Background: Early life stress is a common problem in today's society, and it has been shown to lead to a variety of psychological and somatic conditions in adulthood. This is believed to be partly...Show moreBackground: Early life stress is a common problem in today's society, and it has been shown to lead to a variety of psychological and somatic conditions in adulthood. This is believed to be partly due to chronically enhanced physiological stress levels, irrespective of stressors experienced in adult life. According to a new stress theory, the Generalized Unsafety Theory of Stress (GUTS), chronic stress is the result of a chronically disinhibited stress response as a result of a general sense of unsafety rather than the cumulative effects of everyday stressors. Early life stress might lead to developing such a sense of generalized unsafety by disrupting safety learning in close relationships, better known as insecure attachment. Insecure attachment potentially induces long-term dysregulation of the HPA axis that can lead to chronically high levels of cortisol, majorly contributing to somatic health complaints in adulthood. Purpose: This meta-analysis is the first one to systematically examine the connection between an insecure attachment and chronic high cortisol levels in later life, with the aim to provide a better understanding of the ways early life experiences can have detrimental effects on our long-term health and wellbeing. The broader aim of this paper is to find supportive evidence for the theoretical framework of the GUTS. Methods: The Web of Science database was searched for eligible studies using an exhaustive keyword profile. Articles were included only if they used a physically and psychologically healthy adult or child population, measured resting or baseline levels of cortisol and attachment style later in life and reported statistical analyses of the relationship between attachment styles and cortisol levels. The program Comprehensive Meta-Analysis was used to determine an overall correlation coefficient representing this association. Results: A small but significant association was found between adult insecure attachment and baseline cortisol levels later in life (r = 0.199, p < 0.001). Differential analyses of types of insecure attachment revealed that attachment anxiety had a significant contribution to the association, while attachment avoidance did not. Conclusion: Insecure attachment is related to a higher resting level of cortisol. In this way, it seems to play a moderate but potentially important role in chronic stress later in life. This role is more attributable to higher levels of attachment-related anxiety than attachment-related avoidance. The findings partially support the theoretical framework of GUTS, however, also raise points for debate.Show less
Background: Having a low socioeconomic status (SES) and limited access to green space is associated with negative health effects. From the perspective of the Generalized Unsafety Theory of Stress ...Show moreBackground: Having a low socioeconomic status (SES) and limited access to green space is associated with negative health effects. From the perspective of the Generalized Unsafety Theory of Stress (GUTS), people who live in such a compromised social and physical context suffer from a constant default stress response. We hypothesized that low SES and lack of neighborhood green space are both associated with higher levels of chronic stress, measured in hair cortisol concentration. Hair cortisol is the first objective biomarker for chronic stress, which is increasingly used in research. Objectives: The objective of this meta-analysis was to assess whether chronic stress due to low socioeconomic status and/or lack of green environment can be recognized in hair cortisol levels. Method: Systematic literature search of the Web of Science database yielded 5 relevant papers for green space and 19 papers for socioeconomic status. Random-effect meta-analyses were conducted for each outcome, where after meta-regression analyses were performed for possible moderators. Results: Analyzing five studies (n = 641) showed that more green space was associated with lower hair cortisol concentration (r = -.17, p < .001). The 19 studies of SES (n = 6023) contained 30 subsamples, based on the SES indicators: education, income, and total SES score. A higher income was significantly associated with lower hair cortisol concentration (r = -.11, p < .001). No associations were found between hair cortisol and education (r = -.06, p = .10), and total SES (r = .02, p = .85). Due to the lack of articles including green environment and SES, we could not analyze their relative contribution as well as their interaction effect on hair cortisol. Conclusions: These findings suggest that people with a higher income, and more neighborhood green space have lower levels of chronic stress. These outcomes contribute to the existing research about health disparities and the role of chronic stress, while also adding to the growing body of hair cortisol research as an objective and non-invasive stress biomarker. Future research is recommended with diverse samples including socioeconomic status and neighborhood green space, to gain a better understanding on the impact of individual and environmental factors on chronic stress.Show less
Background - The Generalised Unsafety Theory of Stress, a novel stress explanation, considers the stress response as a default mode of the body, which is always active independently from stressors...Show moreBackground - The Generalised Unsafety Theory of Stress, a novel stress explanation, considers the stress response as a default mode of the body, which is always active independently from stressors unless it is inhibited based on perceiving safety. GUTS suggests there are compromised domains where stress is chronically released despite a lack of clear stressors, and the organism is unable to inhibit the stress mechanism mostly because of perceiving generalised unsafety around. One of these compromised domains is believed to be urban environments as they cannot provide sufficient signs of safety, and they mainly consist property of strangers. Natural environments in contrast are believed to provide signs of safety and therefore decrease stress levels. Using meta-analysis, this current research aimed to find and summarize evidence from existing studies reporting that urban environments are associated with increased levels of stress, Method - In total, 12 studies, collected from Web of Science database, were included in six meta-analyses conducted on heart rate variability (high frequency, low frequency/high frequency), saliva cortisol, blood pressure (systolic and diastolic), and heart rate data of healthy adult participants during and after exposure to urban and natural environments. Results - Statistically significant increased heart rate was found after a walk in the urban environment (g = 0.37, 95% CI: 0.20; 0.50, p <0.0001). High frequency heart rate variability was significantly lower after an urban walk(unknown baseline balance group: g = -0.33, 95% CI: -0.55; -0.11; baseline balanced: g = -2.52, 95% CI: -3.25; -1.78). Low frequency heart rate variability was significantly higher during the urban walk (unknown baseline balance group: g = 0.33, 95% CI: 0.49; 1.80; baseline balanced: g = 2.52, 95% CI: 1.78; 3.26). Subgroup analyses and funnel plots for heart rate variability showed a possible small-study effect in the baseline balanced groups. Blood pressure and cortisol measurements showed no significant effect and were ambiguous because of high heterogeneity and small number of included studies. Conclusions - Heart rate variability and heart rate measures indicated a higher stress level in urban than in natural environments providing an example of prolonged stress without stressors, explainable by GUTS. For blood pressure and cortisol no such evidence was provided. However, the results should be carefully interpreted because of high between-study heterogeneity and other limitations of these studies. Further research into stress measurements and effects of natural and urban environment on stress are required to provide reliable evidence.Show less
Research master thesis | Psychology (research) (MSc)
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Background: Loneliness is widely experienced by the population and is related to several negative health effects. These effects may be partly due to enhanced activation of the stress response,...Show moreBackground: Loneliness is widely experienced by the population and is related to several negative health effects. These effects may be partly due to enhanced activation of the stress response, despite the lack of frequently occurring stressors in loneliness that are commonly believed to explain stress responses. However, according to a new stress theory (GUTS), the stress response is a default response, which is only turned off when safety cues are present. In loneliness the primary source of social safety is missing, which might explain an increased stress response, which can be measured by looking at the cortisol awakening response (CAR). Purpose: Testing, using meta-analysis, the positive effect of loneliness on the CAR and whether this is moderated by age or duration of loneliness. Methods: Eligible studies were sought using a keyword profile in Web of Science. A random-effects meta-analysis was performed to study the relationship between loneliness and the CAR, meta-regression analyses were performed to study the effect of possible moderators. Results: Six studies (n = 1,396) were included in the meta-analysis. No significant positive relationship between loneliness and the CAR was found. Also, no moderating effect of age on the relationship was found. The moderating effect of duration of loneliness could not be studied due to missing information. The results suggested a negative relationship between loneliness and the CAR. Conclusion: Although the hypotheses were not confirmed, several important implications for future research are given, such as the need to incorporate duration of loneliness and conformation to general guidelines in assessing the CAR. Further research is needed to draw definite conclusions about the relation between loneliness and the CAR and about what it means for the GUTS.Show less
Background: Long-term exposure to road traffic noise is associated with the prevalence of hypertension. To understand more about this exposure-response relationship, it is essential to examine this...Show moreBackground: Long-term exposure to road traffic noise is associated with the prevalence of hypertension. To understand more about this exposure-response relationship, it is essential to examine this association with baseline blood pressure measurements. However, theories of possible mechanisms explaining the chronic physiological effects of road traffic noise exposure are limited. Furthermore, the findings of epidemiological studies investigating this relationship are inconsistent and different factors seem to influence the strength of the relationship. A critical evaluation of these studies seems warranted. Purpose: This study aims to gain more theoretical and empirical insight into the association between road traffic noise and resting blood pressure measurements. Methods: Web of Science, PubMed and reference lists were used. Six articles were included, consisting of information about ten studies. A meta-analysis on the association between road traffic noise and blood pressure among adults was performed. The ten effect size estimates were based on the data of 146,339 subjects in total. Results: A 0.195 mmHg (95% CI: 0.004, 0.386) higher systolic blood pressure per 10 dB increase was found. Road traffic noise was not associated with diastolic blood pressure. However, the sensitivity analysis revealed stronger associations with diastolic blood pressure for high-quality studies and stronger associations with systolic blood pressure for nighttime noise exposure. Conclusion: Long-term exposure to road traffic noise had a significant positive association with systolic blood pressure, perhaps strongest at night, and a nonsignificant positive association with diastolic blood pressure. The significant moderating effect of study quality on diastolic blood pressure is a possible explanation for this inconsistency. Further research is required to get a more comprehensive understanding of the association between road traffic noise and blood pressure.Show less
