Although their derivations were in different millennia, the modern biomedical models of allostasis/allostatic load and the EMS share striking similarities with the ancient paradigm of TCM. Their convergence conceptualizes a possible explanation for the genesis of many of the functional somatic syndromes that currently confound and defy conventional approaches.
Unlike conventional medicine's emphasis on physical stressors, the allostatic load model places equal emphasis on the significance of emotional and mental stressors as having serious detrimental effects on the body. The TCM observation that psychological stressors lead to physical symptoms and vice versa can be modernized through allostasis/allostatic load and the EMS. They not only describe the physiological output resulting from emotional stressors but also describe a modifiable gain system affected by physiological input from the periphery.
Both stress the fundamental importance of homeostasis in the body. In fact, in modern Western and TCM paradigms, the basic goal in maintaining health is preservation of balance, described in each paradigm as homeostasis or balance of yin and yang, respectively. In the process of allostasis, the organism invokes physiological changes mediated by broadly acting regulatory systems in response to a stressor that threatens (or is perceived as threatening) homeostasis. The TCM theory of yin and yang describes this same phenomenon. However, instead of referring to the mediators of homeostatic regulation as glucocorticoids, serotonin or catecholamines, TCM mediators are described by terminology such as qi, blood and essence.
Both models allow for a period during which an individual is able to accommodate for stressors. The breakdown of homeostasis involves several factors. One key factor is an individual's underlying constitution. Allostasis describes inherited genetic traits and early life events as conferring stress resilience to an individual. In TCM, this is referred to as a person's jing
). These references to a person's innate reserve explain the common clinical experience that individuals differ in stress adaptabilities and susceptibilities. Regarding functional somatic syndromes, this underlying vulnerability accounts for individual tendencies to develop adverse outcomes from stressors that most individuals are otherwise able to tolerate.
In conjunction with an individual's underlying constitution, the breakdown of homeostasis results from chronic, sustained stress, with or without punctuation by a severe, acute stressor. Patients with functional somatic syndromes often convey a long history of repeated life stressors during which most symptoms are self-limiting or relatively quiescent. This may represent initial adaptive responses of homeostatic mechanisms. However, either after an acutely stressful event or after several years of stressors, symptoms seem to suddenly arise and persist thereafter. This is consistent with both models in which, after a critical degree of stress, compensatory mechanisms are overloaded and thereafter fail to function optimally, ultimately leading to symptoms. In this way, the concept of allostatic load can be considered similar to the patterns of dysregulation in TCM.
Rather than affecting only one peripheral target, both ancient and modern models purport that pathological stressors systemically disturb the mind-brain-body continuum. (A pathological stressor, in this context, refers to a perturbation that is severe or sustained enough to result in allostatic load.) In TCM, stressors induce imbalances leading to an underlying pattern of dysregulation which manifest with multisystemic symptomatology. Within the model of allostatic load, stressors affect broadly acting regulating mechanisms, resulting in a similar multisystemic presentation. This conceptualization better explains why the majority of patients with functional somatic syndromes, regardless of the specific disorder for which they seek medical care, will present symptoms from multiple systems. Further, many present complex symptoms such as fatigue, lethargy, low resilience, sleep disturbance and mood disturbance, which are difficult to explain by a specific organ dysfunction. These systemic symptoms are easily explained by a complex interplay of alterations in ascending monoaminergic systems (e.g., depletion of serotoninergic mechanisms and upregulation of noradrenergic systems), tonic and phasic alterations of autonomic nervous system activity (e.g., low cardiovagal tone, increased sympathetic nervous system reactivity), alterations in HPA axis tone and responsiveness and tonic and phasic pain modulation systems (38
As intriguing as the comparison between the ancient TCM paradigm and the emerging modern neurobiological models may be, they are simply comparisons at this point. The similarities are most striking in the TCM pattern diagnosis, where specific somatic patterns are associated with specific alterations of emotions. Other aspects of the TCM paradigm, such as the concept of qi and the meridians, have not been addressed in our discussion and may be more difficult to address from a Western scientific perspective. Finally, the apparent similarities between TCM pattern classification and distinct mind-brain-body states will need to be verified in future hypothesis-driven mechanistic studies.
The correlations between TCM, allostasis/allostatic load and EMS models offer exciting opportunities to scientifically test novel theories on the pathogenesis of the functional somatic syndromes and to investigate biomedical explanations underlying ancient TCM terms and concepts. For example, in the case of IBS, current diagnosis under the Rome criteria focuses solely on bowel symptoms (42
). However, in clinical practice most IBS patients present significant extra-intestinal symptomatology. In fact, clinical evidence suggests that normalization of bowel habits alone by anti-diarrheals or pro-motility drugs is unlikely to produce large improvements in global endpoints when compared to placebo (33
Further, the present group has demonstrated that both mental and physical component scores for HRQoL in IBS are primarily determined by extra-intestinal symptoms rather than conventionally-elicited bowel symptoms (29
). Rather than conventionally subgrouping IBS patients on the basis of bowel habits alone (e.g., constipation- versus diarrhea-predominant), TCM broadly subgroups patients into deficiency (i.e., yin
) or excess (i.e., yang
) types based on extra-intestinal symptoms such as fatigue versus hyperactivity or weak stress resilience versus stress-induced overstimulation. The present group has hypothesized that this TCM approach potentially offers novel and scientifically testable subgroups of IBS representing differential dysfunction (i.e., hypofunctioning in yin
types and hyper-responsiveness in yang
types) of allostasis and EMS output profiles. Specifically, we have begun preliminary physiological studies comparing basal and stress-induced autonomic differences in IBS patients to determine if our hypothesis is supported. We believe integrative East–West approaches such as this represent a sound first step towards scientifically validating the ancient theories of TCM while throwing light on central physiological derangements underlying the functional somatic syndromes.