Showing papers on "Stressor published in 2011"

The serotonin transporter promoter variant (5-HTTLPR), stress, and depression meta-analysis revisited: evidence of genetic moderation.

Abstract: The principal function of the serotonin transporter is to remove serotonin from the synapse, returning it to the presynaptic neuron where the neurotransmitter can be degraded or re-released at a later time. A polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been found to affect the transcription rate of the gene, with the short (s) allele transcriptionally less efficient that the alternate long (l) allele. In 2003, Caspi and colleagues examined the relationship between 5-HTTLPR, stress and depression using a prospective, longitudinal birth cohort and found that subjects carrying the less functional 5-HTTLPR s allele reported greater sensitivity to stress1. This study has been cited over 2000 times in the scientific literature and generated a great deal of excitement and controversy around the potential of gene × environment interaction studies2. To date, there have been 55 follow-up studies, exploring whether 5-HTTLPR moderates the relationship between stress and depression, with some studies supporting the association between the 5-HTTLPR s allele and greater stress sensitivity and others not. Two recent meta-analyses have assessed a subset of these studies and concluded that there is no evidence supporting the presence of genetic moderation3, 4. Since their publication, these meta-analyses have been criticized for only including a subset of the studies investigating the relationship between 5-HTTLPR stress and depression5–9. In fact, while 56 primary data studies have assessed whether 5-HTTLPR moderates the relationship between stress and depression, the Munafo and Risch meta-analyses included only 5 and 14 of those studies respectively10–48. Further, Uher and McGuffin have demonstrated that the larger, Risch meta-analysis included a significantly greater proportion of negative replication studies than positive replication studies8. There are multiple reasons that the studies included in the meta-analyses were limited. First, the primary study data needed for traditional meta-analysis was often not available, either in the original publications or in follow-up email inquiries to study authors. For instance, Munafo and colleagues reported that 15 studies met criteria for inclusion in their meta-analysis. However, they were only able to obtain the primary study data needed for inclusion for five of those studies. There is no evidence that the studies that were able to be included in the meta-analyses were of higher “quality” than those not included. Another reason why many studies were not included in the Risch and Munafo meta-analysis is that both meta-analyses focused exclusively on studies that explored an interaction between 5-HTTLPR and stressful life events (SLEs) in the development of depression. The original Caspi article, however, not only reported an interaction between 5-HTTLPR and SLEs, but also an interaction between 5-HTTLPR and childhood maltreatment stress. Nine studies have attempted to replicate this interaction with childhood maltreatment, but these studies were not included in the meta-analyses. Some observers have noted that the SLE study design may have limited power to detect genetic moderation effects because they are susceptible to biases introduced by impaired recall of stressors by subjects and highly variable stressors between subjects9, 45. A newer class of studies has attempted to bypass these potential problems by focusing on specific populations that have experienced a substantial, specific stressor. These studies test whether 5-HTTLPR moderates the relationship between a specific stressor and depression. Eighteen studies have employed such specific stressor designs, but like the childhood maltreatment studies, these studies were excluded from the previous meta-analysis. In this study, rather than focus on a limited of studies, we sought to perform a meta-analysis on the entire body of work assessing the relationship between 5-HTTLPR, stress and depression. Unfortunately, different types of studies have generally used different study designs to explore this question, rendering it very difficult to combine the studies into a single traditional meta-analysis. An approach useful in situations where equivalent raw data are not available across all studies, is to combine the studies at the level of significance tests 49. The Liptak-Stouffer Z-score method is a well-validated method for combining p-values across studies that has been utilized widely across genomics and biostatistics 50–56. In this study, we utilize the Liptak-Stouffer Z-score method to combine the results from studies investigating whether the 5-HTTLPR variant moderates the relationship between stress and depression.

Exposure to a Social Stressor Alters the Structure of the Intestinal Microbiota: Implications for Stressor-Induced Immunomodulation

Abstract: The bodies of most animals are populated by highly complex and genetically diverse communities of microorganisms. The majority of these microbes reside within the intestines in largely stable but dynamically interactive climax communities that positively interact with their host. Studies from this laboratory have shown that stressor exposure impacts the stability of the microbiota and leads to bacterial translocation. The biological importance of these alterations, however, is not well understood. To determine whether the microbiome contributes to stressor-induced immunoenhancement, mice were exposed to a social stressor called social disruption (SDR), that increases circulating cytokines and primes the innate immune system for enhanced reactivity. Bacterial populations in the cecum were characterized using bacterial tag-encoded FLX amplicon pyrosequencing. Stressor exposure significantly changed the community structure of the microbiota, particularly when the microbiota were assessed immediately after stressor exposure. Most notably, stressor exposure decreased the relative abundance of bacteria in the genus Bacteroides, while increasing the relative abundance of bacteria in the genus Clostridium. The stressor also increased circulating levels of IL-6 and MCP-1, which were significantly correlated with stressor-induced changes to three bacterial genera (i.e., Coprococcus, Pseudobutyrivibrio, and Dorea). In follow up experiments, mice were treated with an antibiotic cocktail to determine whether reducing the microbiota would abrogate the stressor-induced increases in circulating cytokines. Exposure to SDR failed to increase IL-6 and MCP-1 in the antibiotic treated mice. These data show that exposure to SDR significantly affects bacterial populations in the intestines, and remarkably also suggest that the microbiota are necessary for stressor-induced increases in circulating cytokines.

Stress and immune modulation in fish.

Abstract: Stress is an event that most animals experience and that induces a number of responses involving all three regulatory systems, neural, endocrine and immune. When the stressor is acute and short-term, the response pattern is stimulatory and the fish immune response shows an activating phase that specially enhances innate responses. If the stressor is chronic the immune response shows suppressive effects and therefore the chances of an infection may be enhanced. In addition, coping with the stressor imposes an allostatic cost that may interfere with the needs of the immune response. In this paper the mechanisms behind these immunoregulatory changes are reviewed and the role of the main neuroendocrine mechanisms directly affecting the building of the immune response and their consequences are considered.

Violence against nurses and its impact on stress and productivity.

Abstract: The purpose of this study was to examine how violence from patients and visitors is related to emergency department (ED) nurses' work productivity and symptoms of post-traumatic stress disorder (PTSD). Researchers have found ED nurses experience a high prevalence of physical assaults from patients and visitors. Yet, there is little research which examines the effect violent events have on nurses' productivity, particularly their ability to provide safe and compassionate patient care. A cross-sectional design was used to gather data from ED nurses who are members of the Emergency Nurses Association in the United States. Participants were asked to complete the Impact of Events Scale-Revised and Healthcare Productivity Survey in relation to a stressful violent event. Ninety-four percent of nurses experienced at least one posttraumatic stress disorder symptom after a violent event, with 17% having scores high enough to be considered probable for PTSD. In addition, there were significant indirect relationships between stress symptoms and work productivity. Workplace violence is a significant stressor for ED nurses. Results also indicate violence has an impact on the care ED nurses provide. Interventions are needed to prevent the violence and to provide care to the ED nurse after an event. Language: en

Stress amongst dental students: a systematic review

Abstract: The present study was conducted to provide future researchers and dental educators with an overview of stress amongst undergraduate dental students reported in the literature. This overview is needed for the development of a new questionnaire measuring the level of stressors including students, staff and process of dental education. In addition, the review can be used to modify dental curricula to decrease such stress and produce better dentists. Our study consisted of a systematic review of 49 peer-reviewed articles published between 1966 till October 2008 in English, discussing different aspects of stress amongst undergraduate dental students. These aspects are demographic variables of stress, sources of stress, impact of stress, indicators of stress, instruments measuring stress level and management of stress. Major sources of reported stress were related to examinations, clinical requirements and dental supervisors. Studies suggest using signs and symptoms for early detection of stress and proper intervention.

Linking psychosocial stressors and childhood obesity.

Abstract: Research has established a wide array of genetic and environmental factors that are associated with childhood obesity. The focus of this review is on recent work that has established the relationship between one set of environmental factors, stressors and childhood obesity. These stressors are particularly prevalent for low-income children, a demographic group that has high rates of obesity in the USA and other developed countries. In this review, we begin by summarizing the psychosocial stressors faced by children followed by health outcomes associated with exposure to these stressors documented in the literature. We then summarize 11 articles which examined the connection between psychosocial stressors in the household and obesity and eight articles which examined the connection between individual psychosocial stressors and obesity. Policy recommendations emerging from this research include recognizing reductions in childhood obesity as a potential added benefit of social safety net programmes that reduce financial stress among families. In addition, policies and programmes geared towards childhood obesity prevention should focus on helping children build resources and capacities to teach them how to cope effectively with stressor exposure. We conclude with suggestions for future research.

A within‐individual study of interpersonal conflict as a work stressor: Dispositional and situational moderators

Abstract: Summary Focusing on interpersonal conflict as a work stressor, the authors used a within-subjects research design to examine the effect of conflict episodes on employees’ negative affect on the job. The roles of agreeableness and social support in moderating the negative effects of conflict episodes were also examined. A two-week experience-sampling study revealed that interpersonal conflict influenced employees’ intraindividual fluctuations in negative affect. As predicted, agreeableness and social support influenced individuals’ patterns of affective responses to conflict, such that conflict was more strongly associated with negative affect for agreeable employees, and for thosewith lower levels of social support at work. Overall, the results suggest that both personality (agreeableness) and context (social support) significantly moderate the affective implications of interpersonal conflict at work. Copyright # 2010 John Wiley & Sons, Ltd.

The Trier Social Stress Test protocol for inducing psychological stress.

Abstract: This article demonstrates a psychological stress protocol for use in a laboratory setting. Protocols that allow researchers to study the biological pathways of the stress response in health and disease are fundamental to the progress of research in stress and anxiety.1 Although numerous protocols exist for inducing stress response in the laboratory, many neglect to provide a naturalistic context or to incorporate aspects of social and psychological stress. Of psychological stress protocols, meta-analysis suggests that the Trier Social Stress Test (TSST) is the most useful and appropriate standardized protocol for studies of stress hormone reactivity.2 In the original description of the TSST, researchers sought to design and evaluate a procedure capable of inducing a reliable stress response in the majority of healthy volunteers.3 These researchers found elevations in heart rate, blood pressure and several endocrine stress markers in response to the TSST (a psychological stressor) compared to a saline injection (a physical stressor).3 Although the TSST has been modified to meet the needs of various research groups, it generally consists of a waiting period upon arrival, anticipatory speech preparation, speech performance, and verbal arithmetic performance periods, followed by one or more recovery periods. The TSST requires participants to prepare and deliver a speech, and verbally respond to a challenging arithmetic problem in the presence of a socially evaluative audience.3 Social evaluation and uncontrollability have been identified as key components of stress induction by the TSST.4 In use for over a decade, the goal of the TSST is to systematically induce a stress response in order to measure differences in reactivity, anxiety and activation of the hypothalamic-pituitary-adrenal (HPA) or sympathetic-adrenal-medullary (SAM) axis during the task.1 Researchers generally assess changes in self-reported anxiety, physiological measures (e.g. heart rate), and/or neuroendocrine indices (e.g. the stress hormone cortisol) in response to the TSST. Many investigators have adopted salivary sampling for stress markers such as cortisol and alpha-amylase (a marker of autonomic nervous system activation) as an alternative to blood sampling to reduce the confounding stress of blood-collection techniques. In addition to changes experienced by an individual completing the TSST, researchers can compare changes between different treatment groups (e.g. clinical versus healthy control samples) or the effectiveness of stress-reducing interventions.1

A Qualitative Study of the Sources and Impact of Stress Among Urban Teachers

Abstract: Although urban teachers are at-risk of experiencing significant work-related stress, urban teacher stress has been neglected in the research literature to date. Through semi-structured interviews conducted with a sample of K-4 urban teachers (N = 14) from three high-poverty schools in a large, Midwestern city, we examined teachers’ perceptions regarding sources and impact of stress and the resources needed to address identified stressors. Results from consensual qualitative research (CQR; Hill et al. in Couns Psychol, 25:517–572, 1997; Hill et al. in Consensual qualitative research: an update, 2005) suggest that at least one-half of the cases identified lack of resources, excessive workload, school-level disorganization, managing behavior problems, and accountability policies as significant sources of stress. The majority of teachers reported that occupational stress significantly impacted their personal relationships and physical health, and teachers identified human and material resources as most important to reducing work-related stress. Implications for organizationally based interventions and school policies to address urban teacher stress are discussed.

Inflexibly focused under stress: Acute psychosocial stress increases shielding of action goals at the expense of reduced cognitive flexibility with increasing time lag to the stressor

Abstract: Dynamically adjusting the right amount of goal shielding to varying situational demands is associated with the flexibility of cognitive control, typically linked with pFC functioning. Although stress hormones are found to also bind to prefrontal receptors, the link between stress and cognitive control remains elusive. Based on that, we aimed at investigating effects of acute psychosocial stress on dynamic control adjustments. Forty-eight healthy volunteers were exposed to either a well-established stress induction protocol (the Trier Social Stress Test, TSST) or a standardized control situation before a selective attention (Simon) task involving response conflicts. The individual physiological stress response was monitored by analyzing levels of free cortisol and α-amylase activity in saliva samples showing that the TSST reliably induced an increase of endogenous stress hormone levels. Acute stress did not inevitably impair cognitive functioning, however, as stressed participants showed tonically increased goal shielding (to reduce interference) at the expense of decreased cognitive flexibility. Importantly, as a novel finding in humans, stress effects on cognitive functions were not present immediately after the stress experience but developed gradually over time and, therefore, paralleled the time course of the hypothalamus-pituitary-adrenal (HPA) stress response. In addition, the total increase of individual cortisol levels reflecting HPA activity, but not the total changes in α-amylase activity associated with sympathetic activity, was reversely related to the amount of cognitive flexibility in the final block of testing. Our study provides evidence for a stress-induced time-dependent decrease of cognitive flexibility that might be related to changes in cortisol levels.

Stress and coping strategies of students in a medical faculty in malaysia.

Abstract: Background: Stress may affect students’ health and their academic performance. Coping strategies are specific efforts that individuals employ to manage stress. This study aimed to assess the perception of stress among medical students and their coping strategies. Methods: A cross-sectional study was conducted among 376 medical and medical sciences undergraduates in Management and Science University in Malaysia. Stress was assessed by a global rating of stress. Sources of stress were assessed using a 17-item questionnaire. The validated Brief COPE inventory was used to assess coping strategies. Results: The majority of respondents were females (64.4%), aged 21 years or older (63.0%), and were Malays (68.9%). Forty-six percent felt stress. The most common stressor was worries of the future (71.0%), followed by financial difficulties (68.6%). Significant predictors of stress were smoking (OR = 2.9 , 95% CI 1.3–6.8, P = 0.009), worries of the future (OR = 2.1 , 95% CI 1.3–3.4, P = 0.005), self-blame (OR = 1.3, 95% CI 1.1–1.5, P = 0.001), lack of emotional support (OR = 0.8, 95% CI 0.7–0.9, P = 0.017), and lack of acceptance (OR = 0.8, 95% CI 0.6–0.9, P = 0.010). Students used active coping, religious coping reframing, planning, and acceptance to cope with stress. Conclusion: Stressors reported by the students were mainly financial and academic issues. Students adopted active coping strategies rather than avoidance. Students should receive consultation on how to manage and cope with stress.

Altered stress responses in children exposed to early adversity: a systematic review of salivary cortisol studies.

Abstract: Pathological stress responses are implicated in numerous disorders. Hypothalamic-pituitary-adrenal axis function is influenced by gene-environment interaction, with early-life environmental adversity having long-lasting effects. We examine the evidence that, in humans, these effects are apparent from infancy. We systematically reviewed published findings on cortisol response to a stressor, in 0-5-year-olds already exposed to adversity. Adversity was defined as a negative environmental influence present post-conception. We searched Ovid MEDLINE (1950-May 2010), EMBASE (1980-May 2010) and PsychINFO (1806-May 2010). We included peer-reviewed, English language studies that analysed salivary cortisol before and after a standardised stressor. We identified 30 studies, of which 27 reported a significant effect of adversity on the cortisol response to stress. Six of these demonstrated an effect of prenatal substance exposure. Thirteen studies found that psychosocial adversity increased cortisol reactivity. Three studies reported that cortisol reactivity could be normalised by intervention programmes. The studies were heterogeneous, both in nature of adversity studied and in stressor used, precluding meta-analysis and assessment of publication bias. Our review presents evidence that adversity disrupts the stress response from an early age. Longitudinal studies are required to determine whether effects persist, alter with time, or are reversible with intervention.

Unraveling the daily stress crossover between unemployed individuals and their employed spouses.

Abstract: This study examined the dynamic relationship of distress levels between spouses when one is unemployed (and looking for a job) while the other is engaged in full-time employment. Using the diary survey method, we sampled 100 couples in China for 10 days and tested a model comprising three stress crossover mechanisms: the direct crossover, the mediating crossover, and the common stressor mechanisms. Results supported the direct crossover and common stressor mechanisms. Other stressors (e.g., work–family conflict and negative job search experience) were also related to distress of the unemployed individuals and their employed spouses. Additionally, we found a three-way interaction involving gender, marital satisfaction, and distress levels of employed spouses. We discuss how the study contributes to the unemployment and stress crossover literatures.

Stress resilience in early marriage: can practice make perfect?

Abstract: As all couples experience stressful life events, addressing how couples adapt to stress is imperative for understanding marital development. Drawing from theories of stress inoculation, which suggest that the successful adaptation to moderately stressful events may help individuals develop a resilience to future stress, the current studies examined whether experiences with manageable stressors early in the marriage may serve to make the relationship more resilient to future stress. In Study 1, 61 newlywed couples provided data regarding their stressful life events, relationship resources (i.e., observed problem-solving behaviors), and marital satisfaction at multiple points over 21⁄2 years. Results revealed that among spouses displaying more effective problem-solving behaviors, those who experienced moderate stress during the early months of marriage exhibited fewer future stress spillover effects and reported greater increases in felt efficacy than did spouses who had less experience with early stress. Study 2 examined stress resilience following the transition to parenthood in a new sample of 50 newlywed couples. Again, spouses who experienced moderate stress during the early months of marriage and had good initial relationship resources (i.e., observed support behaviors) reported greater marital adjustment following the transition to parenthood than did spouses who had good initial resources but less prior experience coping with stress. Together, results indicate that entering marriage with better relationship resources may not be sufficient to shield marital satisfaction from the detrimental effects of stress; rather, couples may also need practice in using those resources to navigate manageable stressful events.

Daily Cognitive Appraisals, Daily Affect, and Long-Term Depressive Symptoms: The Role of Self-Esteem and Self-Concept Clarity in the Stress Process:

Abstract: The current study investigated how self-esteem and self-concept clarity are implicated in the stress process both in the short and long term. Initial and 2-year follow-up interviews were completed by 178 participants from stepfamily unions. In twice-daily structured diaries over 7 days, participants reported their main family stressor, cognitive appraisals (perceived stressor threat and stressor controllability), and negative affect. Results of multilevel modeling indicated that high self-esteem ameliorated the effect of daily negative cognitive appraisals on daily negative affect. Self-concept clarity also buffered the effect of low self-self-esteem on depressive symptoms 2 years later. Our findings point to the vulnerability of those having low self-esteem or low self-concept clarity in terms of both short- and long-term adaptation to stress. They indicate the need for the consideration of such individual differences in designing stress management interventions.

A study on stress, stressors and coping strategies among Malaysian medical students

Abstract: Introduction: The milieu of tertiary education has always been regarded as a highly stressful environment for students especially for medical students. The study aims to explore the stress level, stressors, and coping strategies among first year medical students in Malaysian public universities and factors contributed to the stress at the end of year. Methodology: A multicenter cross-sectional study involving four Malaysian public universities. The 12-item General Health Questionnaire (GHQ-12), Medical Student Stressor Questionnaire (MSSQ) and Brief COPE inventory were self-administered to measure stress level, sources of stress and coping strategies respectively among the participants. Calculated sample size was 387. Results: Out of 387 selected participants, 359 (92.7%) responded to this survey. This study found that the prevalence (at the end of the year) of distressed first year medical students was 50%. The major stressors across the universities were academic-related issues. The top five coping strategies were religion, active coping, positive re- interpretation, acceptance and planning. University, parent income, academic activities, group activities, and desire related stressors were significant factors contributing to the students' stress (p-value < 0.05). Conclusion: This study found that there was a high prevalence of distressed among first year medical students at the end of year, the major stressors were related to academic and contributing factors of stress were related to university, coping strategy, types of stressor and parent income status. Training first year medical students on adaptive coping strategies, managing stressors, and improving peer-group supports to the students will help to improve this condition.

Lifetime and HIV-related PTSD among persons recently diagnosed with HIV.

Abstract: This cross-sectional study sought to determine the percentage of individuals who met criteria for lifetime PTSD and HIV-related PTSD among 85 recently diagnosed HIV-positive patients attending public health clinics in the Western Cape, South Africa. The PTSD module of the Composite International Diagnostic Interview (CIDI) was used to determine the percentage of those who met criteria for lifetime PTSD and HIV-related PTSD. The rate of lifetime PTSD and incidence of HIV-related PTSD was 54.1% (95% CI: 43.6–64.3%) and 40% (95% CI: 30.2–50.6%), respectively. Findings suggest that receiving an HIV-positive diagnosis and/or being HIV-positive may be considered a stressor that frequently results in HIV-related PTSD. Given the various barriers to efficient mental health interventions and services in South Africa, there are significant challenges that need to be addressed in order to ensure that the mental health of HIV-positive individuals is appropriately addressed.

The Impact of Sexual Harassment on Depressive Symptoms during the Early Occupational Career

Abstract: Sexual harassment has been theorized as a stressor with consequences for the physical and mental health of its targets. Though social scientists have documented a negative association between sexual harassment and mental health, few longitudinal studies have investigated the association between sexual harassment and depressive symptoms. Using longitudinal survey data from the Youth Development Study, combined with in-depth interviews, this article draws on Louise Fitzgerald’s theoretical framework, stress theory, and the life course perspective to assess the impact of sexual harassment on depressive affect during the early occupational career. In support of Fitzgerald’s model, our findings confirm that sexual harassment is a stressor that is associated with increased depressive symptoms. Our quantitative results show that women and men who experience more frequent sexual harassment at work have significantly higher levels of depressed mood than non-harassed workers, even after controlling for prior harassment and depressive symptoms. Moreover, we find evidence that sexual harassment early in the career has long-term effects on depressive symptoms in adulthood. Interviews with a subset of our survey respondents point to a variety of coping strategies and reveal further links between harassment and other aspects of mental health, such as anger and self-doubt.

Malleability of attentional bias for positive emotional information and anxiety vulnerability.

Abstract: Recent research supports a causal link between attentional bias for negative emotional information and anxiety vulnerability. However, little is known about the role of positive emotional processing in modulating anxiety reactivity to stress. In the current study, we used an attentional training paradigm designed to experimentally manipulate the processing of positive emotional cues. Participants were randomly assigned to complete a computerized probe detection task designed to induce selective processing of positive stimuli or to a sham condition. Following training, participants were exposed to a laboratory stressor (i.e., videotaped speech), and state anxiety and positive affect in response to the stressor were assessed. Results revealed that individual variability in the capacity to develop an attentional bias for positive information following training predicted subsequent emotional responses to the stressor. Moreover, individual differences in social anxiety, but not depression, moderated the effects of the attentional manipulation, such that, higher levels of social anxiety were associated with diminished attentional allocation toward positive cues. The current findings point to the potential value of considering the role of positive emotional processing in anxiety vulnerability.

Effects of stressors and immune activating agents on peripheral and central cytokines in mouse strains that differ in stressor responsivity.

Abstract: The impact of inflammatory immune activation on behavioral and physiological processes varies with antecedent stressor experiences. We assessed whether immune activation would differentially influence such outcomes as a function of stressor reactivity related to genetic differences. To this end, we assessed the influence of a social stressor (exposure to a dominant mouse) in combination with an acute immune challenge on behavior and on peripheral and central cytokines in stressor-reactive BALB/cByJ mice and the less reactive C57BL/6ByJ strain. As C57BL/6ByJ and BALB/cByJ mice are highly T helper type-1 (Th1) and Th2 responsive, respectively, the stressor effects were assessed in response to different challenges, namely the viral analogue poly I:C and the bacterial endotoxin lipopolysaccharide (LPS). The stressor enhanced the effects of LPS on sickness behaviors and plasma corticosterone particularly in BALB/cByJ mice, whereas the effects of poly I:C, which primarily affects Th1 processes, were not augmented by the stressor. As well, the stressor increased circulating cytokines in LPS treated C57BL/6ByJ mice, whereas the effects of poly I:C were diminished. Finally, like circulating cytokines, mRNA expression of pro-inflammatory cytokines within the prefrontal cortex and hippocampus varied with the mouse strain and with the stressor experience, and with the specific cytokine considered. Together, the experiments indicated that the impact of stressors vary with the nature of the immune challenge to which animals had been exposed. Moreover, given the diversity of the stressor effects on central and peripheral processes, it seems likely that the cytokine changes, HPA activity and sickness operate through independent mechanisms.