Fingernail cortisol - State of research and future directions

The impact of marriage equality campaigns on stress: Did a Swiss public vote get under the skin?

Lesbian, gay, bisexual, trans, intersex, and queer (LGBTIQ+) individuals encounter persistent structural inequalities and discrimination that can lead to detrimental psychological and physiological health outcomes. Amid evolving legal landscapes, little attention has been directed toward understanding the physiological health effects of societal shifts on these communities. This study aims to explore the impact of a national marriage equality vote and associated debates on psychological and biological stress among LGBTIQ+ individuals and cisgender, heterosexual, endosex individuals (termed cis-heterosexual) in Switzerland. We gathered longitudinal survey and biological data collected in hair samples among LGBTIQ+ and cis-heterosexual individuals before, during, and after the 2021 national vote (survey data: NT1T2 = 954; NT2T3 = 880; biological data: NT1T2 = 393; NT2T3 = 354). Preregistered analyses reveal a notable increase in biological stress levels (i.e., cortisol and cortisone levels), but not perceived stress, among both LGBTIQ+ as well as cis-heterosexual individuals who were close to them during the campaign. Results further point out the negative impacts of the campaign against marriage equality (i.e., no-campaign) on LGBTIQ+ individuals' biological stress levels as well as on those of their allies. These effects were, however, moderated by exposure to the campaign for marriage equality (i.e., yes-campaign), indicating the powerful buffering effects of the yes-campaign on the impact of discrimination on individuals' health. However, these positive effects appear to come at a cost, potentially impacting the well-being of individuals engaged in advocating for the yes-campaign. This research underscores the lasting impact of political campaigns on individuals' health.

Midlife symptoms and household stress are associated with fingernail cortisol

OBJECTIVE

This study investigates menopausal symptoms, household stressors, and ethnopolitical problems in relation to stress markers, including chronic stress measured by fingernail cortisol, perceived stress measured by the Perceived Stress Scale, and acute stress measured by blood pressure.

METHODS

Data from 151 women aged 40 to 55 years were collected from four regions in Nagaland, India, using opportunity sampling. A structured questionnaire was used to collect sociodemographic and lifestyle variables. Symptoms were grouped into emotional instability, vasosomatic symptoms, mood disturbances, and aches and pains using principal component analysis in a previous study, and stress markers included fingernail cortisol, perceived stress, and blood pressure. Community-level, household-level, and midlife symptoms were included to ascertain stressors from different sources.

RESULTS

Our results revealed a significant positive association between a composite measure of emotional instability and stress assessed by fingernail cortisol ( β = 0.46, P < 0.001). In addition, there was a positive association between mood disturbances and fingernail cortisol ( β = 0.24, P < 0.05). This relationship persisted after controlling for body mass index, socioeconomic status, and menopausal status. In addition, household problems were positively associated with fingernail cortisol ( β = 0.25, P = 0.01).

CONCLUSIONS

These findings highlight the potential health impacts of the psychosocial stress response associated with domestic stressors such as financial strain and concerns about children and health.

Time-course changes in fingernail cortisol levels during pregnancy and postpartum

The cortisol level in fingernails can reflect the cumulative hormones produced in the body several months prior. However, previous studies have only demonstrated the cross-sectional associations of fingernail cortisol with salivary or hair cortisol, and not longitudinal changes in fingernail cortisol in situations where cortisol levels in the body could be expected to change. Therefore, this study focused on pregnancy as a model for changes in cortisol levels over a prolonged period of time, and investigating the time courses of fingernail cortisol during pregnancy and the postpartum period. We collected nail samples from 30 healthy women during pregnancy and 12 months postpartum to measure the cortisol levels in the nail. Results showed that cortisol levels in fingernail clippings increased from 1 month before childbirth to 4 months postpartum, with the levels peaking at 2 months postpartum. Additionally, we found higher cortisol levels in fingernail clippings in primiparas than in those of multiparas. The time course of fingernail cortisol levels could replicate the longitudinal changes in cortisol in the body, and differences between multiparas and primiparas seemed to be biologically plausible, which could support the concept of fingernail cortisol as a retrospective index of hormone production.

Fingernail Cortisol: A Biological Signal of Lifetime Major Depressive Disorder

INTRODUCTION

Elevated levels of the hypothalamic-pituitary-adrenal axis hormone cortisol are a frequently replicated finding in major depressive disorder (MDD). However, the current state of research is inconclusive as to whether hypercortisolism represents a trait- or state-like biological signal of MDD. The aim of the present study was to investigate, for the first time, whether cortisol in fingernails, a highly accessible tissue, could distinguish currently remitted individuals with MDD from healthy controls. A further aim was to identify potential confounders of nail cortisol.

METHODS

A total of N = 100 individuals from the general population were recruited. A structured clinical interview was administered, which resulted in two groups: n = 48 with lifetime MDD and n = 52 healthy controls. All participants answered questions on sociodemographic, lifestyle, and psychosocial characteristics. They also grew their nails for 14 days and cut them for the subsequent determination of cortisol.

RESULTS

The groups differed in their nail cortisol concentrations, such that the individuals with lifetime MDD had significantly higher concentrations than the healthy controls (p = 0.041). Within the group of individuals with lifetime MDD, the number of experienced episodes was significantly correlated with cortisol (p = 0.011). Income emerged as the only significant confounder of cortisol (p = 0.008).

CONCLUSION

Elevated fingernail cortisol appears to be a biological signal of MDD, even in the absence of a current major depressive episode. Its high accessibility and robustness render it a promising methodology for remote research as well as for the integration of biomarkers into clinical research and practice.

Associations between hair cortisol and blood pressure: a systematic review and meta-analysis

OBJECTIVE

Stress is widely considered to be a risk factor for high blood pressure (BP), but evidence on the associations between biomarkers of chronic stress and BP is inconsistent. This systematic review and meta-analysis assessed the current state of the science on relationships between measures of cortisol concentration reflecting chronic stress exposure [hair cortisol concentration (HCC), nail cortisol concentration)] and BP.

METHODS

PubMed, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Cochrane Library, and Embase were searched. Random effects models were used to assess the pooled effect size. Exploratory moderation analysis was performed.

RESULTS

Out of 34 014 identified, 16 articles met eligibility criteria and were included in the review, while 14 were included in the meta-analysis. No articles were reported on the association between nail cortisol concentration and BP. Small, positive associations were observed between HCC and SBP [ r  = 0.19 (95% confidence interval (CI): 0.08-0.29)] and HCC and DBP [ r  = 0.13 (95% CI: 0.04-0.22)]. Cortisol analysis method was identified as a significant moderator of the association between HCC and DBP. HCC was largely, positively associated with hypertension status [odds ratio = 3.23 (95% CI: 2.55-4.09), P  < 0.001].

CONCLUSIONS

Current evidence suggests that higher HCC may be associated with elevated BP and a potential risk factor for hypertension. However, results should be interpreted with caution because HCC can be affected by hair color, hair care products, and analytic methods. Given the limitations of studies included in this review, further research is needed.

Feasibility of remote self-collection of dried blood spots, hair, and nails among people with HIV with hazardous alcohol use

BACKGROUND

The use of biomarkers in behavioral HIV research can help to address limitations of self-reported data. The COVID-19 pandemic forced many researchers to transition from standard in-person data collection to remote data collection. We present data on the feasibility of remote self-collection of dried blood spots (DBS), hair, and nails for the objective assessment of alcohol use, antiretroviral therapy adherence, and stress in a sample of people with HIV (PWH) who are hazardous drinkers.

METHODS

Standardized operating procedures for remote self-collection of DBS, hair, and nails were developed for an ongoing pilot study of a transdiagnostic alcohol intervention for PWH. Prior to each study appointment, participants were mailed a kit containing materials for self-collection, instructions, a video link demonstrating the collection process, and a prepaid envelope for returning samples.

RESULTS

A total of 133 remote study visits were completed. For DBS and nail collection at baseline, 87.5% and 83.3% of samples, respectively, were received by the research laboratory, of which 100% of samples were processed. Although hair samples were intended to be analyzed, most of the samples (77.7%) were insufficient or the scalp end of the hair was not marked. We, therefore, decided that hair collection was not feasible in the framework of this study.

CONCLUSION

An increase in remote self-collection of biospecimens may significantly advance the field of HIV-related research, permitting the collection of specimens without resource-intensive laboratory personnel and facilities. Further research is needed on the factors that impeded participants' ability to complete remote biospecimen collection.

Cortisol Immunosensors: A Literature Review

Cortisol is a steroid hormone that is involved in a broad range of physiological processes in human/animal organisms. Cortisol levels in biological samples are a valuable biomarker, e.g., of stress and stress-related diseases; thus, cortisol determination in biological fluids, such as serum, saliva and urine, is of great clinical value. Although cortisol analysis can be performed with chromatography-based analytical techniques, such as liquid chromatography-tandem mass spectrometry (LC-MS/MS), conventional immunoassays (radioimmunoassays (RIAs), enzyme-linked immunosorbent assays (ELISAs), etc.) are considered the "gold standard" analytical methodology for cortisol, due to their high sensitivity along with a series of practical advantages, such as low-cost instrumentation, an assay protocol that is fast and easy to perform, and high sample throughput. Especially in recent decades, research efforts have focused on the replacement of conventional immunoassays by cortisol immunosensors, which may offer further improvements in the field, such as real-time analysis at the point of care (e.g., continuous cortisol monitoring in sweat through wearable electrochemical sensors). In this review, most of the reported cortisol immunosensors, mainly electrochemical and also optical ones, are presented, focusing on their immunosensing/detection principles. Future prospects are also briefly discussed.

Minimally invasive biomarkers in human and non-human primate evolutionary biology: Tools for understanding variation and adaptation

BACKGROUND

The use of minimally invasive biomarkers (MIBs - physiological biomarkers obtained from minimally invasive sample types) has expanded rapidly in science and medicine over the past several decades. The MIB approach is a methodological strength in the field of human and non-human primate evolutionary biology (HEB). Among humans and our closest relatives, MIBs provide unique opportunities to document phenotypic variation and to operationalize evolutionary hypotheses.

AIMS

This paper overviews the use of MIBs in HEB. Our objectives are to (1) highlight key research topics which successfully implement MIBs, (2) identify promising yet under-investigated areas of MIB application, and (3) discuss current challenges in MIB research, with suggestions for advancing the field.

DISCUSSION AND CONCLUSIONS

A range of MIBs are used to investigate focal topics in HEB, including energetics and life history variation/evolution, developmental plasticity, and social status and dominance relationships. Nonetheless, we identify gaps in existing MIB research on traits such as physical growth and gut function that are central to the field. Several challenges remain for HEB research using MIBs, including the need for additional biomarkers and methods of assessment, robust validations, and approaches that are standardized across labs and research groups. Importantly, researchers must provide better support for adaptation and fitness effects in hypothesis testing (e.g., by obtaining complementary measures of energy expenditure, demonstrating redundancy of function, and performing lifetime/longitudinal analyses). We point to continued progress in the use of MIBs in HEB to better understand the past, present, and future of humans and our closest primate relatives.

Applying minimally invasive biomarkers of chronic stress across complex ecological contexts

Chronic stress is both theoretically and methodologically challenging to operationalize through biomarkers. Yet minimally invasive, field-friendly biomarkers of chronic stress are valuable in research linking biology and culture, seeking to understand differential patterns of human development across ecological contexts, and exploring the evolution of human sociality. For human biologists, a central question in measurement and interpretation of biomarkers is how stress-responsive physiological systems are regulated across diverse human ecologies. This article aims to describe a conditional toolkit for human biologists interested in the study of chronic stress, highlighting a mix of longstanding and novel biomarkers, with special focus on hair/fingernail cortisol, latent herpesvirus antibodies, allostatic load indices, and serial/ambulatory data collection approaches. Future trends in chronic stress biomarker research, including epigenetic approaches, are briefly considered. This overview considers: (1) challenges in separating a distinctly psychosocial dimension of chronic stress from adversity more broadly; (2) essential characteristics of human ecology that shape interpretation; (3) retrospective vs. longitudinal sampling; (4) the role of age, developmental effects, and local biologies; (5) different timescales of chronicity; and (6) the role of culture.

Biological markers in clinical psychological research - A systematic framework applied to HPA axis regulation in PTSD

Biological markers, particularly endocrine measurements, are increasingly being integrated into clinical psychological research. We introduce a systematic framework that classifies different functions of such biomarkers. The framework distinguishes between diagnostic biomarkers which add a biological perspective to conventional clinical assessments, prognostic biomarkers that inform about an individual’s risk to develop or maintain a mental health disorder, and intervention-related biomarkers. Regarding interventions, including prevention and treatment, it further distinguishes between prescriptive biomarkers which predict an individual’s response to an intervention, outcome biomarkers which evaluate intervention-related changes on a biological level and indicators of change mechanisms. We demonstrate how to apply the framework by exemplarily classifying and describing previously published systematic reviews and primary empirical studies on endogenous, peripheral cortisol concentrations as a biomarker for posttraumatic stress disorder (PTSD). The evidence on cortisol’s diagnostic and prognostic value is heterogeneous and still sparse regarding parameters based on multiple cortisol measurements, such as the cortisol awakening response. With regard to interventions, most research focused on trauma-focused psychotherapy and cortisol reactivity to trauma reminders. This field of research appears to be growing and very promising due to its potential to optimize PTSD-related interventions. The proposed framework can help in gaining a systematic overview of existing research. It can assist in structuring, comparing, summarizing and evaluating empirical studies, and in identifying research gaps.

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Iagnostic biomarkers can inform about biological alterations in mental disorders.

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Prognostic biomarkers can help to predict the development of a mental disorder.

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Biomarkers can indicate the outcome, differential effects, or mechanisms of change of clinical psychological interventions.

Endocannabinoid and steroid analysis in infant and adult nails by LC-MS/MS

A common method to quantify chronic stress is the analysis of stress markers in keratinized matrices such as hair or nail. In this study, we aimed to validate a sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the combined quantification of steroid hormones and endocannabinoids (eCBs) in the keratinized matrix nail. Furthermore, we aimed to investigate the suitability of the nail matrix for the detection of these stress markers in a pilot study. An LC–MS/MS method was used for the simultaneous identification and quantification of four eCBs (2-arachidonoylglycerol (2-AG), anandamide (AEA), oleoylethanolamide (OEA), palmitoylethanolamide (PEA)) and five steroid hormones (cortisol, cortisone, androstenedione, progesterone, testosterone) in human nails using a surrogate analyte method for each analyte. The method was validated in terms of selectivity, response factor, linearity, limit of quantification (LOQ), precision, accuracy, matrix effect, recovery, robustness, and autosampler stability. Nail samples were extracted for 1 h with methanol following a clean-up with a fully automated supported liquid extraction (SLE). The influence of nail weight on the quantification was investigated by using 0.5–20 mg of nail sample. As a proof of concept, nail samples (N = 57) were analyzed from a cohort representing newborns (1 month old), children (between 1 and 10 years), and adults (up to 43 years). It could be shown that the established workflow using a 1 hour extraction and clean-up by SLE was very robust and resulted in a short sample preparation time. The LC–MS/MS method was successfully validated. Matrix effects with ion enhancement occurred mainly for 2-AG. Sample weights below 5 mg showed variations in quantification for some analytes. Certain analytes such as PEA and progesterone could be accurately quantified at a sample weight lower than 5 mg. This is the first study where steroids and eCBs could be simultaneously detected and quantified in infant and adult nails. These results show that nails may serve as an alternative keratinized matrix (compared to hair) for the retrospective monitoring of cumulative eCB and steroid hormone levels. The combined assessment of eCBs and steroids from nails could provide a new approach to gain new insights into stress exposure in newborns and adults.

Selection of appropriate biomatrices for studies of chronic stress in animals: a review

Cortisol and corticosterone, hormones traditionally considered biomarkers of stress, can be measured in fluid biomatrices (e.g., blood, saliva) from live animals to evaluate conditions at sampling time, or in solid biomatrices (e.g., hair, feather) from live or dead animals to obtain information regarding long-term changes. Using these biomarkers to evaluate physiological stress responses in domestic animals may be challenging due to the diverse characteristics of biomatrices for potential measurement. Ideally, a single measurement from the biomatrix should be sufficient for evaluating chronic stress. The availability of appropriate and cost-effective immunoassay methods for detecting the biomarkers should also be considered. This review discusses the strengths and limitations of different biomatrices with regard to ensuring the highest possible reliability for chronic stress evaluation. Overall, solid biomatrices require less frequent sampling than other biomatrices, resulting in greater time- and cost-effectiveness, greater ease of use, and fewer errors. The multiplex immunoassay can be used to analyze interactions and correlations between cortisol and other stress biomarkers in the same biomatrix. In light of the lack of information regarding appropriate biomatrices for measuring chronic stress, this review may help investigators set experimental conditions or design biological research.

Hair cortisol levels in women with medically unexplained symptoms

Stress has been demonstrated to be involved in the development of medically unexplained symptoms. A key underlying mechanism could be lower levels of cortisol, which can contribute to symptoms such as fatigue or pain. However, the literature is highly equivocal, which may be due to methodological limitations inherent in short-term cortisol assessment. The aim of this case-control study was to investigate, for the first time, whether individuals with different forms of medically unexplained symptoms show altered hair cortisol concentrations, a long-term marker of hypothalamic-pituitary-adrenal functioning. Two groups of women with medically unexplained symptoms were recruited. The first had a functional somatic syndrome, characterised by specific medically unexplained symptoms (i.e., chronic fatigue syndrome, fibromyalgia, or irritable bowel syndrome, n = 33). The second had somatic symptom disorder, characterised by excessive thoughts, feelings, and behaviours devoted to various medically unexplained symptoms (n = 23). These groups were contrasted with healthy controls (n = 30), and women with depression (n = 27). Cortisol representing the previous three months was extracted from hair. Chronic stress and childhood trauma were assessed (retrospectively). Women with somatic symptom disorder had lower hair cortisol than healthy controls and women with functional somatic syndromes. No differences in hair cortisol were found between healthy controls, functional somatic syndromes, and depression. Neither childhood trauma nor chronic stress was correlated with hair cortisol. Provided that our findings are replicated, they may suggest that hypocortisolism is found in a specific subgroup of individuals with medically unexplained symptoms, and potentially in those characterised by excessive thoughts, feelings, and behaviours about symptoms.

Patient and Therapist In-Session Cortisol as Predictor of Post-Session Patient Reported Affect

The importance of the role of affect in psychotherapy for major depressive disorder (MDD) is well established, but the common use of self-reported measures may limit our understanding of its underlying mechanisms. A promising predictor of patient affect is the stress hormone cortisol. To date, no studies have studied in-session changes in cortisol in psychotherapy for MDD. We investigated whether an increase in patient cortisol over the course of a session correlated with higher negative and lower positive affect. Given previous findings on healthy individuals on the contagious nature of stress, an additional aim was to examine whether these relationships are moderated by therapist cortisol. To this end, 40 dyads (including 6 therapists) provided saliva samples before and after four pre-specified sessions (616 samples). After each session, the patients provided retrospective reports of in-session affect. We found no association between patient cortisol and affect. However, increases in patient cortisol predicted negative affect when the therapists exhibited decreases in cortisol, and increases in patient cortisol predicted positive affect when the therapists showed increases. Our study provides initial evidence for the importance of the social context in the cortisol-affect relationship in MDD.

Biomarkers of disease in human nails: a comprehensive review

Diagnostic, monitoring, response, predictive, risk, and prognostic biomarkers of disease are all widely studied, for the most part in biological fluids or tissues, but there is steadily growing interest in alternative matrices such as nails. Here we comprehensively review studies dealing with molecular or elemental biomarkers of disease, as opposed to semiological, pharmacological, toxicological, or biomonitoring studies. Nails have a long history of use in medicine as indicators of pathological processes and have also been used extensively as a matrix for monitoring exposure to environmental pollution. Nail clippings are simple to collect noninvasively as well as to transport and store, and the matrix itself is relatively stable. Nails incorporate, and are influenced by, circulating molecules and elements over their several months of growth, and it is widely held that markers of biological processes will remain in the nail, even when their levels in blood have declined. Nails thus offer the possibility to not only look back into a subject's metabolic history but also to study biomarkers of processes that operate over a longer time scale such as the post-translational modification of proteins. Reports on ungual biomarkers of metabolic and endocrine diseases, cancer, and psychological and neurological disorders will be presented, and an overview of the sampling and analytical techniques provided.