How can cortisol measures inform us on the effects of mindfulness on stress?

Discuss the challenges and pitfalls involved in the use of cortisol measures by scientific studies, as well as the evidence implicating these measures in the context of meditation practice.

Mindfulness is a therapeutic set of principles and methods, with a strong evidence base for its efficacy. Its foundations were inspired by age old Buddhist techniques and concepts, modified for contemporary secular practice and backed by scientific research and development. In relatively recent years, it has achieved widespread mainstream adoption, with applications including treatment of affective disorders, stress and pain reduction as well as improving wellbeing and productivity in the workplace.

Stress is an adaptive response to potentially threatening environmental conditions. As an adverse environmental stimulus is perceived, specific neurological and biochemical signal cascades are activated, which alters psychophysiology to a confer survival advantage.

Cortisol is one of the main hormones involved in the stress response and a key biomarker for stress measurement. However, the correlation is far from linear, with a myriad of factors affecting the interaction between the two. These range from the time of day and method of cortisol extraction, to subjective and physiological disparities. Making the reliability of cortisol measurements as a stress indicator somewhat precarious.

Cortisol levels naturally fluctuate alongside the body’s circadian rhythms, with an initial peak occurring in the first 30-45 minutes after waking up (Pruessner et al. 1999). This cortisol awakening response (CAR) is an important indicator for healthy endocrine function, with adults showing significantly more consistent CAR from day to day and a sharper rise than children (Bernsdorf & Schwabe 2018).

Hypothalamic Pituitary Axis dysfunction can cause cortisol levels to become elevated or diminished, giving rise to hypercortisolism and hypocortisolism respectively. An increase in stress perception also changes the pattern of cortisol levels with less pronounced peaks but an overall higher diurnal concentration (O’Connor et al. 2009). Distorted reactions arising from cognitive maladaptation toward stress inducing stimuli, causes an increase in cortisol secretion. This in turn contributes to a vicious cycle, which facilitates adverse memory recollection and associated emotions as well as reinforcing reaction habituation towards homologous stimuli (Hannibal, K. E., & Bishop, M. D. 2014).

Mindfulness interventions can intercept and reduce the stress response at the level of perception to reduce reactive habituation. This diminishes HPA axis activation, which attenuates the stress response and curtails the associated vicious cycle that leads to chronic elevated cortisol and stress (Sanada et al, 2016). The large RCT meta-analysis carried out by Sanada et al. (2016), also suggests that the reduction in cortisol levels is influenced by the number of hours and sessions dedicated to Mindfulness practice as well as the age of test subjects. Furthermore, this study strongly emphasizes the importance of a consistent cortisol extraction method, applying rigid methodologies of MBSR or MBCT and ensuring quality control with active control groups.

As blood cortisol concentrations rise, saliva concentrations do not increase proportionately. Rather they remain relatively low until the blood is saturated, at which point the saliva concentration rapidly spikes. Blood cortisol is more accurate than salivary cortisol for assessing stress as its levels are relatively consistent throughout the day. However, being an invasive method by way of utilizing a syringe adds a stress factor, causing potential false positive results. Salivary cortisol levels are highly volatile by comparison, but this method has the advantages of being stress free and self-administrable (O’Leary et al, 2016).

Hair cortisol is another stress-free source for consideration. Hair grows approximately 1cm per month and remains test worthy for long periods of time due to inherent resistance to degradation unlike blood, saliva and urine. However, it is useless for detecting short term cortisol fluctuations generated from acute stressors and variability in growth rates occur relative to age and ethnicity (Gow et al. 2009). As such, hair cortisol can provide a reliable long-term comparative indication of the benefits of MBI’s on stress but could not distinguish diurnal fluctuations nor flattening of peak cortisol spikes caused by maladaptive reaction habituation, which mindfulness is proven to attenuate.

A study by Chadi et al. (2016) on chronic pain, utilized a broad repertoire of different MBI’s practiced in succession over eight weeks. The evidence showed that salivary cortisol levels and pain reduced over time, however no other psychological improvements predicted from such a comprehensive mindfulness-based approach were observed. This was attributed to the small test group size.

A drawback of cortisol as indicator of stress levels is the significant inconsistency across extraction methods and a poor approximation to an individual’s perceived level of stress. However, the fact that cortisol levels are considerably reduced following the completion of a mindfulness-based intervention course signify the potential benefits of mindfulness practice. Furthermore, the studies so far appear to be limited by rather small test group sizes, lack of randomized control trials and diversity of subjects.

 

 

Pruessner, J. C., Hellhammer, D., & Kirschbaum, C. (1999). Burnout, perceived stress, and cortisol responses to awakening. Psychosomatic Medicine, 61, 197–204.

Bernsdorf M, Schwabe L. Cortisol response to awakening in prepubertal children and adults: Magnitude and variability. Psychophysiology. 2018;55:e13273

Hannibal, K. E., & Bishop, M. D. (2014). Chronic stress, cortisol dysfunction, and pain: a psychoneuroendocrine rationale for stress management in pain rehabilitation. Physical therapy, 94(12), 1816–1825. https://doi.org/10.2522/ptj.20130597)

O’Connor, D. B., Hendrickx, H., Dadd, T., Elliman, T. D., Willis, T. A., Talbot, D., … & Dye, L. (2009). Cortisol awakening rise in middle-aged women in relation to psychological stress. Psychoneuroendocrinology, 34(10), 1486-1494.

Sanada K, Montero-Marin J, Alda Díez M, Salas-Valero M, Pérez-Yus MC, Morillo H, Demarzo MMP, García-Toro M and García-Campayo J (2016) Effects of Mindfulness-Based Interventions on Salivary Cortisol in Healthy Adults: A Meta-Analytical Review. Front. Physiol. 7:471. doi: 10.3389/fphys.2016.00471

Gow R., Thomson S., Rieder M., Van Uum S., Koren G. (2010). An assessment of cortisol analysis in hair and its clinical applications. Forensic Science International, 196, 32–37. 10.1016/j.forsciint.2009.12.040

O’Leary, K., O’Neill, S., & Dockray, S. (2016). A systematic review of the effects of mindfulness interventions on cortisol. Journal of Health Psychology, 21(9), 2108-2121