Mind & Body
In the treatment of physical ailments not only the elimination of pathogens plays a role. There also exists a complex communication network between the immune system and the brain via which these two main supervisory faculties of an organism influence each other. One example for this is stress and the influence of the so called HPA-axis (hypothalamus-hypophysis-adrenal cortex) on inflammatory as well as on psychological processes. Various measures for the reduction of stress (also assisted by pharmacotherapy) can contribute to recovery by supporting the body to rebalance the disturbed communication between brain/mind and immune system.
In the beginning of the twentieth century physicians and nurses attributed a high importance to the mental state of their patients. With the uprising success of synthetic substances in infection medicine, the idea that only the elimination of pathogens is important when combatting feverish and inflammatory processes took hold. The role psychological conditions play in physical disorders slowly sank into oblivion. Nowadays, insights from molecular medicine and pharmacology demonstrate the existence of a complicated communication network between immune system and brain via which these main supervisory systems of the organism continuously exchange biochemical signals. Disruptions in this communication network (inherent defects, influence of pharmaceuticals, poisoning, surgical procedures) cause or enhance certain diseases that otherwise could be prevented or dampened by the immune or the nervous system, leading to the onset of infections, inflammation, autoimmune disorders or psychological diseases.
When observing the stress response of an organism for example, the links between immune, hormone and nervous system become apparent: the decentral immune system is activated and automatically turns against pathogens, degenerated cells and extraneous molecules (“stressors”), when these threaten the homeostasis of the body. Simultaneously, an exacerbating immune response needs to be prevented in order to inhibit allergies or autoimmune reactions. In an (emotionally) threatening situation the hypothalamus – that belongs to the limbic system – transmits signals via a hormone cascade through the pituary to the adrenal cortex (corticoreleasing hormone CRH, adrenocorticotropic hormone ACTH). The adrenal cortex in turn secretes the classical stress hormones adrenaline and cortisol, to put the body into an appropriate state of alertness (increased blood-pressure, increased vigilance/fear/tension, getting ready for “fight or flight”, change of activity of sympathetic and parasympathetic nervous system, inhibition of currently unimportant processes like digestion, sleep or sexuality). At the same time, the steroid hormone cortisol acts as a strong immune regulator and inhibitor of inflammation and influences a large number of metabolic functions. Furthermore, it could be shown that chronic stress also leads to down-regulation or loss of cannabinoid type 1 (CB1) receptors in various regions of the brain.
Cortisol inhibits the hypothalamus in a feedback loop, thereby inhibiting the hormone cascade that would induce the secretion of more cortisol. In contrast, cytokines secreted by immune cells indirectly stimulate either indirectly via peripheral nervous fibers or also directly the hypothalamus, and hence the HPA-stress-axis (hypothalamus-pituary-adrenal cortex). The hypothalamus is also regulated by superior brain structures like the neocortex (higher personality factulties).
Fig 1-2. Wellbeing and health depend on the balanced interaction between body and psyche. Stress- and immune system can both stimulate (red arrows) and inhibit (blue arrows) the activity of each other; adapted from: Biopsychologie, Spektrum Academic Publisher
When this finely tuned regulation is disturbed in one or more positions, further diseases can result: atypical depression and other diseases that go along with fatigue and increased appetite (i.e. fibromyalgia, early stage rheumatoid arthritis), often correlate with a hypo-active hormonal stress axis and simultaneous overactive immune system, that manifests in joint or muscle pain, allergic symptoms or increased antibody titers in the blood. In contrast, the classical depression is characterized by a structured state of fear in patients that could be described as “fear-biased physiological overexcitation / chronical activation of the stress axis”. This condition usually comes with sleeping problems and lack of appetite on the one hand and with a diminished immune function on the other hand; this may facilitate the development and progression of degenerative diseases and cancer on the long run.
The discovery of the intertwinement of neuronal stress responses and the immune system might explain the clinically observable comorbidity of e.g. arthritis and depression. There is reason to suspect that the nature of the disruptive stimulus (pro-inflammatory or psychologically challenging) determines which of the symptom complexes dominate. Thus, the scientific findings confirm anecdotal experience that psychologically challenging situations enhance inflammatory disorders and susceptibility to infections; conversely, positive life circumstances improve the patient´s physical state.
It is possible to utilise this effect, for example by reducing stress through physical activity or by implementing a mental practice that improves stress susceptibility, evidently balances the stress axis and increase stimulus thresholds (e.g. meditation, mindfulness practice). A network of safe and supporting social relationships – also in the context of a group therapy – also dampens the susceptibility to stress and strengthens the immune system. In case of chronic disease, a stay at a health resort can be helpful to recalibrate the disturbed communication between brain/mind and immune system/body by complete tranquility and absence from everyday life. Correctly-regulated immune responses are the first requirement for physical recovery, even though one can support beneficial endogenous processes with pharmaceuticals. All in all a strict distinction between psychological and organic diseases is an outdated medical concept. Psychoneuroimmunology proves that body and mind are closely intertwined.
Challenge strengthens, challenge toughens. This is true for the body as well as for the mind. A constantly spared immune system is incapable to learn the correctly orchestrated defense against pathogens. Similarly, an individual who never experiences setbacks and never learns to overcome crises, sometimes with professional help, is not able to develop his personality and to mature psychologically.
Biopsychologie, Kapitel: Psyche, Stress und Krankheitsabwehr; Spektrum Akademischer Verlag, ISBN-10: 3827402190, ISBN-13: 978-3827402196
Morena M, Patel S, Bains JS, Hill MN. Neurobiological Interactions Between Stress and the Endocannabinoid System. Neuropsychopharmacology. 2016;41(1):80-102. doi:10.1038/npp.2015.166
McPartland JM, Guy GW, Di Marzo V. Care and Feeding of the Endocannabinoid System: A Systematic Review of Potential Clinical Interventions that Upregulate the Endocannabinoid System. Romanovsky AA, ed. PLoS One. 2014;9(3):e89566. doi:10.1371/journal.pone.0089566