Chronic stress and executive functioning: A specification-curve analysis.

To investigate the association between chronic stress and executive functioning (EF), we assessed 514 young to middle-aged adults in three EF tasks (i.e., Number-Letter, 2-Back, Go/Nogo) that assessed shifting, updating, and inhibition. Chronic stress was assessed by various self-report measures and hair cortisol concentrations as indicators of subjective and objective chronic stress, respectively. In order to test the association between chronic stress and EF, we fit a structural equation model with a latent common EF factor predicted by subjective and objective chronic stress on Kaplan-Meier estimates of response times. Controlling for participants' sex, age household income and the delay between cognitive testing and hair sample collection, neither subjective nor objective chronic stress showed a meaningful association with common EF. Exploratory analyses suggested a moderation effect of income on the association between subjective chronic stress and common EF, with a smaller association for high-income participants. Additionally, we conducted a specification-curve analysis on the association between chronic stress and EF to assess the influence of different analysis choices on results in our dataset. This analysis confirmed the absence of a coherent association between chronic stress and EF by showing that the majority of analytical choices produced null effects and only a small number of analytical choices produced meaningful associations (negative or positive). Taken together, our findings suggest that common EF likely remains preserved under the influence of chronic stress. Our specification-curve analysis, however, also shows that chronic stress may also have either a positive or a negative effect on EF, depending on the choice of covariates and measures of chronic stress and EF. Consequently, more research on the role of these factors for the association between chronic stress and EF is needed to avoid the interpretation of non-replicable stress-EF associations caused by analytical choices or selection bias.

Intra-individual stability of hair endocannabinoid and N-acylethanolamine concentrations.

Hair analysis of endocannabinoids and N-acylethanolamines presents a promising methodological advancement for the retrospective assessment of long-term cumulative endocannabinoids and N-acylethanolamines secretion over extended periods of time. A main assumption of this method application that hair endocannabinoid and N-acylethanolamine concentrations show intra-individual stability has not been confirmed yet. Thus, in the current study hair endocannabinoid and N-acylethanolamine levels were measured over a period of two and a half years with six months between each hair sample collection in 100 female participants. We found strong test-retest associations of hair endocannabinoid and N-acylethanolamine levels with intraclass correlation coefficients between 0.79 and 0.92. Furthermore, no correlations between perceived stress and hair endocannabinoids or N-acylethanolamines was observed. The current findings support the notion that endocannabinoids and N-acylethanolamines in hair are rather trait biomarkers that are stable over a considerable period of time rather than rapidly changing state markers.

Temporal stability and effect dynamics between executive functions, perceived chronic stress, and hair cortisol concentrations.

Accidents caused by human errors illustrate the fragility of cognitive processing and its coordination by executive functions against stress. To better understand how core executive functions change over time, influence each other, and are affected by chronic stress exposure, a prospective cohort study was conducted from 2016 to 2019. Five hundred sixteen German adults aged 25-55 years (mean age/education age: 38.0/11.3 years, 67% females, 94% occupied, 20% smokers) completed at least one internet-based biannual assessment of response inhibition, updating, and set shifting using a Go/NoGo, spatial 2-Back, and Number-Letter task, respectively. Chronic stress exposure was indicated by self-reports on the Perceived Stress Scale (PSS) and hair cortisol concentrations (HCC). Statistical analyses were performed by multivariate stochastic differential equation modeling. All indicators of executive functions (task-specific RTs in target trials or their contrast to nontarget trials) and chronic stress showed intraindividual stability over time (12% to 63% of their variance was attributable to trait influences). With respect to lagged mutual associations, faster Go/NoGo target RTs predicted faster Number-Letter target RTs later in time, while faster Number-Letter target RTs predicted higher HCC later in time (both with maximum effect sizes of d ≈ 0.1 standard deviations). However, PSS was not predictive of later HCC and vice versa. None of the chronic stress indicators significantly predicted indicators of executive functions at subsequent time points. These findings suggest that set shifting is capable of modulating the body's physiological response to chronic stress exposure, whereas executive functions appear comparably robust against chronic stress exposure. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

How to deal with non-detectable and outlying values in biomarker research: Best practices and recommendations for univariate imputation approaches.

Non-detectable (ND) and outlying concentration values (OV) are a common challenge of biomarker investigations. However, best practices on how to aptly deal with the affected cases are still missing. The high methodological heterogeneity in biomarker-oriented research, as for example, in the field of psychoneuroendocrinology, and the statistical bias in some of the applied methods may compromise the robustness, comparability, and generalizability of research findings. In this paper, we describe the occurrence of ND and OV in terms of a model that considers them as censored data, for instance due to measurement error cutoffs. We then present common univariate approaches in handling ND and OV by highlighting their respective strengths and drawbacks. In a simulation study with lognormal distributed data, we compare the performance of six selected methods, ranging from simple and commonly used to more sophisticated imputation procedures, in four scenarios with varying patterns of censored values as well as for a broad range of cutoffs. Especially deletion, but also fixed-value imputations bear a high risk of biased and pseudo-precise parameter estimates. We also introduce censored regressions as a more sophisticated option for a direct modeling of the censored data. Our analyses demonstrate the impact of ND and OV handling methods on the results of biomarker-oriented research, supporting the need for transparent reporting and the implementation of best practices. In our simulations, the use of imputed data from the censored intervals of a fitted lognormal distribution shows preferable properties regarding our established criteria. We provide the algorithm for this favored routine for a direct application in R on the Open Science Framework (https://osf.io/spgtv). Further research is needed to evaluate the performance of the algorithm in various contexts, for example when the underlying assumptions do not hold. We conclude with recommendations and potential further improvements for the field.

Comparison of hair cortisol concentrations between self- and professionally-collected hair samples and the role of five-factor personality traits as potential moderators.

Cortisol concentration of hair (HCC) is an established biomarker in stress research that can provide valuable retrospective information on subjects' long-term cortisol levels. Using a population-wide sample of in total N = 482 participants this study aimed to examine whether there are differences in HCC when participants collect the required samples by themselves with the help of a partner in domestic settings compared to professionally collected hair strands in the lab. Potential confounding factors that may affect HCC and might obfuscate the outcomes were considered. The results suggest that the two compared sample collection methods did not significantly differ from each other in terms of HCC (p = .307). A somewhat larger sample loss in the domestic setting was observed due to hair samples where HCC could not be determined (5.3 % vs. 1.8 % in the lab). Similarly, in a sample of N = 50 using a within-subjects design (Sample 2) no significant HCC differences between collection methods occurred (p = .206). In addition, potential moderating effects of personality traits of the Five-Factor-Model on the relationship between hair collection method and HCC were investigated. In Sample 1 personality data of the hair donor were available, while in Sample 2 personality data (n = 40) were available for the hair donor and the hair sample collector. Interestingly, none of the Big Five traits significantly moderated the relationship between HCC and hair collection method (all p > .20). Overall, these findings suggest that the self-collection of hair in domestic settings is a viable and economical method for measuring long-term cortisol concentrations in hair.

Reconsidering the construct validity of self-reported chronic stress: A multidimensional item response theory approach.

Emerging evidence shows that the construct validity of commonly used chronic stress measures is questionable. Item response theory was used to evaluate the psychometric properties of the Perceived Stress Questionnaire (PSQ), the Perceived Stress Scale (PSS), and the Screening Scale of Chronic Stress (SSCS). Using multidimensional item response modeling of data from two population-based samples (N1 = 5,379, N2 = 504), we identified and conceptually replicated a five-dimensional model combining items of chronic stress, neuroticism (i.e., Big Five Inventory Neuroticism scale; BFI-N), and depressiveness (i.e., Patient Health Questionnaire depressiveness scale; PHQ-9). The findings suggested a major overlap of variance between items of the applied instruments forming a pronounced common latent scale, which appeared to be mainly based on the perceived extent of freely available energy (i.e., vitality vs. fatigue). Accordingly, the overlap between items of the PSQ, PSS, and SSCS was larger with PHQ-9 items than BFI-N items. Specifically, items of chronic stress seem to discriminate subclinical manifestations of fatigue, a core symptom of depressiveness. Subsequently estimated person parameters were used to predict hair cortisol concentrations (HCC), a physiological indicator of chronic stress. Controlling for potential confounders, only the common latent scale showed a weak association with HCC, whereas residual variance components were not predictive of HCC. This finding further supports the notion that instruments like PSQ, PSS, and SSCS show an impaired construct validity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The psychometric properties and temporal dynamics of subjective stress, retrospectively assessed by different informants and questionnaires, and hair cortisol concentrations.

To date, there is only scarce evidence for a considerable association of subjective and objective stress measures, which might be attributable to method bias (e.g., confounding) and/or asynchrony of their temporal changes. To validate different subjective stress measures by a physiological measure of long-term stress (hair cortisol concentrations; HCC), 37 heterosexual couples (N = 74) completed a 12-week internet-based assessment protocol comprised of a weekly hassle scale (WHS; once per week), a perceived stress scale (PSS; once per month), and a chronic stress scale (TICS; once after three months). Partners provided vicarious stress ratings. When averaged across time, self-reported WHS significantly predicted HCC (r = 0.27), whereas the PSS and TICS did not (r < 0.22). Dynamic factor analysis (i.e., state-space modelling) confirmed that WHS was the most valid indicator of subjective stress, explaining up to 16% of the variance in HCC (r = 0.37) with a time lag of ~4 weeks. This temporally delayed effect of subjective stress is consistent with the presumed retrospective character of HCC, but also suggests that the majority of variance in hair cortisol is attributable to other causes than subjective stress such as individual disposition to display increased adrenocortical activity.