielding was assessed by analyzing the interference of Task 2 processing on prioritized Task 1 performance. Following successful stress induction, as indicated by increases in salivary α-amylase (sAA) and cortisol that reflect increases in sympathetic nervous system and hypothalamus–pituitary–adrenal (HPA) axis activity, respectively, stressed individuals displayed reduced task shielding relative to controls. This result was further substantiated by a correlation between treatment-related increase in cortisol, but not sAA, and between-task interference, suggesting a potential role of the HPA stress response for the development of the observed effects. As an additional finding, when the volunteers were categorized with regard to their action–state orientation, their orientation did not interact with stress but did reveal generally increased between-task interference, and thus inferior task shielding, for state-oriented as compared to action-oriented individuals.

Stress Reduces Use of Negative Feedback in a Feedback-Based Learning Task

In contrast to the well-established effects of stress on learning of declarative material, much less is known about stress effects on reward- or feedback-based learning. Differential effects on positive and negative feedback especially have received little attention. The objective of this study, thus, was to investigate effects of psychosocial stress on feedback-based learning with a particular focus on the use of negative and positive feedback during learning. Participants completed a probabilistic selection task in both a stress and a control condition. The task allowed quantification of how much participants relied on positive and negative feedback during learning. Although stress had no effect on general acquisition of the task, results indicate that participants used negative feedback significantly less during learning after stress compared with the control condition. An enhancing effect of stress on use of positive feedback failed to reach significance. These findings suggest that stress acts differentially on the use of positive and negative feedback during learning.

Auditory Warning Signals Affect Mechanisms of Response Selection Evidence from a Simon Task

Irrelevant tone (accessory) stimuli facilitate performance in simple and choice reaction time tasks. In the present study, we combined accessory stimulation with a selective attention paradigm in order to investigate its influence on mechanisms of response selection. In the framework of a spatial stimulus-response compatibility task (Simon task), we tested whether accessory stimuli selectively affect bottom up triggered response activation processes (e.g., direct route processing), processing of task-relevant stimulus features (indirect route processing), or both/none. Results suggest a two-component effect of accessory stimuli within this selective attention task. First, accessory stimuli increased the Simon effect due to beneficial direct route processing. Second, accessory stimuli generally decreased reaction times indicating facilitation of indirect route processing.

Efficient multitasking: parallel versus serial processing of multiple tasks

In the context of performance optimizations in multitasking, a central debate has unfolded in multitasking research around whether cognitive processes related to different tasks proceed only sequentially (one at a time), or can operate in parallel (simultaneously). This review features a discussion of theoretical considerations and empirical evidence regarding parallel versus serial task processing in multitasking. In addition, we highlight how methodological differences and theoretical conceptions determine the extent to which parallel processing in multitasking can be detected, to guide their employment in future research. Parallel and serial processing of multiple tasks are not mutually exclusive. Therefore, questions focusing exclusively on either task-processing mode are too simplified. We review empirical evidence and demonstrate that shifting between more parallel and more serial task processing critically depends on the conditions under which multiple tasks are performed. We conclude that efficient multitasking is reflected by the ability of individuals to adjust multitasking performance to environmental demands by flexibly shifting between different processing strategies of multiple task-component scheduling.