Psychological Stressors as Interventions: Good Out of the Evil
A comprehensive definition of stress is a difficult task to achieve. Philosophers such as Hippocrates and biologists like Hans Selye (2) attempted to define stress, however it is yet to be precisely embodied. Although stress is something which we may not define with clarity and pervasiveness but we could perceive it. Perhaps this is the best way to present stress to initiate the current review. However for scientific purpose of this review we need to take a more objective outlook towards stress. Traditionally stress comes in various forms which include exercise, fasting, fright, temperature, high altitudes, bleeding infection, surgery, trauma, disease, weaning, nutrition, social reorganization, and environmental effects. We can thus derive from preceding discussion that stress is a state of threatened balance, equilibrium or harmony that eventually disturbs the homeostasis of the body. Stress can be of different kinds such as psychological, physiological, emotional, and social stress as well as due to infections. Further studies are required however to quantitate, characterize and distinguish these various stresses
To address this issue intuitively, we have considered a situation involving psychological stress. The state of psychological stress can initiate from or lead to emotional stress or a social stress or in certain cases a state of physiological stress as well. Therefore, any present stressed state, here psychological stress state in broader perspective may be preceded or succeeded by another stress state. However, the question is where to draw line between all these stresses. This becomes especially important in scientific studies where one may not be able to exclude not so obvious correlation between different stresses. Thus at one point of time it becomes really difficult to explain which kind of stress is actually under scientific study. This further limits the exact interpretation of multiple stress related states which again may not be independently corresponded to an individual stress. The main reason for this anomaly is lack of defined set of criteria based on which we can address the kinds of stress. This is probably because not many attempts have been made in the field of understanding stress with respect to predefined biological conditions based on a set of biomarkers which are expressed in different stressed states. Although the studies have been done which particularly emphasize on cortisol as a biomarker for stress but there are certain limitations to it such as (a) cortisol concentrations fluctuate, (b) cortisol may not distinguish between different kinds of stress. This molecular status of stress research warrants further experimentation to establish more reliable markers for stress. To the best of our knowledge, only a few groups have tried to relate some more reliable biomarkers to a stressed state including some proteins, metabolites, and metallic components in murine and bovine models (3-6). But it certainly remains to be further established that what are the biological conditions associated to different stress based on which we can classify them precisely. This impreciseness in defining and distinguishing between different kinds of stress can be dealt with by addressing stressors related to a particular condition. The advantage of defining stressors is that the level of confusion regarding the stress under study boils down to minimum because now the cause for a stressed state is precisely defined and hence the state. Stressors are of many kinds such as psychological, social, peer pressure, physiological, infectious, traumatic and nutritional. Hence, unlike psychological stress, PS precisely defines the consequent state under study while simultaneously being specific on its cause. Thus at any instant of time, it is known which stressor and stressor associated state is being referred to irrespective of the broad category of stress they belong to. Hence, to summarize in brief while stress is a state, stressor is the cause and can be addressed independently. Based on above discussion, it is now clear that it is perhaps easier to understand stress in context of different stressors. Hence, in the review, the term “stressors” will be mostly used to address the different stimuli related to state of psychological stress.
Distinction between chronic and acute stressors
There is a necessity to bring out a clear distinction between acute and chronic stressors that arises from the fact that both kinds of stressors may have different consequences on the stressed state. As a result the experimental aftermath and interpretations are dependent both on the type of stressors as well as the effects these stressors produce. For instance, it is possible in some cases that the effects of a stressor response may not last long enough (i.e. are acute) or express immediately to significantly affect a diseased state. In such a situation, it becomes important to concentrate on the effects of stressors which are relatively long lasting (i.e. chronic) and express over a period of time. Hence, it becomes mandatory to distinguish the two on all possible grounds (7-10). In fact, Elliot and Eisdorfer’s (1982) taxonomy characterizes stressors on the basis of duration and course and strongly discriminate between acute and chronic stressors (11). Considering the literal meaning of the words, chronic and acute stressors are distinguished based on temporal differences. Chronic stressors are the ones which are persistent unlike acute stressors which only stay for a shorter duration. Similarly, it can be stated for the effects of stressors while adding further to it that chronic effects of a stress could be recurrent. It simply means that in case of chronic effects the symptoms of a stressed state may reoccur during the lifetime of the individual. It is to be made clear here that it is not always true that an acute stress leads to acute effects i.e. the effects that last for a relatively shorter duration. (12-15) Based on this explanation it now becomes clear that acute and chronic effects of stressors are not only defined temporally but also distinction has to be made more precisely on the basis of set of biomarkers that again are qualitatively and quantitatively distinct in both conditions. This identification of markers for acute and chronic effects of stressors will not only mark a distinction between the two but will also help in quick diagnosis of the type of stressor effects and hence its consequences which can be markedly different for the two cases. (7, 16) For example the expression of acute phase proteins or expression of certain proteins for a longer time or some other class of proteins can result in two completely different physiological consequences. Besides its significance, only a very few studies clearly mention the kind of stressors and stressor effects under study. (17-19). It is perhaps due to reasons as mentioned above that the boundary between acute and chronic stressors is not yet well defined and it is difficult to identify them. Following the argument, the sharp distinction related to effects of chronic and acute stressors is not well taken in the review, though they have been put into focus when required.
PSYCHOLOGICAL STRESSORS AND DISEASES
It has always been a common observation that people who tend to be psychologically strong and sound seem to fight with their diseases better or the other way round. That is people who are under a stressed state appear to be more susceptible to diseases. This was the basic idea behind reviewing the research so far been done in this regard. The main aim was to look for the studies which show any kind of correlation positive, negative or nil between disease and stress. And if there is then, are there any further studies where the possible mechanism of how stress affects a diseased state has been highlighted or worked out. The results of search were really interesting but scattered. So, here we have tried to put them in a basic scaffold from where they can be further worked out to complete the infrastructure. Following are some of the studies related to stress and diseases which highlight the role of stress in some very important and most prevalent of the diseases like AIDS, cancer, diabetes. On the other hand some studies not exactly with the diseases rather than on different aspect of wound recovery, inflammation and healing.
AIDS and stressors
According to most recent surveys done in 2006 an estimated of 39.5 million individuals were diagnosed with HIV infection worldwide. AIDS diagnosis as well as progression is equally stressful as cancer. In fact, there is now a growing population of people of HIV-infected people who face both disease-specific and general life stressors because of increasing dependence on stringent treatments for maintaining an optimal health which are really demanding both physically and psychologically. Besides this, AIDS add up to higher degree of social stressors as well as peer pressure. Due to lack of adequate knowledge of the disease in people of the society they are more reluctant to accept AIDS patients that add another level of difficulties for them. Moreover, due to the reduced support and increased dissatisfaction in the relation with one AIDS suffering partner the psychological state of patient is further worsened. From above, it is thus easily comprehensible that the kinds of stressors in cancer and AIDS are almost similar. Hence, the studies to see the effect of stress on disease progression and increased survivability are also similar to certain extent.The very first studies that actually demonstrated the effects of stress and social support on AIDS progression was done by Jane Lesserman et al, 1999 where they demonstrated a positive correlation of stressful life events, reduced social support and cumulative depressive symptoms with disease progression. (36, 37) In continuation with these primary studies, as is the case with cancer, the relation of stressors with AIDS has been highlighted with respect to consequences of psychological interventions on progression of AIDS. Adam W. Carrico and Michael H. Antoni (38) have evaluated the effect ofvarious psychosocial interventions on stress hormone levels of HIV-infected population. The group took into consideration number of interventions, viz. cognitive stress behavioral management, written emotional expression interventions, and relaxation training and meditation based interventions. The studies were part of long term follow-up and hence to be more confidant with the changes observed during psychological interventions, besides monitoring CD4+ cell count and viral load, the ability of lymphocytes to proliferate when challenged by antigens (like plant mitogens viz. Phytohemagglutinin (PHA)) as it may partially compensate for CD4+ cells decline during HIV progression was tracked. Similarly, NK cell count as well as NKCC was monitored as they are also known to have a compensatory role for reduced CD4+ counts. Besides considering IgG antibody levels in response, secondary infections were also taken into consideration. In this trial of CBSM done on randomized group of gay men, HIV positive men who received CBSM displayed significant increases in CD4+ cell counts, NK cells, PHA lymphocyte responses and NKCC pre to post notification of disease. Another collection of behavioral studies have suggested that a composite of three positive psychological resources viz. positive effect, finding meaning, and positive or optimistic expectancy was negatively related to mortality and immune system decline (CD4+ cell counts) during a five year follow up with a percentage of 6% non-survivors who had all three resources versus 17% of population of people who did not have it. In fact optimism has been examined as the predictor of disease progression in five studies with one study providing a proof that patients with moderate optimism had the highest CD4+ cell counts.(39)In a study by Ironson et al (40), they found a linear relationship of optimism with CD4+ cell counts and viral load suppression. At this point, it is necessary to mention that according to recent findings, with a high state of optimism, there is an increased probability of acquiring a stressed state. This has been attributed to the violation of optimists’ positive expectancies and subsequent disappointment, but empirical evidence suggests that it is more likely to be a consequence of optimists’ greater engagement during difficult stressors. (41) Hence, the validation of linear relationship of stress and optimism has to be reconsidered. In fact in the study by Milan et al with 412 HIV Infected men and women a curvilinear relationship between optimism and CD4 cell decline was found. (36)Similar studies on HIV positive men with hemophilia found that having an optimist outlook predicted lower mortalityset of contradictory results of studies done with a group of 74 gay men and 47 men found no relationship between dispositional optimism and disease progression although the latter study found that optimistic explanatory style was related to a faster decline in CD4+ cell counts during a 2-year follow-up. (43, 44)Hence, it becomes important to consider the moderate level of optimism as well as mode of its expression especially while explaining such contradictory studies. Although these findings are mixed, the larger and more recent studies showed a positive relationship between moderate optimism and better health outcomes. Spirituality viewed as another type of coping when adopted by a group of men and women with and without HAART showed slower decline in CD4+ cell counts and better control over viral load similar to optimism studies. (40) Another aspect that was looked for in the same studies was effects of emotional expression on the health of people with HIV. It was reported that while emotional expression (during writing about a trauma) was beneficial for CD4+ counts and viral load, depth processing (emotional/cognitive processing) was even better. (40)Similar positive effects on CD4+ cell counts and viral load were associated with personality traits like openness, conscientiousness, extraversion, agreeableness, and neuroticism which may again be correlated with better stress relief (45) and hence the consequences. An important emphasis has to be given here on the mixed results observed related to different intervention studies affecting CD4+ cell counts. According to five major studies on interventions affecting CD4 counts (one of the marker of HIV infection) (46-50)and one study on natural killer cells as an immune status marker did not show any difference among treated and control groups. A limitation of the studies concerns the fact that analysis did not control for patients’ medical status and HAART medication adherence. Besides this the studies on cytotoxic T cells activity as well as population showed mixed results. (51) The above uncertainties may be a result of certain experimental limitations which have been overcome by time. As an example many of the negative studies did not observe improvements in some indicators of psychosocial adaptation, neither there was an evidence of reduced depression. Moreover, the affects of modulated immune system may not be direct and hence other immune components may be taken into consideration as mentioned above.
Obesity and stressors
The increased risk of obesity has been related to exposure to chronic stressors, such as job strain and negative psychological states such as depression besides the social factors like personal income, educational attainment and occupational status. Although the poorer health behaviors such as physical inactivity and dietary fat intake (58) associated with various PSs can be attributed to increased obesity risks. However, some findings suggest that adjusting to beneficial behaviors only minimally lead to a reduced obesity risk factor. Hence, it becomes essential to explore the stress mediated mechanisms related to high risk factor of obesity. The studies done in this regard by Mark Hamer and Emmanual Stamataki (59) suggest a contribution of inflammatory markers produced during a stressed state to obesity. Indeed adipose tissue is one of the major sites of release of inflammatory markers such as Interleukins and acute phase proteins. Hence, the secretion of certain pro-inflammatory cytokines like TNF-α and interleukins in the respective adipose tissue after a stressor stimulus may play a causal role in obesity. TNF-α may be involved in this through the regulation of free fatty acid levels, leptin production, glucose transporter numbers and insulin receptor activity and may influence the major nuclear factors involved in adipocyte growth, differentiation and function. In other words cytokines are thought to be involved in the regulation of metabolism and food intake thus possibly impacting on health behaviors
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