Integrated-Systems Model of Stress: Framework, Tenets, Assumptions, and Predictions
- The model reflects a qualitative framework for the multi-directional connections between the 6 major regulatory systems of the body: central nervous system (CNS), autonomic nervous system (ANS), gut/immune system, endocrine system, including classifying the environment and genetics/epigenetics as individual systems. As shown, stress in any one system may not only manifest in patterns common to that particular system but may also influence other systems’ stress patterns. For example, a stressed central nervous system reflecting a pattern of depression may impact the endocrine system, facilitating a pattern of thyroid dysfunction. It is also possible for a particular clinical pattern to overlap more than one system. For example, diabetes could be considered both an endocrine and immune system pattern. Asymmetrical and Bilateral postural extension patterns (refer to PRI for more information) also overlap between CNS and ANS expressions of stress.
- There are a multitude of pathways connecting the regulatory systems. Some examples include the Vagovagal Reflex, Cholinergic Anti-inflammatory Pathway, and Microbiome-Gut-CNS-ANS, SA (Sympathetic-Adrenal), HPA (Hypothalamic-Pituitary-Adrenal, HPT (Hypothalamic-Pituitary-Thyroid), and HPGL (Hypothalamic-Pituitary-Gonadal-Liver) axes.
- The integration of each of these systems influences net allostasis. Allostasis is defined as a desirable balance in the body that reflects the ability to function with variability and flexibility. The body’s inherent purpose is to survive under pressures of natural selection which involves the ability to adapt while efficiently utilizing energy under competing and cooperating systems. Allostatic balance is the goal of system integration. When any one of these systems is under stress, various patterns, behaviors, and adaptations may emerge, as outlined in the model. For example, a stressed central nervous system may symptomatically present as a psychological issue (anxiety, depression) or as pain. However, it may equally present as a visual dysfunction (astigmatism, myopia, etc.), a less commonly regarded stress pattern of the central nervous system. Any one stress, regardless of the way in which it is manifested, may ultimately create allostatic imbalance.
- Allostasis and homeostasis are different. Homeostasis is the short term and immediate physiological regulation of essential bodily functions such as ph, oxygen level, and body temperature. Without maintenance of these sets points, death may occur. Homeostatic set points keep the body alive. Allostasis is the long term physiological regulation of homeostatic functions via systems integration, as outlined by the model.
- When the body perceives a stressor, or threat, it can react in a variety of ways and manifest in any of the potential patterns or adaptations, as outlined by the model. Particular stressors may be processed differently by individuals. Ultimately, it is the individual’s perception of threat and the body’s resulting prioritization of resources that leads to a particular stress pattern/response. For example, while the task of completing a challenging work project may be interpreted as invigorating to one individual, it may prove overwhelming to another. The two individuals in this example respond differently to the same “stressor”. They perceive and process the “stressor” according to their own unique patterns of systems integration and baseline allostatic set points.
- The perception of threat is not always reality. Human consciousness, with its interplay between emotions and cognition, serves an important function of predicting and interpreting our environment for efficient function. However, this amazingly complex and powerful ability can also cause unintended stress for us when we form maladaptive perceptual patterns. For example, one’s perception that they must complete all of their work tasks perfectly in order to succeed results in a constant state of vigilance; realistically, however, it may not be necessary to perform at such an intense level in order to succeed.
- The model does not provide quantitative relationships between the various systems. It simply recognizes that altered stress in one system has the potential, however small or large, to influence any other system. Furthermore, this influence may manifest as a reactionary increase, decrease, or no change in stress to any other system. Typically, we would assume that decreased stress in any one system would result in decreased stress in others, giving a net reduction of total system stress and an improved allostatic balance. However, this may not always be the case, as it is possible to have opposing stress reactions. For example, a classically trained dancer who has made beneficial neuromuscular changes to her posture (decreased stress) may become psychologically distressed given that the new posture she has adopted is contrary to her years of training.
- Balanced allostasis between all the systems not only requires periodic exposure but also graded exposure to “healthy stress.” This is referred to as hormesis. Properly-dosed exercise (physical learning) and mental stimulation (cognitive learning) are such examples of “healthy stresses”. The body must evolve periodically via mental and physical challenge in order to maintain its ability to function with variability and flexibility in a balanced manner. Disruption of allostasis and subsequent stress patterns may emerge when any one or multiple systems are chronically or excessively challenged.
- Changes made to any one system may temporarily result in a period of generalized instability, as the network of systems adapts and re-stabilizes around a new-found reference point of allostasis. The question becomes whether a particular system or even the network of systems will re-stabilize in a positive manner with the intended changes, revert back to the initial status, or result in an undesirable change. For example, PRI Vision intervention involves the use of lenses as a stimulus to “neutralize” the neuromuscular system and facilitate more efficient and functional postural patterns. Because of the profound influence the visual system has on the neuromuscular system, such a stimulus has the potential to create significant disequilibrium. The amount, type, and location of any one interventional stimulus applied to the system must be considered carefully, in an effort to best manage any potential temporary instability and direct the system to reaching a new beneficial state. Once a system has re-stabilized to the desired goal, consideration must be made as to how to maintain this state or better yet, continue to improve it. This brings us back to the concept of hormesis, defined above as the need for periodic properly-dosed stress stimuli.
- Sometimes it may be necessary to prioritize system interventions in order to achieve a desirable individual system or allostatic change. For example, a patient seeking therapy for postural imbalances but who also presents with an over-active immune system, with accompanying increased systemic inflammation, may not be able to progress with a neuromuscular training program until the immune system is properly addressed.
- The desirable level of stress in any one system will be influenced by the demands on that system. There may be a discrepancy between what is actually best from a balanced allostatic standpoint than from a functional one. For example, an elite-level athlete or active soldier may need to function at a higher stress level in order to successfully complete their goal-oriented tasks. Individual system needs must be considered.
- The model, as shown, acknowledges the asymmetrical and lateralized nature of the human body and depicts a need for alternation within each system. The amount and degree of alternation may be variable based on that specific system’s and individual’s functional needs.
- Imbalance of any of the systems and their related pathways and mediators will likely occur before the onset of actual pathophysiology. The former may be referred to as an allostatic state with examples being hypertension, excessive glucocorticoid production, and/or elevated levels of cytokines. Prolonged allostatic states may result in allostatic loads such as atherosclerosis or osteoarthritis. This brings up the question of “At what level should healthcare intervene at redirecting and correcting dysfunctional states and pathways?”
Implications for Improving the Future of Healthcare
- Medicine has become increasingly specialized. While we do indeed need highly-skilled clinical expertise for creating successful changes to individual systems, it is important to consider the potential impact a specific intervention may have on other systems and total allostasis. The Integrative Systems Model of Stress, as outlined, provides the healthcare industry a framework from which to view and approach therapeutic intervention, highlighting stress as the main currency of allostatic balance.
- Healthcare today typically places more emphasis on intervening when a system has reached a state of pathophysiology, or allostatic load. Treatment is then traditionally directed at attenuating the symptoms vs. addressing the underlying systemic imbalances. The Model provides insight into the multi-factorial aspects of disease/dysfunction, and in so doing, reflects points of intervention that may not have previously been considered. For example, in the case of osteoarthritis, treatment will usually involve some sort of anti-inflammatory medication and perhaps even surgery if “conservative care” such as Physical Therapy is not effective. A more allostatic and integrative approach to management would be to consider what the current state of this individual’s allostatic pathways and mediators are (glucocorticoids, catecholamines, insulin, cytokines, vagal tone) and which particular system(s) intervention would be most efficient and effective. Such an integrative clinical picture might involve screening for psychological stressors or history of trauma, a comprehensive head-to-foot postural assessment, dietary analysis, and consideration of environmental toxins and stressors.
- Not only is it recommended that our healthcare system screen and intervene in such a manner as described above for situations of allostatic load but also for allostatic states where pathophysiology has not yet manifested. That is why identification of reliable and valid measures of allostatic imbalance, such as levels of glucocorticoids, catecholamines, insulin function, cytokines, vagal tone, and even postural patterns may be so valuable. Consistent assessment of risk factors for allostatic imbalances such as the status of one’s social support system and relationships may also serve as a valuable indicators of future health problems. It is recommended that the standard yearly physical include assessment of these parameters. Further research is required to create more quantitative standards for measuring allostatic states and risks.
- The Model recognizes: (a) the existence of dynamic alternating shifts within and amongst systems and b) the inherent lateralization of the mind and body. Proper rhythms between the left and right side of the body are essential for allostatic balance. These are likely novel concepts to many healthcare providers.
Incorporating the PRI Approach into an Integrative Allostatic Systems Model
- As shown in the model, asymmetrical and bilateral postural extension patterns (as described via the Postural Restoration Institute) and a lack of lateralized alternation in the neuromuscular system are possible manifestations of a stressed CNS and/or ANS. By virtue of the integrative systems model, therefore, any source of stress within the network of systems may manifest in these bilateral and/or unilateral postural extension patterns. Likewise, it may be possible to influence these patterns by addressing other systemic sources of stress. Furthermore, other patterns of stress in the body may be altered by specifically treating these postural patterns. There is a multi-directional relationship between neuromuscular expressions of stress and stress patterns exhibited by other systems.
- Healthcare practitioners must continually assess for the primary driver (s) of any given patient’s clinical presentation and consider additional referral sources (ex-Psych, Endocrine, Nutrition, Optometrist, Dentist, etc.) for proper management of the patient’s entire system. Prioritization of system intervention may also be imperative to reach therapeutic goals.
- Patients often seek out healthcare practitioners in order to address symptomatic pain. There are multiple systemic sources of pain. The most commonly regarded origin of pain is classified as being nocioceptive. Due to inefficient biomechanics and alignment, certain tissues in the body may be placed under excessive stress and strain resulting in a nociceptive pain response. Peripheral neuropathic pain is that which is based within the peripheral nervous system. Like nociceptive pain, it can also be triggered by faulty biomechanics and subsequent mechanical tensile or compressive forces. The central nervous system (CNS), itself, can drive pain via central sensitization and cortical plasticity changes. In this situation, co-activation of the autonomic, endocrine, and immune systems typically occurs, effectually perpetuating the pain pattern. Lastly, pain can be mediated by the immune system; inflammation (local and/or systemic) is a major stimulus to pain perception. On a practical and clinical level, all of the above-described pain pathways are activated and interacting to some degree within each patient’s presentation of pain. Interventions aimed at creating postural neutrality and variability can directly, as well as indirectly, influence these pain pathways. Likewise, addressing the systems that drive or mediate these pain pathways can influence inefficient postural patterns in addition to relieving the patient’s primary complaint of pain.
- CNS-mediated Pain
- Pain Neuroscience Education-Refer to The Sensitive Nervous System by David Butler and Explain Pain by David Butler and Lorimer Moseley.
- Graded Motor Imagery (Recognise, Visualization, Mirror Therapy)-Refer to The Graded Motor Imagery Handbook by Moseley, Butler, Beames, and Giles.
- Open Focus Techniques-Refer to The Open Focus Brain by Les Fehmi
- Stress Management Education
- Behavioral/Psychological Referral
- Immune-mediated Pain
- Nutritional Education
- Interventions designed for increasing vagus N. tone. The vagus nerve is primarily responsible for inhibiting inflammation and mediating the immune response. The following pathways rely on proper vagus nerve function and integration: Cholinergic Anti-inflammatory, Vagovagal, and Microbiome-Gut-CNS-ANS. The contribution of immune and CNS-mediated pain to asymmetrical and/or bilateral postural extension patterns can be addressed via additional types of intervention. Many healthcare practitioners are capable of performing these particular interventions provided it is within their scope of practice.
- CNS-mediated Pain
Questions for Further Study
- While objective testing for asymmetrical and bilateral postural extension patterns is a direct measure of neuromuscular stress, it is plausible that it may also be an effective indirect measure of systemic allostatic stress. Therefore, what is the sensitivity of PRI testing to allostatic states and loads?
- Are there other methods that Healthcare practitioners can easily use to also delineate allostasis?
- Heart rate variability, as a measure of vagal tone?
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