Psychological and neuroscientific research into stress and human stress responses is extensive, although progress in understanding its chemical formation in the brain has really only happened in the last thirty years or so. It is an important field of scientific research since it spans from distress in normal everyday life to more extreme manifestations of stress in mental disorders such as depression and schizophrenia. Stress touches most every child and adult’s life. Traumatic stress rises in the events and contexts of war, abuse, assault, rape, childhood loss, or car accidents, to name just a few. Often such events lead to posttraumatic stress disorder (PTSD), which is a pervasive form of chronic illness. Although these events occur with surprising frequency, people who do not experience trauma directly are still touched as much by just the thought of them. For example, people are exposed to such events through the news. This tends to heighten their sense of danger or threat and to increase a sense of personal insecurity and worry. Other factors such as poverty, illness, work pressure, and difficult life conditions also create stressors for the human brain and body. These are sometimes felt as chronic and persistent. This paper will use contemporary sources of research and scientific models to discuss the neuropsychological basis for stress and the effects of the brain’s stress response on a person’s thoughts and emotions. While its focus will be on chronic stress, PTSD is considered as well since it is an important original source for the development of chronic stress.
The widespread use of the term “stress” in psychology gained currency with Hans Selye’s book The Stress of Life (1956). In it he formulated a biologically-based understanding of stress. He focused on the body’s general adaptation to a challenging stimulus through a syndrome of bodily changes. Here one sees the initial start of thinking about stressors that both directly harm the person (physically) and put the body out of harmony because of any perceived psychological fear of harm. Later research shifted the emphasis away from pure biological reflex toward how environmental stimuli are perceived cognitively and reacted to emotionally. In other words, stressfulness came to be viewed not just as the brain’s static chemical or metabolic response to an event, but as a dynamic and alterable part of the interaction between a person’s mental functioning, past social experience, and the environmental conditions of the challenging stimulus itself. This led to the contemporary research models that investigate not just the effects of stress but the environments that cause stress.
The physical effects of stress on the brain are quite evident. The brain’s stress response originates in the hypothalamus, which is located at the top part of the brain stem and is responsible for a number of regulatory functions linked, for example, with body temperature and the dispersal of hormones into the blood stream. The hypothalamus has a dynamic relationship with the pituitary gland that controls the human endocrine system and the adrenal glands which secrete adrenaline. Both of these are extremely important in maintaining the body’s hormonal balance and preventing bodily deterioration or disease. They are vital to the body’s fight-or-flight mechanism of self-preservation. Stress reactions arise from the hypothalamus as natural physiological responses to stressful physical, psychological, or social situations. The physical stressors such as those that enact a fight-or-flight mechanism are temporary and involve sudden increases in glucose and adrenalin for energy (Wallenstein, 2003, p. 45).
It has been determined, however, that more long lasting physical effects occur with psychological stress as a result of prolonged or excessive exposure to stress hormones. The release of hormones like cortisol, norepinephrine, and adrenaline, if excessive due to excessive lengths of stressful situations, can have negative consequences on bodily organs. Chronic stress can increase the stomach’s proneness to ulcers, increase risk of heart disease, diabetes and asthma, impair the immune system, and accelerate artherosclerosis, among other harmful physical effects that have been studied and documented (Bremner, 2002, pp. 6-9). Without question, research continues to show that stress has effects strongly correlated with a decline in physical health and with a heightened susceptibility to negative symptoms.
Chronic or traumatic psychological stress can also cause physiological changes in the body as an adaptation mechanism. For example, researchers at Emory University discovered that childhood abuse created lasting alterations in physiological response to subsequent stress (Heim et al., 2000). This means that in traumatized people, stress reactions are heightened or exaggerated afterwards. Over time, these changes can create an exaggerated response to other stressors, can decrease the functioning of the immune system, and may lead to a higher proneness toward mood and anxiety disorders (Wallenstein, 2003, p. 55). In other words, stress can create a life-long physiological change in and impairment of brain and body functioning. Such recent findings suggest that victims of stress may in fact suffer from a neurological disorder rather than just from a character flaw, mental weakness, or pitiable bad luck.
Chronic stress can impact individual perception and thinking in significant ways. Research in cognitive neuropsychology has been particularly helpful in identifying some of these patterns. Psychiatrists at the Dartmouth Medical School have identified certain common styles of thinking present in those who as a result of traumatic stress suffer from chronic life stress (Mueser, Rosenberg, and Rosenberg, 2009, pp. 99-120). These thought patterns, or schemas, shape the individual’s perception of the world and have a large degree of negative control over their emotions. The problem with them is that they are inaccurate and destructive thoughts and beliefs. They exacerbate distress rather than alleviate it. For example, such stress-influenced minds have a tendency to catastrophize (worst case scenario), overgeneralize the negative by jumping to conclusions, and think in terms of extremes and absolutes (“the world is all bad” or “I’m a failure since I’m not perfect”). They also overestimate the risk of bad things happening, attribute truth to their feelings (“I feel sad, so my life must be hopeless”), inaccurately blame themselves when they are not responsible for something, and ignore the positive by focusing strictly on the negative. The person suffering from this kind of stress, therefore, is in the grip of false perceptions and their resulting negative emotions. Their ability to manage life experience in a non-distressful way is impaired unless they are able to find ways to change their beliefs and interpretations of the world and of themselves.
Stress has been linked to more serious impairments such as posttraumatic stress disorder, depression, somatic disorders, anxiety disorders, and substance abuse. Bremner (2002) has argued based on research that these disorders may be considered in relationship to a “common stress-induced neurological deficit” (p. 34). That is to say, stress actually changes the way the brain operates. In even more extreme cases, studies have shown clear connections between stress and the mental disorder of schizophrenia. While most researchers understand that there are genetic predispositions in those who develop schizophrenia, they generally realize that environmental factors combine with this inherited vulnerability to produce the disorder. In other words, stress contributes to the formation and perpetuation of schizophrenia. It effects the person’s cognitive appraisal of the environment, which when fused with biological predispositions give rise to serious mental distress and distortions.
R. Lewine, professor in the department of psychological and brain sciences at the University of Louisville, gives a good review of the kinds of stress that research has clearly connected with the development of schizophrenic thought patterns (Lewine, 2005). Such stressors include childhood trauma (e.g., parental loss) or confusing family relations involving hyper-criticism, emotional over-involvement, and hostility. Further, the manifestation of schizophrenia itself is a source of stress owing to the external and uncontrollable nature of hallucinations and the “direct distortions in information processing, affect, and interpersonal relationships” (Lewine, 2005, p. 291). Schizophrenics tend to find social life more threatening than the average person. As a result of this, stress is increased and negatively impacts their rational capacities. Another contributing impact of stress on schizophrenic thinking is social stress and poverty, both of which contribute to demoralization, low self-esteem, alienation, and further life hardship since it creates such things as financial worry. In sum, the extreme case of schizophrenia illustrates firmly how stress can impact thinking and mental processes (even if associated with genetic predispositions) by contributing to distorted interpretations of the environment and cognitive impairment that is stress sensitive and threat-oriented.
Memory is another important area of the mind that stress affects. Neuroscientists have shown that the areas of the brain associated with memory are vital in the stress response and are sensitive to stress. Bremner (2002) states, “One important outcome is long-term dysregulation of the brain chemical systems that we need to survive the immediate threat to our lives” (p. 107). The result of stress can cause serious fragmented memory and dissociation because it affects the hippocampus where memory is controlled. Other studies show that cortisol released during stress impairs memory, producing the spaced out feeling an individual feels when under chronic stress, while adrenaline acutely increases memory. This has been shown by administering a stressful math test to subjects with varying levels of cortisol and measuring performance (Lovallo & Thomas, 2000). In each case, cortisol effected hippocampal memory and impaired performance. When stress impacts memory, therefore, the general cognitive state of an individual declines significantly.
Chronic stress interferes with emotional patterns as well. These are obviously linked with thought patterns in a complex relationship. One of the classic studies of psychological stress was conducted on monkeys. John Mason at the Walter Reed Army Institute of Research in the 1950s established beyond question that monkeys were more distressed, and released more stress hormones, by anticipating a stressful shock (which they were trained to avoid by pressing a lever but without knowing when the shock would come) than by receiving the shock itself (cited in McEwen, 2002, p. 48). The experiment concluded that heightened responsibility, uncertainty, and unpredictability elevate stress hormone levels as one would expect. Further research into the relation of stress and emotions has determined that circumstances of frustration, failure, and danger produce brain reactions that lead to the activation of cortisol, which is associated with negative emotions (Lovallo & Thomas, 2000, p. 352). The opposite of a stressful response is one in which a person positively believes in control, is motivated by achievable reward, and able to successfully attain a goal. There seems to be a connection, therefore, between higher levels of cortisol released during periods of lasting stress and negative affectivity. Both physiologically and psychologically, stress has a dampening effect on human emotions.
This is further indicated by one of the notable and overt emotional effects of chronic stress: an increased likelihood of depression. Scientists at the Max Planck Institute of Psychiatry have linked this increased likelihood of depression with both genetics and the role that external stressors exert on the hypothalamic-pituitary-adrenocortical axis (Modell & Holsboer, 2005). Stress triggers the release of cortisol from the brain through the nervous system, which becomes pathological due to a dysfunctional feedback system within the HPA axis. The release of the hormone is not cut off sufficiently by proper feedback from the brain system. Symptoms of depression result, such as intense anxiety, feelings of worthlessness and helplessness, appetite loss, lack of interest or motivation, increased agitation, and emotional apathy. What is most important is that these emotional alterations are the direct result of a neural response to chronic stress. They are mimicked in studies of animal models of depression in chronically stressful situations such as neonatal maternal separation (Ladd et al., 2004). The specific type of stress is not as important as the emotional distress it triggers in the amygdala and hippocampus, key brain structures that are thought to control mood and the emotional interpretation of sense input (Wallenstein, 2003, p. 161). The regulatory mechanism does not shut down and keeps pumping out cortisol since the HPA and limbic regions are not signaling it to stop. As a result of stress, then, the emotions become imbalanced.
A link has been suggested, in addition, between stress and social behavior according to researchers at University of California Los Angeles. In laboratory studies, Taylor and Gonzaga (2007) have developed a model that proposes how human affiliation is driven as a response to stress. It explains the social impulse as a biological response signaled through the neuropeptide oxytocin. This biological marker tells the person suffering from stress that their social network cannot meet the challenges of stress they are facing. As a result, the person feels inclined to eliminate that gap through social behavior, which in turn reduces psychological stress. The positive social contact, inspired in a situation of stress combined with overly low social resources, may help reduce stressful emotion and repair the person to neurocircuitry balance. In other words, neurocircuitry provides the brain and body with signals for seeking human interaction or bonding in times of enduring emotional stress. When social affiliation does not occur, stress becomes both chronic and harmful to the individual as a result of inhibiting the natural brain cycle that could alleviate the stress through social friendships.
In sum, the effects of chronic and traumatic stress are damaging and can be debilitating. Chronic stress has a negative impact on the body and brain, causing the brain to release higher levels of hormones such as cortisol than the body needs. These higher hormone levels harmfully affect various parts of the body, including the immune system, the stomach, the heart, and the liver. Early traumatic stress can exacerbate this problem by leading to perpetual patterns of hyperstress that eventually wear these bodily organs down. In addition to physical effects, chronic stress promotes negative and self-perpetuating cognitive patterns. These have been associated by medical researchers with brain chemistry. Distressful circumstances are often interpreted in ways that are destructive to life and intellectual health. The most extreme example of this, perhaps, is the contributing effect of stress in schizophrenia. In turn, negative schemas and beliefs affect emotions negatively. Chronic stress creates brain patterns that perpetuate, both physically and intellectually, high levels of frustration, anxiety, and discontent. Depression is a common result in those suffering chronic stress, with its concomitant apathetic and dark emotions. In such cases, what may be the natural remedy for stress-positive social affiliation-is ignored or unachieved, thus allowing the maladjustive thoughts and emotions to continue. While there is a strong neurological basis for stress reactions in humans, chronic exposure to environmental stress can have all these harmful effects. Prolonged stress is unnatural and brain chemistry seems not able to adapt well in many cases to it. Although not everything is understood about the brain’s function under stressful events, there seems to be enough scientific evidence to claim that chronic stress is undeniably detrimental to human physical and psychological well-being.
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