The relationship between stress and disease

I first notice my heart-rate quicken, then I spot my breath is short but rapid, and localised to my upper chest. My awareness then switches to my mind, and I feel panic and I’m unable to concentrate on anything else. I know this feeling all too well: “stress”.

These are just some physiological and psychological symptoms of the body and mind responding to external stressors which result in ‘The Stress Response’. With the Sympathetic Nervous System (SNS), a strand of the Autonomic Nervous System (ANS), in full swing, my body is preparing itself to ‘fight or take flight’.

I’ve described my physiological experience of stress first, as my afferent sensory input e.g. breath, has dictated my psychological response (efferent) which in turn has influenced my biological response (two-way feedback loop). Or from the perspective of the Koshas (sheaths): Anamaya Kosha and Manas connection, with additional input from Pranamaya Kosha, has influenced Manomaya Kosha and vice versa i.e. body-mind / mind-body connection.

If I were being chased by a giant bear, then this mind-body reaction would be very beneficial for survival. However, I’m not being chased by a giant bear, instead I’m responding, like everyone else, to every-day life stressors. This begs the question; what effect is all this over-active stress having on my body and mental health?

In recent years, the medical world has accepted the relationship of stress as an aggravator of disease – for example experts such as H. Benson M.D. claim “60-90% of visits to doctors are in the mind-body, stress-related realm poorly treated by any drugs or surgery”[1]. As a result, Doctors now prescribe lifestyle changes and encourage stress-reducing activities. For the Yogic tradition, the mind-body concept isn’t a new one, and references can be found as far back as the ancient (Katha) Upanishad BCE.

The starting point for stress is the Hypothalamus (although this isn’t the only part of the brain activating the stress response) as this brain region regulates the ANS, the Endocrine System (ES) and the Immune System which all work in unison. With sensory neural input (from the Peripheral Nervous System) directing the Hypothalamus to induce ‘The Stress Response’ both neurally, SNS ramped up, and hormonally, ES activity increases.

From a neural perspective the fast-acting SNS excites the body (by invoking the adrenal glands to release the neurotransmitters norepinephrine and epinephrine) ready for mobilisation, preparing the body for ‘Fight or Flight’. Alongside the symptoms I described earlier (heart rate, breath rate increases etc.), the SNS also increases blood pressure, and if this pressure becomes habitually high there’s strong links to heart disease (e.g. atherosclerosis). Chronic stimulation of this system depletes the body’s resources, damaging lymphatic tissue and inhibiting white blood cell (T-cell) production required for immunity. Additionally, psychologically the SNS instigates feelings of fear and panic.

From a hormonal perspective, the adrenal glands release Cortisol, ‘the stress hormone’, which ramps up glucose secretion for energy (overriding epinephrine). This slower-acting process starts in the Hypothalamus and ends in the Adrenal cortex, with messages travelling via the Pituitary gland and is known as the Hypothalamus-Pituitary-Adrenal axis (HPA axis). Additionally, fewer cortisol receptors on the Hippocampus (which coordinates the inhibition of the HPA axis), either due to genetics or repeated activation of the stress hormone, means we have poorer control of the HPA axis and it takes longer to inhibit the stress response, which has negative side effects on our health.

If these hormones aren’t metabolised, say via a strong asana practice, then it manifests as emotional stress (e.g. Anxiety). Cortisol also suppresses the inflammatory response which is required for innate and acquired immunity, in turn suppressing the immune system. Similarly, Cortisol reduces Melatonin (hormone) production which is required for sleep, our main ‘state’ for healing to occur. Melatonin also inhibits tumour growth, suggesting a direct link between stress and cancer.

These manifestations demonstrate a psycho-physiological network of stress which is always coordinating with and suppressing the immune system. Alongside these biological manifestations, we also have to consider the negative impact of behavioral stress, e.g. poor-sleep, unhealthy diet, smoking etc. and how they can lead to a dysregulated immune system, which if left untreated, will culminate in disease.

We can utilize yogic breathing techniques and asana, as well as mindfulness, to regulate stress patterns and induce balance (homeostasis) within the body and mind (via neuroplasticity). One example is utilizing Mindfulness practice to induce the ‘The Relaxation Response’, known physiologically as dominance of the Parasympathetic Nervous System, allowing the body to rest and digest. A second example is how we can utilize the Koshas for self-efficacy. Firstly, physical manifestations of stress within Anamaya Kosha, delving into Pranamaya Kosha we can observe unhealthy breath patterns/pranic imbalance, and having awareness of our habits and discerning when to regulate and when to passively accept i.e. Vijnanamaya Kosha.

A certain level of stress is necessary for transformation, and we should strive to find the balance between ‘healthy stress’, and regulation of ‘unhealthy stress’ patterns. Once we have started to build resilience, and found a pathway to stability under change (Allostasis) then our physical and mental wellbeing will improve, in turn shaping longer-term health and disease prevention.

[1] Quote from Interview with Herbert Benson, M.D. ‘Health Insights Today’ publication, 2008.