Ethnic differences in diurnal cortisol profiles in healthy adults: A meta-analysis.

PURPOSE: Cortisol is a well-known biomarker of the physiological stress system; atypical cortisol patterns have been linked to many psychological and physiological illnesses. Previous studies have found vast health disparities among ethnic groups; however, studies examining the relationship between cortisol and ethnicity have found mixed results. This meta-analysis investigated whether there are differences in diurnal cortisol outcomes among ethnic groups, while considering the moderating roles of various individual factors and methodological approaches. METHODS: Search phrases were entered into MEDLINE, PsycINFO, EMBASE, Cochrane Library, CINAHL, Scopus, and Web of Science. Effect sizes were extracted for ten diurnal cortisol outcomes, including waking, 30 min after waking, cortisol awakening response, slope, area under the curve, urinary twenty-four-hour secretion, total cortisol output, and midday, evening, and bedtime concentrations, for eight ethnic group comparisons, including Asians, Blacks, Hispanics, Indigenous people, Whites, Minority and Majority groups, and Multiethnic groups. Moderator analyses, including variables such as gender, age, and number of cortisol collection time points, were conducted. RESULTS: There were significant ethnic differences in diurnal cortisol profiles, including cortisol awakening responses, with more robust differences in ethnic comparisons that included White participants. Differences in diurnal cortisol profiles were also moderated by gender, mean age, and sample size. CONCLUSIONS: This meta-analysis supports the notion that ethnic groups exhibit distinct diurnal cortisol profiles, which, according to the biopsychosocial model of health, may be a result of unique sociocultural experiences. The limitations of this meta-analysis and future directions for stress research with various ethnic groups are discussed. Statement of contribution What is already known on this subject? Studies have found vast health disparities among ethnic groups. Psychological and physiological illnesses and atypical diurnal cortisol profiles are strongly correlated. Studies have examined the relationship between diurnal cortisol rhythms and ethnicity, but findings are mixed. What does this study add? This study is a systematic examination of the relationship between diurnal cortisol rhythm and ethnicity. Psychosocial and methodological factors moderate the relationship between diurnal cortisol output and ethnicity. This study provides insight on factors that contribute to health disparities among ethnic groups.

Stress reactivity in healthy child offspring of parents with anxiety disorders.

Several studies suggest that anxiety disorders (AD) involve dysregulation of the autonomic nervous system (ANS) and hypothalamic-pituitary (HPA) axis. However, it is unknown if alterations in these biological systems are premorbid markers of AD risk or a state-dependent feature of anxiety. This study examined ANS and HPA-axis response to a laboratory stressor in healthy child offspring of parents with (n = 55) and without (n = 98) a history of AD. High frequency heart rate variability (HF-HRV) was assessed during sitting and standing baseline conditions and during a speech task where participants remained standing. Salivary cortisol was measured at baseline and at 15, 30, 45 and 60 min post-speech. Subjective anxiety was assessed with a visual analogue scale. Children of parents with AD displayed reduced HRV and a blunted cortisol response to the speech task compared to children of non-anxious parents. No risk group effect was found for anxiety ratings. These preliminary data suggest that healthy children of anxious parents exhibit altered stress reactivity to an acute laboratory stressor. Further research is needed to confirm findings and identify mechanisms that may account for altered self-regulation processes to a stressor in children at familial risk for AD.

Salivary secretory immunoglobulin A reactivity: a comparison to cortisol and α-amylase patterns in the same breast cancer survivors.

INTRODUCTION: One way to examine the extent to which the stress associated with a breast cancer experience (BC) impacts stress-related physiological mechanisms is to study the secretion patterns of associated biomarkers. Unlike cortisol and α-amylase (sAA), biomarkers of immune functioning such as secretory immunoglobulin A (SIgA) have rarely been examined in BC survivors. AIM OF THE STUDY: This study had two principal aims: the first was to evaluate the basal secretion profiles of SIgA as well as its response to an acute stressor as a marker of immune health in BC survivors and women with no history of BC, and the second was to determine how SIgA stress-related patterns compare to published cortisol and sAA patterns in the same women. RESULTS: Overall, the findings indicate that BC survivors exhibit a blunted cortisol reaction to an acute stressor, a generally elevated diurnal sAA concentration pattern, and normal SIgA profiles, compared to women with no history of cancer. This study serves as a foundation for future research to elucidate the relationships between BC experience variables, stress biomarkers, and health outcomes in BC survivors.

Assessment of executive function using the Tinkertoy test.

The Tinkertoy test (TTT) has often been used to assess executive function. Despite its clinical importance, there are few published normative data for it. Thus, the primary aim of this study was to fill this gap. Moreover, as there exists a sex difference in many cognitive abilities and neuropsychological tests, a secondary aim was to examine whether sex influences TTT performance. We administered the TTT to 25 healthy men and 25 healthy women whose average age was 28 years. Performances were scored based upon Lezak's (1982) original TTT criteria. On average, our participants used 43 pieces to complete their construction (SD=8), with a range of 21-50, and their complexity scores ranged from 7 to 12, with a mean score of 9.68 (SD=1.35). Overall performance did not differ based on sex; yet, when examining individual scoring criteria, we found that men scored significantly higher on the symmetry measure. Efforts towards the development of adequate normative data for the TTT and different tests of executive functioning are crucial to neuropsychologists' and other healthcare providers' ability to reliably diagnose and treat disorders of cognition that affect executive function. The present data go some way towards enhancing the utility of the TTT.

Cancer-related cognitive impairment in breast cancer survivors: An examination of conceptual and statistical cognitive domains using principal component analysis.

There is a great deal of variability in the composition of neuropsychological test batteries used in the assessment of cancerrelated cognitive impairment (CRCI). Not only the development of a gold standard approach for CRCI assessment would allow for easier identification of women suffering from CRCI but it would also promote optimal care for survivors. As a first step towards the development of a valid and reliable unified test battery, the objective of this study was to verify whether the theoretical domains commonly used in CRCI assessment are statistically supported, before and after breast cancer treatment. Principal component analyses (PCA) were performed on the results from 23 neuropsychological tests grouped into eight conceptual domains. For baseline data, the Kaiser-Meyer-Olkin was .82 and Bartlett's X2(253, N=95) = 949.48, P<0.001. A five-component solution explained 60.94% of the common variance. For the post-treatment data, the Kaiser-Meyer-Olkin was .83 and Bartlett's X2(253, N=95) = 1007.21, P<0.001 and a five component solution explained 62.03% of the common variance. Although a visual comparison of the theoretical model with those determined via PCA indicated important overlap between conceptual domains and statistical components, significant dissimilarities were also observed.

Effects of combined pre- and post-natal enrichment on anxiety-like, social, and cognitive behaviours in juvenile and adult rat offspring.

The pre- and post-natal periods are characterized by unrivalled growth and are sensitive to environmental changes. A correctly stimulating early environment is essential for developing natural behaviors and maintaining affective wellness. Five litters of rat progeny were co-housed through gestation until juvenile age in housing providing physical and social enrichment. Five control litters were housed separately in standard conditions. Half of the offspring were tested in the elevated plus-maze and the social interaction test as juveniles (five weeks old) with the other half tested in the Morris water maze. As adults (11 weeks old), the testing groups were reversed. Weight was monitored weekly. Enriched offspring had leaner body weights. In the elevated plus-maze, control juvenile progeny spent a higher percentage of time in the open arms, showed greater locomotor activity, less grooming, and more rearing (males only). In the social interaction test, enriched juvenile offspring were found to sniff their conspecific more, display more self-grooming behaviour as well as show less locomotor activity and body contact. In the Morris water maze probe test, enriched rats demonstrated improved memory for the platform position and more effective search strategies with increased platform crossings, middle crossing as well as more time spent in the platform quadrant and less thigmotaxis behaviour. Adult female rat offspring also demonstrated superior memory for the platform position and crossed the maze middle more often. These results suggest that combined pre- and post-natal environmental enrichment influences physiology and behaviour in offspring rats with some of those influences being long-lasting.

The role of stressful life events on the cortisol reactivity patterns of breast cancer survivors.

OBJECTIVE: Atypical patterns of cortisol secretion following an acute stressor have been commonly reported in breast cancer survivors. Stressful life events have been associated with blunted acute cortisol levels in other populations. The purpose of this study was to explore the role of stressful life events on cortisol secretion patterns of breast cancer survivors following an acute stressor. DESIGN: The Trier Social Stress (TSST) was used to elicit a moderate stress response in breast cancer survivors (n = 19) and a control group (n = 17). Saliva samples were collected before, during and after the TSST to provide cortisol concentrations. During recovery, we recorded the frequency and subjective impact of stressful life events in the past year using the Life Experience Survey. RESULTS: Simple regressions analyses were performed; results suggest no group differences between the total number of stressful life events and their subjective impact. However, the total number of stressful life events as well as their subjective impact correlated negatively with the peak cortisol concentration in breast cancer survivors. CONCLUSIONS: The cumulative effect of stressful life events, positive and negative, may impact the endocrine stress system of breast cancer survivors more so than that of women with no history of cancer.

Strain Differences and Effects of Environmental Manipulation on Astrocytes (Glial Fibrillary Acidic Protein), Glucocorticoid Receptor, and Microglia (Iba1) Immunoreactivity between Wistar-Kyoto and Wistar Females.

BACKGROUND: Depression is often associated with an increase in hypothalamic-pituitary-adrenal (HPA) axis reactivity and immune response. To investigate this relationship, we examined the consequences of environmental manipulation on the neural correlates of the HPA axis and immune response in an animal model of depression, the Wistar-Kyoto (WKY) rat. Additionally, female animals are often overlooked in preclinical research because of the hormone fluctuations inherent in the estrous cycle. METHODS: Female rats were randomly assigned to 1 of 3 environments for 30 days: (1) environmental enrichment (EE), (2) standard housing (SH), and (3) isolated housing (IH). Immunoreactivity of astrocytes (glial fibrillary acidic protein [GFAP]), glucocorticoid receptors (GRs), and microglia (Iba1) in the hippocampus and amygdala were measured using immunohistochemistry. RESULTS: WKY animals had significantly more GR staining area and Iba1 staining intensity and area in the CA1 of the hippocampus. In enriched Wistar rats, GFAP staining intensity and area were greater in the CA1. A trend towards a greater percent of area stained with GR was found in WKY animals as compared to that of the Wistar animals. This was due to WKY females in EE having significantly higher GR staining intensity and area in the amygdala as compared to that of animals in SH. DISCUSSION: These strain differences lend support to the use of WKY animals as an animal model of depression. Furthermore, due to the effects of EE on GFAP and GR staining in WKY females, we suggest that EE can be used as an intervention to potentially alleviate the negative effects of depression.

Corticosterone and immune cytokine characterization following environmental manipulation in female WKY rats.

This study investigated the effects of environmental manipulation on female Wistar Kyoto (WKY), an animal model of depression, and female Wistar rats. It explored the function of the hypothalamic-pituitary-adrenal axis (HPA) and immune system, as they have both been implicated in the pathophysiology of depression. A further goal was to characterize the immune cytokine concentrations of female WKY rats as this has, to our knowledge, never been documented. Animals were assigned to enriched, standard, or impoverished housing for four consecutive weeks. Following this, serum was collected at baseline and post-stress periods to measure the concentration of corticosterone, TNF-α, IL-1ß, and IL-10. WKY animals had significantly higher corticosterone levels at the post-stress time-point than their Wistar counterparts. WKY females in isolation tended to have the lowest corticosterone levels which may indicate that they prefer a solitary environment, a symptom of depression. We observed a significant decrease in TNF-α after enrichment in the Wistar strain. A similar decrease in TNF-α was found in the WKY strain, but there was no difference between environmental conditions. There was a significant increase in pre- to post-stress IL-10 level in both Wistar and WKY animals. WKY females had a significantly lower level of IL-1ß as compared to the Wistar animals at both pre- and post-stress time points. Given this strain difference, it is likely that the WKY rats had a dysregulated HPA axis which further influenced their circulating cytokine levels. Further studies are needed to examine how this pattern of findings plays a role in the pathophysiology of depression.

The Effects of Outgroup Threat and Opportunity to Derogate on Salivary Cortisol Levels.

Perceptions of intergroup threat have been related to both experiences of physiological stress responses and derogation of the outgroup. In this study, a neuroscience perspective was used to investigate the relationship between stress and opportunity to derogate the outgroup, in a threatening intergroup context. Research from a social identity perspective suggests that engaging in outgroup derogation alleviates stress when perceiving an intergroup threat. However, in line with the model of intergroup anxiety, opportunity to derogate could exacerbate the negative connotations of a threatening situation, resulting in more stress. Canadian participants (N = 110) were exposed to text describing either discriminatory or favorable comments expressed by Chinese individuals towards Canadians. Half of the participants were given the opportunity to derogate via a bias task. Salivary cortisol was used as a measure of stress and was collected at baseline, post-threat, and post-derogation. As expected, threatening identity led to more stress as evidenced by increased cortisol concentrations. Furthermore, threatened participants who had an opportunity to derogate showed greater cortisol concentrations than those who did not. These results demonstrate a link between stress and the opportunity to derogate, and highlights the value of using biological markers within the intergroup context. Rewrite abstract to remove all the references (they are meaningless because the abstracting services will use the abstract as is but will not provide the references so their presence is useless.

Salivary Alpha-Amylase Reactivity in Breast Cancer Survivors.

The two main components of the stress system are the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes. While cortisol has been commonly used as a biomarker of HPA functioning, much less attention has been paid to the role of the SAM in this context. Studies have shown that long-term breast cancer survivors display abnormal reactive cortisol patterns, suggesting a dysregulation of their HPA axis. To fully understand the integrity of the stress response in this population, this paper explored the diurnal and acute alpha-amylase profiles of 22 breast cancer survivors and 26 women with no history of cancer. Results revealed that breast cancer survivors displayed identical but elevated patterns of alpha-amylase concentrations in both diurnal and acute profiles relative to that of healthy women, F (1, 39) = 17.95, p < 0.001 and F (1, 37) = 7.29, p = 0.010, respectively. The average area under the curve for the diurnal and reactive profiles was 631.54 ± 66.94 SEM and 1238.78 ± 111.84 SEM, respectively. This is in sharp contrast to their cortisol results, which showed normal diurnal and blunted acute patterns. The complexity of the stress system necessitates further investigation to understand the synergistic relationship of the HPA and SAM axes.

Environmental manipulation affects depressive-like behaviours in female Wistar-Kyoto rats.

While the efficacy of pharmacological interventions to treat depression has been well-studied in animal models, much less work has been done to shed light on how changes in the immediate environment can impact behaviour. Furthermore, most studies have focused on male rodents despite the prevalence of mood disorders in women. In this study, 36 Wistar Kyoto (validated animal model of depression) and 36 Wistar (control) female rats were used to examine the effects of environmental manipulation on depressive- and anxiety-like behaviours. Animals were assigned to one of three groups: standard (3 rats/cage), enriched (6 rats/cage plus physical enrichment), and isolation (1 rat/cage) housing. The elevated plus maze (EPM) and forced swim test (FST) were conducted prior to, and four weeks after environmental assignment to measure anxiety-like and depressive-like behaviours, respectively. Sucrose preference assessed anhedonia both before and after environmental assignment. Weight was measured every week to monitor weight-gain over time. Post-environment sucrose preference was significantly increased in animals in enriched housing as compared to those in isolated housing in both strains. While there were significant differences between strains in measures of open arm duration in the EPM and immobility in the FST, there appeared to be no differences between environmental groups. The results of this study highlight the importance of environmental factors in the expression of anhedonia. Enrichment appears to reduce anhedonia while isolation increases anhedonia. These effects should be studied further to assess whether longer periods of social and physical enrichment alleviate other symptoms of depression.

In utero programming alters adult response to chronic mild stress: part 3 of a longitudinal study.

Exposure to stress before birth may lay the foundation for the development of sensitivities or protection from psychiatric disorders while later stress exposure may trigger either their expression or suppression. This report, part three of a longitudinal study conducted in our laboratory, aimed to examine the interaction between early and adult stress and their effects on measures of anxiety and depression. In parts one and two, we reported the effects of gestational stress (GS) in Long Evans rat dams and their juvenile and young adult offspring. In this third and final installment, we evaluated the effects of GS and chronic mild stress (CMS) in the adult female offspring at 6 month and 12 month time-points. The two by two design included a combination of GS and CMS and the appropriate control groups. Using Hierarchical Linear Modeling, main effects of GS on corticosterone level at the 12 month time-point was found while main effects of CMS were seen in body weight, sucrose preference, and corticosterone, and significant interactions between group at the 6 and 12 month time-points. The GS group had the lowest sucrose preference during CMS at 6 months supporting a cumulative effect of early and later life stress. The GS/CMS group showed lower corticosterone at 12 months than the GS/noCMS group indicating a possible mismatch between prenatal programming and later life stress. These results highlight the importance of early life factors in exerting potentially protective effects in models involving later life stress.

Bisphenol-A: epigenetic reprogramming and effects on reproduction and behavior.

Bisphenol A (BPA) is a synthetic compound used in the production of many polycarbonate plastics and epoxy resins. It is one of the most widely produced chemicals in the world today and is found in most canned goods, plastics, and even household dust. Exposure to BPA is almost universal: most people have measurable amounts of BPA in both urine and serum. BPA is similar in structure to estradiol and can bind to multiple targets both inside and outside the nucleus, in effect acting as an endocrine disruptor. Research on BPA exposure has accelerated in the past decade with findings suggesting that perinatal exposure to BPA can negatively impact both male and female reproduction, create alterations in behavior, and act as a carcinogen. BPA can have both short term and long term effects with the latter typically occurring through epigenetic mechanisms such as DNA methylation. This review will draw on both human and animal studies in an attempt to synthesize the literature and examine the effects of BPA exposure on reproduction, behavior, and carcinogenesis with a focus on the potential epigenetic mechanisms by which it acts.

The impact of motherhood on perceived stress, illness intrusiveness and fear of cancer recurrence in young breast cancer survivors over time.

OBJECTIVE: Parenting while coping with breast cancer can be challenging for many young women, yet little is known about the impact of motherhood on their well-being over time. DESIGN: The first part of this study examined differences in perceived stress, illness intrusiveness and fear of cancer recurrence between young breast cancer survivors with and without children in two separate time frames (0-5 and 5-15 years since diagnosis). The second part identified determinants for these elements of well-being in young mothers exclusively. MAIN OUTCOME MEASURES: Seven hundred and forty two young North American women previously diagnosed with breast cancer completed measures of perceived stress, illness intrusiveness, fear of cancer recurrence and parenting stress (mothers only) via a web-based survey. RESULTS: Compared to young survivors without children, young mothers reported higher levels of fear of cancer recurrence and illness intrusiveness in intimate life domains during both time frames. Part 2 revealed how maternal age, age of children, time since diagnosis and parenting stress impacted on well-being in this group. CONCLUSIONS: Young mothers with breast cancer need support to manage their fears of having a recurrence and to cope with problems in intimacy well into remission. This study identifies the most vulnerable groups of mothers.

Young and worried: Age and fear of recurrence in breast cancer survivors.

OBJECTIVE: Fear of cancer recurrence (FCR) is a frequently cited and unmet need of cancer survivors. While the relation between age and FCR is well documented, the mechanisms that may explain this phenomenon remain to be investigated. This study examined four possible mechanisms of the relation between age and FCR: motherhood, severity of the cancer (defined as cancer stage and chemotherapy), anxiety, and illness intrusiveness. METHODS: 3,239 women with breast cancer (mean time since diagnosis: 6.6 years) completed the Concerns About Recurrence Scale (CARS), the State Trait Anxiety Inventory (STAI), and the Illness Intrusiveness Ratings Scale (IIRS) within a larger web-based study. Women were divided into four groups based on their current age: < 34, 35-49, 50-64, and >65. Multivariate analyses were performed with age category and motherhood as the independent variables and the CARS subscales as the dependent variables, controlling for age of children and relevant covariates. Severity of the cancer, anxiety, and illness intrusiveness were simultaneously tested as mediators of the relation between age and FCR. RESULTS: Results indicated that age category was related to FCR, F = 10.37, p < .001. Follow-up tests revealed that women under 34 or 35-49 expressed the highest levels of FCR. Mothers, regardless of their ages or the ages of their children, expressed greater FCR. Illness intrusiveness and to a lesser extent anxiety were mediators of the relation between age and FCR, while severity of the cancer was not. CONCLUSIONS: Younger age was associated with more FCR among breast cancer patients, regardless of motherhood status. Our findings suggest new, potentially valuable ways of managing FCR by helping affected people to reduce anxiety and illness intrusiveness.

Differences in verbal memory retrieval in breast cancer chemotherapy patients compared to healthy controls: a prospective fMRI study.

Cognitive complaints by breast cancer survivors receiving chemotherapy have led to an increasing interest in elucidating the possible causes of such impairment. Although a number of neuroimaging studies have been conducted, only a handful of them have taken into account cognitive status pre-chemotherapy. The current study included pre-chemotherapy and post-chemotherapy assessment. In addition, various factors such as depression, anxiety, fatigue and days since surgery were considered during analyses. Breast cancer patients performed an fMRI verbal recall task before and an average of 1 month after chemotherapy. Well matched controls also performed the task with a similar timeline. Pre-chemotherapy analyses revealed that patients activated the anterior cingulate less than controls during memory retrieval when anxiety and fatigue scores were added as covariates during group comparisons. In addition, there were also changes in brain activation from pre- to post-chemotherapy in patients but not in controls. Post-chemotherapy, patients had less activation in the bilateral insula, the left inferior orbitofrontal cortex and the left middle temporal gyrus. Finally, patients also showed significantly less activation when compared to controls. Brain regions included: the right middle and superior temporal gyrus, the right medial frontal gyrus, the right inferior orbitofrontal cortex, the left insula and left superior temporal pole. Importantly, depression, anxiety, and particularly fatigue accounted for some of brain activation differences. Our results suggest that chemotherapy in part plays a role in brain activation differences and it also highlights the importance of rigorously controlling for confounding variables. Only by controlling such factors can we understand the role that chemotherapy may play on cognition.

Prechemotherapy differences in response inhibition in breast cancer patients compared to controls: a functional magnetic resonance imaging study.

Prechemotherapy neuroimaging data are lacking in posttreatment cognitive impairment studies. Breast cancer patients and noncancer controls were scanned prior to chemotherapy during a response inhibition task. Task reaction times and error rates, as well as neuropsychological tests, hospital records, and salivary biomarkers, were investigated, yielding no significant group differences. Significant group differences observed for the functional magnetic resonance imaging (fMRI) data depended on the type of analysis performed, most consistently implicating widespread attenuated activations in patients. The patient group also revealed considerable variability in task-related brain activity. These pretreatment differences highlight the need to understand the effects of confounding variables before considering posttreatment effects. Role of the funding source: The Canadian Breast Cancer Foundation has funded this project. Their contribution was solely financial support.

Pre-chemotherapy differences in visuospatial working memory in breast cancer patients compared to controls: an FMRI study.

INTRODUCTION: Cognitive deficits are a side-effect of chemotherapy, however pre-treatment research is limited. This study examines neurofunctional differences during working memory between breast cancer (BC) patients and controls, prior to chemotherapy. METHODS: Early stage BC females (23), scanned after surgery but before chemotherapy, were individually matched to non-cancer controls. Participants underwent functional magnetic resonance imaging (fMRI) while performing a Visuospatial N-back task and data was analyzed by multiple group comparisons. fMRI task performance, neuropsychological tests, hospital records, and salivary biomarkers were also collected. RESULTS: There were no significant group differences on neuropsychological tests, estrogen, or cortisol. Patients made significantly fewer commission errors but had less overall correct responses and were slower than controls during the task. Significant group differences were observed for the fMRI data, yet results depended on the type of analysis. BC patients presented with increased activations during working memory compared to controls in areas such as the inferior frontal gyrus, insula, thalamus, and midbrain. Individual group regressions revealed a reverse relationship between brain activity and commission errors. CONCLUSION: This is the first fMRI investigation to reveal neurophysiological differences during visuospatial working memory between BC patients pre-chemotherapy and controls. These results also increase the knowledge about the effects of BC and related factors on the working memory network. SIGNIFICANCE: This highlights the need to better understand the pre-chemotherapy BC patient and the effects of associated confounding variables.

Environmental-enrichment-related variations in behavioral, biochemical, and physiologic responses of Sprague-Dawley and Long Evans rats.

The behavioral, biochemical, and physiologic consequences of 6 wk of environmental enrichment were evaluated in male Long Evans and Sprague-Dawley rats and compared with those of rats in standard single-housing conditions. Standard housing provided little or no social or physical stimulation whereas environmental enrichment comprised group housing for 8 h daily in a 3-story cage equipped with novel stimuli. Dependent measures included performance in the forced swim test, thresholds for brain-stimulation reward, sucrose intake and preference, determination of corticosterone levels before and after brief restraint stress, and rate of weight gain. In forced swimming tests, active behaviors (diving, swimming with struggling, and climbing) tended to dominate over passive behaviors (sinking, floating) in both groups and outbred rat stocks (especially in enriched groups) on the first day. These behaviors were replaced with maintenance behaviors such as grooming and swimming without struggling on the second exposure, with enriched Long Evans rats showing the largest decline in activity. Baseline plasma corticosterone levels were elevated in both rat stocks after 6 wk of enrichment. After restraint stress, hormone levels in enriched animals tended to peak earlier and approach or exceed baseline values more quickly than was observed in the comparable control groups. Rate of body weight gain was greater in enriched Long Evans rats than Sprague-Dawley or control rats. Our observations indicate that stock- and group-associated differences in several indices occur in association with enrichment. The data support the claim that environmental enrichment may render animals more resilient to challenges.