Pathology is the study of disease. It is sometimes very difficult to clarify the precise boundary between a state of health and a state of disease.
While health is a state of balance, disease is instead a state of imbalance. When viewed from a multi-system perspective, there is an imbalance between the contribution to disease and the deterrents to disease (diagram). This multi-system imbalance results in a pathological cascade (diagram). To understand this process, it is first necessary to understand each component of the pathological cascade. The proximate cause of disease can be viewed as an adaptive failure. It often begins with a state of extreme imbalance and is most often the result of the interaction between a vulnerability and a life circumstance. In some instances an extreme vulnerability alone or an extreme environmental circumstance alone many result in pathology.
In a state of health, there is an adaptive capacity to acquire and allocate a balanced ration of the resources needed for survival. An insufficient amount of any resource results in a deficiency, while an excess of a resource or anything else in the environment may be toxic. In a pathological state there is either a failure or a dysregulation of the capacity to acquire and allocate needed resources and to defend effectively against threats. In some instances there may be an impaired capacity to adequately discriminate between what is harmful or beneficial and/or an impaired capacity to respond with adequate adaptive specificity. This adaptive failure may be further magnified when a subsequent cascade of events causes further adaptive failure resulting in a disintegrative vicious cycle. In nature, there is a redundancy of checks and balance, which often acts as a safeguard preventing pathological processes. In addition, many weaknesses may be compensated by other stronger capabilities. Although constant change, stress, and distress are frequent events; pathology usually occurs only when there is an interaction of a vulnerability and a life situation that cannot be compensated because there is a sequence of failures of multiple regulatory systems which are often safeguards to disease.
Vulnerabilities to disease may be genetic, developmental and caused by prior trauma. There may be increased vulnerability associated with early and later life. A state of acute or chronic stress may increase vulnerability when resources are allocated to other functions. Genetic vulnerabilities must be understood in the context of evolution. Genetic vulnerabilities are far more common, while genetic defects are rare. True genetic defects which compromise adaptive functioning without any other benefit compromise reproductive success and tend to be rapidly reduced in the gene pool. Genetic defects are associated with a large number of rare conditions, but do not cause common widespread diseases, which affect large numbers of people
Genetic vulnerability to disease may be a result of the unique path of evolution or design compromises.* The unique path of evolution is determined by many unknown historical events. This has led to the development of genes, which have current adaptive value, being added to or replacing genes which had adaptive value in some prior environmental circumstance. This results in traits which may have no or little current adaptive value that are best understood from a greater understanding of the history of evolution.
Design compromises are traits, which have adaptive value in certain environmental circumstances that may compromise adaptive capacity in other life situations. A failure to appreciate this concept has results in many genetic vulnerabilities being mislabeled as genetic defects. Examples of these genes include sickle cell traits and the gene for cystic fibrosis, both of which afford some protection against infectious disease
Developmental vulnerabilities are a result of a past environmental circumstance, which caused trauma at a critical point in development. In general, trauma associated with earlier stages of development is associated with a greater adverse impact upon subsequent development. These traumatic events may include – a failure to acquire needed resources, toxic exposure and adverse consequences of infectious disease.
Trauma may often have a more severe impact upon the very young or very old than upon a mature adult. Trauma is sometimes associated with residual injury, which may cause dysregulation of adaptive functioning and contribute to increased vulnerability in the future.
Change in the allocation of resources in the body at times of stress contributes to disease in some instances. In a state of physiological stress, there is a shift in the allocation of resources which results in decreased environmental functioning and increased immune functioning (sickness behavior.) In a state of environmental stress, conversely there is a shift towards increased environmental functioning and decreased immune functioning. These changes in the allocation of resources are mediated by an interaction of the hormonal, nervous, and immune systems. Although acute stress is often well tolerated and beneficial chronic stress and/or a dysregulation of the stress response systems results in a prolonged imbalance in the allocation of resources which may contribute to increased vulnerabilities for functions which were compromised by a decreased allocation of resources.
*Nesse, Randolph. Why We Get Sick, The New Science in Darwinian Medicine, Times Books, Random House 1995.
Life situations, which contribute to disease, include lack of resources, toxic exposures, environmental extremes, and competition with other organisms.
An extreme lack of resources or toxic exposure results in obvious, and well recognized patterns of disease, while more subtle resource deficiencies and/or toxic exposure contribute to more cryptic disease syndromes. In either case, lack of resources and toxic exposure can result in increased vulnerability to other disease.
Although man has considerable flexibility adapting to environmental extremes, there are limits and extreme environments that may contribute to disease.
Some of our current pathology may be a result of our difficulty adapting to the changing environment caused by rapid technological changes. We are only a few hundred generations out of the Stone Age, a brief time from a evolutionary perspective, Although humans are highly adaptive to live in a broad range of environmental conditions, technological advances have caused a rapid change in our culture and physical environment – from the Stone Age through the Agricultural , Industrial, and now the Information Age revolutions. Although these changes have had many benefits, it has also led to a rapid environmental change resulting in changing patterns of disease.
Competition with other organism can contribute to disease and result in trauma that increases vulnerability to subsequent disease. Some of this competition is with in our own species for resources and mates. In addition we also compete with some other species, the most significant being microbes. Microbes possess a competitive advantage because they reproduce much more rapidly than humans. This difference affords microbes an opportunity to evolve adaptive capabilities faster than humans can evolve defenses. There is a never ending arms war between our defensive mechanisms and the invasive capability of pathogens*. Some disease is the result of injury from infectious disease resulting in vulnerability to other disease processes.
In most cases, specific life situations combined with specific vulnerabilities lead to disease. Although many pathways of disease exist, the final pathways are often events that overwhelm adaptive capacity and/or cause adaptive mechanisms to go awry, leading to a pathological cascade of events resulting in a pathological vicious cycle. The pathological process may evolve and persist in multiple systems simultaneously.
“The mental jail, which may be defined as the subjective experience of life without meaning, hope or love, that feels like a prison, is far more confining. Its ceiling is too low to stand tall and proud; its walls too narrow to breathe easily; its cell to short to stretch out and relax. The sentence is indeterminate. It must be deconstructed, or suicide, homicide, or severe mental illness can result. The bricks of the mental jail are usually made of guilt and shame, rage and the need for sweet revenge, depression, fear, and feelings of worthlessness……..” (Tolstoy)
In a state of mental illness, mental functioning does not reflect the life situation and does not maintain balance by facilitating an adaptive allocation of resources, which may result in the failure to experience well being, pleasure, fulfilling relationships and productive activities and the mental flexibility to adapt to change and the ability to recognize and contend with adversity.
“Brain-related diseases and injuries are estimated to exceed over half a trillion dollars a year in health care, productivity, and other economic costs.” (NIMH statistic)
The brain regulates this allocation of resources and can be conceptualized in three fundamental regions – the cerebral cortex (cognition), the limbic system (emotional functioning), and the brain stem and hypothalamus (vegetative functioning). Cognition, emotional and vegetative functioning are all interactive systems. Some pathological conditions affect all three areas, while other conditions primarily affect specific areas.
Dysfunction of the cerebral cortex is associated with an impairment discriminating beneficial from harmful aspects of the environment and/or an impairment discriminating adaptive responses and the flexibility to respond quickly to changing environmental circumstances.
Dysfunction of the limbic system is associated with emotional reactivity that does not reflect the current life situation and impedes adaptation. The current mood facilitates adaptation by altering perception, processing, vegetative functioning, and behavior. In a state of health, mood reflects the life situation and facilitates adaptation (Figure 1). When threats exist, it is adaptive to experience negative or adversive mood states. Although the predominance of adversive moods is adaptive in threatening situations, their predominance in a benign life situation impedes adaptation (Figure 2). Likewise, the predominance of a positive mood in a threatening situation is also pathological (Figure 3). An inability to adequately discriminate, shift, and experience the mood which is adaptive, resulting in failures that invariably leads to predominance of adversive mood states such as fearful obsessiveness, phobias, panic, and depression.
Dysfunction of the brain stem and hypothalamus is associated with dysfunction of the allocation of somatic resources resulting in impairments of vegetative functioning (i.e. sleeping, eating, sexual functioning, temperature control, circulation, physiological responsiveness to stress and immune function). Cognitive, emotional and vegetative functioning are all interactive systems. A dysfunctional interaction of these systems can result in pathological behavior that impairs adaptation in the current environmental situation.
Within the nervous system, psychopathology correlates with the combination of a dysfunction of neurochemistry, altered neural architecture and altered gene expression. Conversely, therapeutic intervention correlates with a normalization of neurochemistry, neural architecture, and gene expression.
It is important to make the distinction between psychiatric syndromes vs. the cause of these syndromes. For example, major depression is one of many psychiatric syndromes of dysfunction. It appears to be caused by a complex interaction of genetic and other vulnerabilities and a life situation possibly requiring a certain time sequence. In other instances, the same vulnerability on the same stressful life situation may contribute to causing totally different psychiatric syndromes, or no disease state dependency upon the impact of other contributory factors.
When there is a dysfunction of the nervous system, we can partially compensate with conscious free will. However, there are limits in our capacity to compensate for some psychic or somatic limitations and impairments. It is necessary to emphasize the difference between syndromes of dysfunction and causes of pathology. Depression shall be discussed as an example of a syndrome of dysfunction, while one significant cause of mental pathology shall be discussed in Microbes and Mental Illness.
Disease is often comorbid with other related disease entities, leading to interactive disease states. Therefore, we cannot view a disease process as a closed system. Instead, we must understand the interaction of comorbid disease processes, some of which are full syndromal and others, which are sub-syndromal. The comorbidity may be somatic/somatic, somatic/psychic, or psychic/psychic. Somatopsychic disease is caused when physical (somatic) distress causes mental (psychic) illness. Conversely, psychosomatic disease is caused when psychic distress causes somatic illness.