Joanne Bradbury

Modelling stress constructs with biomarkers: the importance of the measurment model

Joanne Bradbury — Wed, 16 Jan 2013 14:11:12 PST

Background The transactional model of stress describes a psychological and physiological stress response that is elicited when an environmental demand is perceived to out-weigh the ability to cope with the demand. With perception at its core, this theory explains large variances in human stress responses. A frequently cited measure of stress perception is the Perceived Stress Scale (PSS). A two-step approach to structural equation modelling (SEM) necessitates that a valid measurement model for stress be first established through confirmatory factor analysis (CFA), and then the impact of stress on the biomarkers be assessed. Methods The aims of this study were to explore and confirm the factorial structure of the 10-item PSS (PSS-10) in a sample of healthy Australians (n = 194) and to cross-validate it in an independent sample (n = 117) of healthy Australians with chronic work stress, and to explore the impact of stress on the production of the ex vivo stimulated secretion of proinflammatory cytokines, interleukins IL-1β, IL-6 and tumour necrosis factor (TNFα), using SEM. As only Sample 1 had data on both PSS scores and proinflammatory cytokine secretion, SEM would be confined to Sample 1. Results Perceived Stress was found to have different factorial structures in the different samples. In Sample 1, it was best represented by three correlated factors; Overwhelmed (items 2, 10, 6, 8), Coping (items 4, 7, 5), and Emotional Reactivity (items 1, 9, 3). This three-factor model for was not cross-validated in Sample 2, which fit the two-factor model reported in the literature. The SEM suggested that the three factors predicted significant differential effects on proinflammatory cytokines that were less evident for the two-factor model. Conclusions These findings demonstrate that if the measurement model does not adequately represent the relationship structures within the data, differential effects on biomarkers may be diluted by larger measurement errors. This analysis has highlighted the importance of testing the assumptions of the measurement model used to represent stress in human populations. Further research is required to determine whether the construct known as perceived stress comprises two or three inherent factors in population norms.

The effectiveness of narrative therapy with young people with autism

Andrew Cashin et al. — Wed, 19 Sep 2012 18:25:13 PDT

Problem The aim of this pilot study was to be the first step toward empirically determining whether narrative therapy is effective in helping young people with autism who present with emotional and behavioral problems. Autism is increasingly being recognized in young people with average and above intelligence. Because of the nature of autism, these young people have difficulty navigating the challenges of school and adolescence. Narrative therapy can help them with their current difficulties and also help them develop skills to address future challenges. Narrative therapy involves working with a person to examine and edit the stories the person tells himself or herself about the world. It is designed to promote social adaptation while working on specific problems of living. Method This pilot intervention study used a convenience sample of 10 young people with autism (10–16 years) to evaluate the effectiveness of five 1 hr sessions of narrative therapy conducted over 10 weeks. The study used the parent-rated Strengths and Difficulties Questionnaire (SDQ) as the primary outcome measure. Secondary outcome measures were the Kessler-10 Scale of Psychological Distress (K-10), the Beck Hopelessness Scale, and a stress biomarker, the salivary cortisol to dehydroepiandrosterone (DHEA) ratio. Findings Significant improvement in psychological distress identified through the K-10 was demonstrated. Significant improvement was identified on the Emotional Symptoms Scale of the SDQ. The cortisol:DHEA ratio was responsive and a power analysis indicated that further study is indicated with a larger sample. Conclusion Narrative therapy has merit as an intervention with young people with autism. Further research is indicated.

Are low-fat diets associated with stress?

Joanne Bradbury — Thu, 19 Jul 2012 18:37:49 PDT

Background: The purpose of this study was to confirm the evidence that low-fat diets are associated with stress and negative mood states. Methods: Four self-report stress and mood measures were correlated with a crude dietary fat screen in 93 university staff that responded to an advertisement for a stress and dietary fats study. The screen was a modification of two previously validated dietary assessment questionnaires. The three stress measures were the Perceived Stress Scale (PSS), the Occupational Stress Inventory - Revised (OSI-R), and a visual analogue scale (VAS). The mood scale was the Positive and Negative Affect Scale (PANAS). Subjects completed the questionnaires at two measuring points, with a 10-week interval. Results: At Time 1 there was an inverse correlation between fish intake and vocational strain (r= -0.30, p

Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain

Joanne Bradbury — Thu, 19 Jul 2012 18:37:48 PDT

Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high-quality, easily digested nutrients from coastal seafood and inland freshwater sources. Multi-generational exploitation of seafood by shore-based dwellers coincided with the rapid expansion of grey matter in the cerebral cortex, which characterizes the modern human brain. The DHA molecule has unique structural properties that appear to provide optimal conditions for a wide range of cell membrane functions. This has particular implications for grey matter, which is membrane-rich tissue. An important metabolic role for DHA has recently been identified as the precursor for resolvins and protectins. The rudimentary source of DHA is marine algae; therefore it is found concentrated in fish and marine oils. Unlike the photosynthetic cells in algae and higher plants, mammalian cells lack the specific enzymes required for the de novo synthesis of alpha-linolenic acid (ALA), the precursor for all omega-3 fatty acid syntheses. Endogenous synthesis of DHA from ALA in humans is much lower and more limited than previously assumed. The excessive consumption of omega-6 fatty acids in the modern Western diet further displaces DHA from membrane phospholipids. An emerging body of research is exploring a unique role for DHA in neurodevelopment and the prevention of neuropsychiatric and neurodegenerative disorders. DHA is increasingly being added back into the food supply as fish oil or algal oil supplementation.

Are the adaptogenic effects of omega 3 fatty acids mediated via inhibition of proinflammatory cytokines?

Joanne Bradbury et al. — Wed, 18 Jul 2012 04:03:15 PDT

The study was undertaken to estimate the size of the impact of n-3 fatty acids in psychological stress and the extent to which it is mediated via proinflammatory cytokines. Structural equation modeling (SEM) was used to analyze data from 194 healthy Australians. Biomarkers used were erythrocyte polyunsaturated fatty acids (docosahexaenoic acid (DHA) and arachidonic acid (AA)), ex-vivo stimulated secretion of proinflammatory cytokines (interleukins (IL-1 and IL-6), and tumor necrosis factor (TNF)). Stress was measured with the perceived stress scale (PSS-10), found to comprise three factors: Coping (items 4, 7, 5), Overwhelm (2, 10, 6 and 8), and Emotional (1, 9 and 3). This modeling demonstrated that the effects of DHA on coping are largely direct effects (0.26, 𝑡 = 2 . 0 5) and were not significantly mediated via the suppression of proinflammatory cytokines. Future modeling should explore whether adding EPA to the model would increase the significance of the mediation pathways.

Global slowdown in the fast lane

Stephen P. Myers et al. — Wed, 18 Jul 2012 04:03:11 PDT

The article examines the reasons for the increasing levels of stress being experienced among Australians. The ongoing recession leading to job uncertainty appears to be some of the reasons for work-stress believed to be one of the causes of late-life dementia.

An adaptogenic role for omega-3 fatty acids in stress; a randomised placebo controlled double blind intervention study (pilot) [ISRCTN22569553]

Joanne Bradbury et al. — Wed, 18 Jul 2012 03:14:42 PDT

Background There is evidence for an adaptive role of the omega -3 fatty acid, docosahexaenoic acid (DHA) during stress. Mechanisms of action may involve regulation of stress mediators, such as the catecholamines and proinflammatory cytokines. Prevention of stress-induced aggression and hostility were demonstrated in a series of clinical trials. This study investigates whether perceived stress is ameliorated by DHA in stressed university staff.

Methods Subjects that scored ≥ 17 on the Perceived Stress Scale were randomised into a 6-week pilot intervention study. The diet reactive group was supplemented with 6 g of fish oil containing 1.5 g per day DHA, while the placebo group was supplemented with 6 g a day of olive oil. The groups were compared with each other and a wider cross sectional study population that did not receive either active or placebo intervention.

Results There was a significant reduction in perceived stress in both the fish oil and the placebo group from baseline. There was also a significant between-group difference between the fish oil group and the no-treatment controls in the rate of stress reduction (p < 0.05). However, there was not a significant between-group difference between the fish oil and the placebo group, nor the placebo group and the control group.

These results are discussed in the context of several methodological limitations. The significant stress reductions in both the fish oil and the placebo group are considered in view of statistical regression, an effect likely to have been exaggerated by the time course of the study, a large placebo effect and the possibility of an active effect from the placebo.

Conclusion There were significant differences (p < 0.05) in the fish oil group compared with no-treatment controls. This effect was not demonstrated in the placebo group. As a pilot study, it was not sufficiently powered to find the difference between the fish oil group and the placebo group significant. Further work needs to be undertaken to conclusively demonstrate these data trends. However, the findings from this research support the literature in finding a protective or 'adaptogenic' role for omega-3 fatty acids in stress.