Towards optimal measurement and analysis of salivary cortisol
Our aim is to inform the optimal measurement and analysis of salivary cortisol in order to unpick the role of cortisol in stress, wellbeing, health and disease. We examine the diurnal cortisol rhythm and its underlying ultradian rhythm, particularly in the post-awakening period. We have demonstrated the importance of participant sampling accuracy to the saliva sampling procedure, carried out in participants’ domestic settings. We have assessed and promoted the use of objective measures (eg track caps, time-stamped photos and actigraphy) facilitating the accurate measurement of salivary cortisol. We have examined the association of other relevant hormones (eg melatonin) to understand effects on cortisol.
Recently, we have developed measures of cortisol salience (ie rapid and brief bursts of cortisol followed by deceleration of cortisol secretion), which may have additional utility in comparison to traditional composite measures of cortisol. Some of this work informed the consensus guidelines on the cortisol awakening response (CAR: the rapid rise of cortisol following morning awakening, a distinct aspect of the diurnal cortisol rhythm), which was led by Dr Tobias Stalder at the University of Siegan, in Germany.
The role of cortisol in stress, wellbeing, cognition and health
We are interested in the relationships between psychosocial variables, cognition, health and cortisol secretion in healthy and clinical populations. Notably, we have examined salivary diurnal patterns in patients suffering from chronic breathlessness receiving supportive and palliative care services, led by Dr Richella Ryan at the University of Cambridge. We have also examined the association between attachment style and cortisol stress responding, in collaboration with Dr Andrea Oskis at Middlesex University. As well as the measurement of salivary cortisol, we have investigated associations between hair cortisol and wellbeing in younger and older healthy females, in collaboration with Dr Tobias Stalder. Currently we are examining the variability of post-awakening cortisol, in terms of its salience, pulsitility and variability, in relation to health.
In studies examining the role of cortisol in cognition and balance, we have shown that the CAR and cortisol responses to stress are associated with executive function and postural sway (an indicator of balance). This work has been undertaken in collaboration with Professors Catherine Loveday and John Golding at the University of Westminster.
We are also interested in the role of cortisol in optimal brain activity and function. Using rapid transcranial magnetic stimulation (rTMS) to induce brain plasticity in the motor cortex we demonstrated that the size of the CAR predicts capacity to induce neural plasticity. Using EEG, we are currently examining the association between post-awakening cortisol secretion and neural connectivity. This work is in collaboration with Professor Mike Ridding at the University of Adelaide; Dr Brendon Hordacre at the University of South Australia; and Dr Xia Shi at the University of Technology and Education, in China.
Other research includes the role of psychological stress reactivity in prospective health outcomes, led by Dr Turner at Deakin University in Australia, and in association with the International Glaucoma Association, we are investigating whether reduced retinal sensitivity in open angled glaucoma is associated with an attenuated CAR and poor psychological wellbeing.
Strategies to manage stress and regulate cortisol and the promotion of good mental health and wellbeing
We are currently investigating the benefits of exposure to nature, physical activity and a combination of the two (known as green exercise) for health and wellbeing. We are particularly interested in their effects on the physiological stress response and the diurnal cortisol rhythm. Working with healthy and clinical populations, we have shown that exposure to nature, physical activity and green exercise are associated with healthier cortisol stress responses and/or diurnal patterns of cortisol. Some of this work is in collaboration with The Conservation Volunteers, Dr Carly Wood at the University of Essex and Professor Jenny Roe at the University of Virginia in the US. Further, in collaboration with Professor Daniel Corcos at Northwestern University in the US, we have shown that engagement in endurance exercise can reduce cortisol levels in Parkinson’s Disease patients, a group who typically exhibit high levels of cortisol.
Emeritus professor, Phil continues research associations with long-established collaborators and partners in universities abroad. At Universitat de les Illes Balears, Spain, he examines the links between diurnal cortisol decline rates and outcome measures from cognitive behavioural therapy. At Hong Kong University Phil has also served as an advisor to the Centre on Behavioral Health, a multi-disciplinary team of clinicians and academics seeking to integrate theory research and practice.
Led by Dr Jermaine Ravilier at Bath Spa University, Nina is a co-applicant on a Challenge Fund study, the HOW (Healthier Outcomes at Work) social wok project. We are working with social care trusts to develop an app-based intervention to reduce workplace stress in social workers. The project seeks to reduce sickness absenteeism by managing stress in the workplace and in turn improve health and well-being.
In collaboration with Dr Jay Mackenzie and Dr Tina Cartwright at the University of Westminster, Nina is working collaboratively on several projects in which we are developing and evaluating strategies to increase wellbeing in University students. A current project aims to support people who are providing support to another individual for self-harm (see CHERISH Support).