Allostasis: a neural behavioral perspective

Ghrelin is associated with an elevated mood after an overnight fast in depression

BACKGROUND

Major depressive disorder (MDD) comprises subtypes with distinct symptom profiles. For example, patients with melancholic and atypical MDD differ in the direction of appetite and body weight changes as well as mood reactivity. Despite reported links to altered energy metabolism, the role of circulating neuropeptides from the gut in modulating such symptoms remains largely elusive.

METHODS

We collected data from 103 participants, including 52 patients with MDD and 51 healthy control participants (HCP). After an overnight fast, we measured plasma levels of (acyl and des-acyl) ghrelin and participants reported their current metabolic and mood states using visual analog scales (VAS). Furthermore, they completed symptom-related questionnaires (i.e., STAI-T).

RESULTS

Patients with atypical versus melancholic MDD reported less negative affect (p = 0.025). Higher levels of acyl ghrelin (corrected for BMI) were associated with improved mood (p = 0.012), specifically in patients with MDD. These associations of ghrelin were not mood-item specific and exceeded correlations with trait markers of negative affectivity. In contrast to associations with mood state, higher levels of ghrelin were not associated with increased hunger per se or changes in appetite in patients with MDD.

LIMITATIONS

The study is limited by the cross-sectional design without an intervention.

CONCLUSIONS

Our results reveal potentially mood-enhancing effects of ghrelin in fasting individuals that exceed associations with metabolic state ratings. These associations with circulating neuropeptides might help explain anti-depressive effects of fasting interventions and could complement conventional treatments in patients with melancholic MDD.

The application of allostasis and allostatic load in animal species: A scoping review

Principles of allostasis and allostatic load have been widely applied in human research to assess the impacts of chronic stress on physiological dysregulation. Over the last few decades, researchers have also applied these concepts to non-human animals. However, there is a lack of uniformity in how the concept of allostasis is described and assessed in animals. The objectives of this review were to: 1) describe the extent to which the concepts of allostasis and allostatic load are applied theoretically to animals, with a focus on which taxa and species are represented; 2) identify when direct assessments of allostasis or allostatic load are made, which species and contexts are represented, what biomarkers are used, and if an allostatic load index was constructed; and 3) detect gaps in the literature and identify areas for future research. A search was conducted using CABI, PubMed, Agricola, and BIOSIS databases, in addition to a complementary hand-search of 14 peer-reviewed journals. Search results were screened, and articles that included non-human animals, as well as the terms “allostasis” or “allostatic” in the full text, were included. A total of 572 articles met the inclusion criteria (108 reviews and 464 peer-reviewed original research). Species were represented across all taxa. A subset of 63 publications made direct assessments of allostatic load. Glucocorticoids were the most commonly used biomarker, and were the only biomarker measured in 25 publications. Only six of 63 publications (9.5%) constructed an allostatic load index, which is the preferred methodology in human research. Although concepts of allostasis and allostatic load are being applied broadly across animal species, most publications use single biomarkers that are more likely indicative of short-term rather than chronic stress. Researchers are encouraged to adopt methodologies used in human research, including the construction of species-specific allostatic load indexes.

Neurophysiological Perspective on Allostasis and Homeostasis: Dynamic Adaptation in Viable Systems

Allostasis is a physiological principle based on a dynamic regulatory system, contrary to homeostasis, in which the goal is to reach a steady state and recover from deviation from a set point in the internal environment. The concept of allostasis has continued to develop with advances in the field of neuroscience. In this short review, the author presents several new findings in neuroscience and extend the concept of allostasis as mutual regulation between cognitive, somatic, and autonomic systems. In this manner, biological systems adapt to external and internal environments by changing themselves.

Physical Activity Influences Cortisol and Dehydroepiandrosterone (Sulfate) Levels in Older Adults: A Systematic Review and Meta-Analysis

Age-related changes affect the ratio between two steroid hormones of the hypothalamic-pituitary-adrenal axis, cortisol and dehydroepiandrosterone (sulfate) (DHEA[S]). Physical activity (PA) may buffer the effects of chronic stress and counteract the aging decline of DHEA(S). Therefore, a systematic review was conducted to understand how PA influences physiological markers of cortisol and/or DHEA(S) and whether there is a difference in observational associations or experimental effects in older adults aged 65 years and older. A narrative synthesis was performed on nine observational studies, and meta-analyses were performed on 22 randomized controlled trials. There was low- to moderate-quality evidence that regular PA beneficially reduces cortisol and increases DHEA(S) levels. Subgroup analyses showed no clinically important differences between men and women, different exercise modalities, or health states. The findings cautiously suggest that regular PA of older adults' own choice that they find enjoyable could be recommended to improve cortisol and/or DHEA(S) levels.

Neuronal metabolism in learning and memory: The anticipatory activity perspective

Current research on the molecular mechanisms of learning and memory is based on the "stimulus-response" paradigm, in which the neural circuits connecting environmental events with behavioral responses are strengthened. By contrast, cognitive and systems neuroscience emphasize the intrinsic activity of the brain that integrates information, establishes anticipatory actions, executes adaptive actions, and assesses the outcome via regulatory feedback mechanisms. We believe that the difference in the perspectives of systems and molecular studies is a major roadblock to further progress toward understanding the mechanisms of learning and memory. Here, we briefly overview the current studies in molecular mechanisms of learning and memory and propose that studying the predictive properties of neuronal metabolism will significantly advance our knowledge of how intrinsic, predictive activity of neurons shapes a new learning event. We further suggest that predictive metabolic changes in the brain may also take place in non-neuronal cells, including those of peripheral tissues. Finally, we present a path forward toward more in-depth studies of the role of cell metabolism in learning and memory.

Biological Prescience: The Role of Anticipation in Organismal Processes

Anticipation is the act of using information about the past and present to make predictions about future scenarios. As a concept, it is predominantly associated with the psychology of the human mind; however, there is accumulating evidence that diverse taxa without complex neural systems, and even biochemical networks themselves, can respond to perceived future conditions. Although anticipatory processes, such as circadian rhythms, stress priming, and cephalic responses, have been extensively studied over the last three centuries, newer research on anticipatory genetic networks in microbial species shows that anticipatory processes are widespread, evolutionarily old, and not simply reserved for neurological complex organisms. Overall, data suggest that anticipatory responses represent a unique type of biological processes that can be distinguished based on their organizational properties and mechanisms. Unfortunately, an empirically based biologically explicit framework for describing anticipatory processes does not currently exist. This review attempts to fill this void by discussing the existing examples of anticipatory processes in non-cognitive organisms, providing potential criteria for defining anticipatory processes, as well as their putative mechanisms, and drawing attention to the often-overlooked role of anticipation in the evolution of physiological systems. Ultimately, a case is made for incorporating an anticipatory framework into the existing physiological paradigm to advance our understanding of complex biological processes.

Stress hypothesis overload: 131 hypotheses exploring the role of stress in tradeoffs, transitions, and health

Stress is ubiquitous and thus, not surprisingly, many hypotheses and models have been created to better study the role stress plays in life. Stress spans fields and is found in the literature of biology, psychology, psychophysiology, sociology, economics, and medicine, just to name a few. Stress, and the hypothalamic-pituitaryadrenal/interrenal (HPA/I) axis and sympathetic nervous system (SNS), are involved in a multitude of behaviors and physiological processes, including life-history and ecological tradeoffs, developmental transitions, health, and survival. The goal of this review is to highlight and summarize the large number of available hypotheses and models, to aid in comparative and interdisciplinary thinking, and to increase reproducibility by a) discouraging hypothesizing after results are known (HARKing) and b) encouraging a priori hypothesis testing. For this review I collected 214 published hypotheses or models dealing broadly with stress. In the main paper, I summarized and categorized 131 of those hypotheses and models which made direct connections among stress and/or HPA/I and SNS, tradeoffs, transitions, and health. Of those 131, the majority made predictions about reproduction (n = 43), the transition from health to disease (n = 38), development (n = 23), and stress coping (n = 18). Additional hypotheses were classified as stage-spanning or models (n = 37). The additional 83 hypotheses found during searches were tangentially related, or pertained to immune function or oxidative stress, and these are listed separately. Many of the hypotheses share underlying rationale and suggest similar, if not identical, predictions, and are thus not mutually exclusive; some hypotheses spanned classification categories. Some of the hypotheses have been tested multiple times, whereas others have only been examined a few times. It is the hope that multi-disciplinary stress researchers will begin to harmonize their naming of hypotheses in the literature so as to build a clearer picture of how stress impacts various outcomes across fields. The paper concludes with some considerations and recommendations for robust testing of stress hypotheses.

Allostasis: A Brain-Centered, Predictive Mode of Physiological Regulation

Although the concept of allostasis was proposed some 30 years ago, doubts persist about its precise meaning and whether it is useful. Here we review the concept in the context of recent studies as a strategy to efficiently regulate physiology and behavior. The brain, sensing the internal and external milieu, and consulting its database, predicts what is likely to be needed; then, it computes the best response. The brain rewards a better-than-predicted result with a pulse of dopamine, thereby encouraging the organism to learn effective regulatory behaviors. The brain, by prioritizing behaviors and dynamically adjusting the flows of energy and nutrients, reduces costly errors and exploits more opportunities. Despite significant costs of computation, allostasis pays off and can now be recognized as a core principle of organismal design.

A New Integrative Theory of Brain-Body-Ecosystem Medicine: From the Hippocratic Holistic View of Medicine to Our Modern Society

Humans are increasingly aware that their fate will depend on the wisdom they apply in interacting with the ecosystem. Its health is defined as the condition in which the ecosystem can deliver and continuously renew its fundamental services. A healthy ecosystem allows optimal interactions between humans and the other biotic/abiotic components, and only in a healthy ecosystem can humans survive and efficiently reproduce. Thus, both the human and ecosystem health should be considered together in view of their interdependence. The present article suggests that this relationship could be considered starting from the Hippocrates (460 BC-370 BC) work "On Airs, Waters, and Places" to derive useful medical and philosophical implications for medicine which is indeed a topic that involves scientific as well as philosophical concepts that implicate a background broader than the human body. The brain-body-ecosystem medicine is proposed as a new more complete approach to safeguarding human health. Epidemiological data demonstrate that exploitation of the environment resulting in ecosystem damage affects human health and in several instances these diseases can be detected by modifications in the heart-brain interactions that can be diagnosed through the analysis of changes in heart rate variability.

Sex × Gender and Sexual Orientation in Relation to Stress Hormones and Allostatic Load

In this selective review, emerging literature linking biological sex, sociocultural gender, and sexual orientation to stress hormone functioning and multisystemic physiological dysregulations are summarized. Beyond sex as a binary biological variable, continuums of sex hormones, gender roles, gender identity, and sexual orientation each uniquely help delineate pathways and mechanisms linked to stress-related disease trajectories. This implicates glucocorticoid functioning and allostatic load, the “wear and tear” of chronic stress in synergy with unhealthy behaviors. Clinical considerations are also discussed for the field of gender medicine.

Socioeconomically Disadvantaged Adolescents with Elevated Externalizing Symptoms Show Heightened Emotion Reactivity to Daily Stress: An Experience Sampling Study

Numerous theories assert that youth with externalizing symptomatology experience intensified emotion reactivity to stressful events; yet scant empirical research has assessed this notion. Using in-vivo data collected via experience sampling methodology, we assessed whether externalizing symptoms conditioned adolescents' emotion reactivity to daily stressors (i.e. change in emotion pre-post stressor) among 206 socioeconomically disadvantaged adolescents. We also assessed whether higher externalizing symptomology was associated with experiencing more stressors overall, and whether adolescents' emotional upheavals resulted in experiencing a subsequent stressor. Hierarchical linear models showed that adolescents higher in externalizing symptoms experienced stronger emotion reactivity in sadness, anger, jealously, loneliness, and (dips in) excitement. Externalizing symptomatology was not associated with more stressful events, but a stress-preventative effect was found for recent upheavals in jealousy among youth low in externalizing. Findings pinpoint intense emotion reactivity to daily stress as a risk factor for youth with externalizing symptoms living in socioeconomic disadvantage.

A Comprehensive Overview on Stress Neurobiology: Basic Concepts and Clinical Implications

Stress is recognized as an important issue in basic and clinical neuroscience research, based upon the founding historical studies by Walter Canon and Hans Selye in the past century, when the concept of stress emerged in a biological and adaptive perspective. A lot of research after that period has expanded the knowledge in the stress field. Since then, it was discovered that the response to stressful stimuli is elaborated and triggered by the, now known, stress system, which integrates a wide diversity of brain structures that, collectively, are able to detect events and interpret them as real or potential threats. However, different types of stressors engage different brain networks, requiring a fine-tuned functional neuroanatomical processing. This integration of information from the stressor itself may result in a rapid activation of the Sympathetic-Adreno-Medullar (SAM) axis and the Hypothalamus-Pituitary-Adrenal (HPA) axis, the two major components involved in the stress response. The complexity of the stress response is not restricted to neuroanatomy or to SAM and HPA axes mediators, but also diverge according to timing and duration of stressor exposure, as well as its short- and/or long-term consequences. The identification of neuronal circuits of stress, as well as their interaction with mediator molecules over time is critical, not only for understanding the physiological stress responses, but also to understand their implications on mental health.

Hair and Salivary Testosterone, Hair Cortisol, and Externalizing Behaviors in Adolescents

Although testosterone is associated with aggression in the popular imagination, previous research on the links between testosterone and human aggression has been inconsistent. This inconsistency might be because testosterone's effects on aggression depend on other moderators. In a large adolescent sample ( N = 984, of whom 460 provided hair samples), we examined associations between aggression and salivary testosterone, hair testosterone, and hair cortisol. Callous-unemotional traits, parental monitoring, and peer environment were examined as potential moderators of hormone-behavior associations. Salivary testosterone was not associated with aggression. Hair testosterone significantly predicted increased aggression, particularly at low levels of hair cortisol (i.e., Testosterone × Cortisol interaction). This study is the first to examine the relationship between hair hormones and externalizing behaviors and adds to the growing literature that indicates that androgenic effects on human behavior are contingent on aspects of the broader endocrine environment-in particular, levels of cortisol.

Dominant and opponent relations in cortical function: An EEG study of exam performance and stress

This paper analyzes the opponent dynamics of human motivational and affective processes, as conceptualized by RS Solomon, from the position of AA Ukhtomsky's neurophysiological principle of the dominant and its applications in the field of human electroencephalographic analysis. As an experimental model, we investigate the dynamics of cortical activity in students submitting university final course oral examinations in naturalistic settings, and show that successful performance in these settings depends on the presence of specific types of cortical activation patterns, involving high indices of left-hemispheric and frontal cortical dominance, whereas the lack thereof predicts poor performance on the task, and seems to be associated with difficulties in the executive regulation of cognitive (intellectual) and motivational processes in these highly demanding and stressful conditions. Based on such knowledge, improved educational and therapeutic interventions can be suggested which take into account individual variability in the neurocognitive mechanisms underlying adaptation to motivationally and intellectually challenging, stressful tasks, such as oral university exams. Some implications of this research for opponent-process theory and its closer integration into current neuroscience research on acquired motivations are discussed.

Social connectedness is associated with fibrinogen level in a human social network

Socially isolated individuals face elevated rates of illness and death. Conventional measures of social connectedness reflect an individual's perceived network and can be subject to bias and variation in reporting. In this study of a large human social network, we find that greater indegree, a sociocentric measure of friendship and familial ties identified by a subject's social connections rather than by the subject, predicts significantly lower concentrations of fibrinogen (a biomarker of inflammation and cardiac risk), after adjusting for demographics, education, medical history and known predictors of cardiac risk. The association between fibrinogen and social isolation, as measured by low indegree, is comparable to the effect of smoking, and greater than that of low education, a conventional measure of socioeconomic disadvantage. By contrast, outdegree, which reflects an individual's perceived connectedness, displays a significantly weaker association with fibrinogen concentrations.

Changes in Allostatic Load during workplace reorganization

OBJECTIVE

Allostatic Load (AL) represents the strain on the body produced by repeated physiologic or allostatic responses activated during stressful situations. Several cross-sectional studies have found empirical substantiation for the relationship between impaired psychosocial work environment and high AL. The aim of this longitudinal study is to investigate changes in AL during workplace reorganization that has been shown to cause impaired psychosocial work environment. Moreover, we aim to investigate the association between changes in AL and changes in psychosocial work environment (job strain, effort-reward imbalance) and psychological distress (stress symptoms and perceived stress).

METHODS

A major reorganization of non-state public offices was effectuated in Denmark on 1 January 2007. In 2006 and 2008, we collected clinical and questionnaire data from 359 participants, 265 women and 94 men, employed in seven municipality or county administrations. Four municipalities and one county merged with others, while one municipality and one county remained unmerged. We calculated the AL score based on 13 physiological markers reflecting stress responses of the cardiovascular, metabolic, neuroendocrine and immune systems. We analysed changes in AL from 2006 to 2008.

RESULTS

AL increased significantly during workplace reorganization in the whole study group but we observed only a tendency of significant increase in AL in the merger group compared with the control group. Moreover, we observed no association between the changes in AL and changes in psychosocial work environment and psychological distress.

CONCLUSIONS

This result leaves the conclusion unclear but contributes to the limited research in this area with a longitudinal design and focus on low-risk levels and small changes in AL in healthy people as predictor of future disease.

Molecular and functional genetics of the proopiomelanocortin gene, food intake regulation and obesity

A specter is haunting the world, the specter of obesity. During the last decade, this pandemia has skyrocketed threatening children, adolescents and lower income families worldwide. Although driven by an increase in the consumption of ultraprocessed edibles of poor nutritional value, the obesogenic changes in contemporary human lifestyle affect people differently, revealing that some individuals are more prone to develop increased adiposity. During the last years, we performed a variety of genetic, evolutionary, biochemical and behavioral experiments that allowed us to understand how a group of neurons present in the arcuate nucleus of the hypothalamus regulate the expression of the proopiomelanocortin (Pomc) gene and induce satiety. We disentangled the neuronal transcriptional code of Pomc by identifying the cis-acting regulatory elements and primary transcription factors controlling hypothalamic Pomc expression and determined their functional importance in the regulation of food intake and adiposity. Altogether, our studies reviewed here shed light on the power and limitations of the mammalian central satiety pathways and may contribute to the development of individual and collective strategies to reduce the debilitating effects of the self-induced obesity pandemia.

Allostatic load and comorbidities: A mitochondrial, epigenetic, and evolutionary perspective

Stress-related pathophysiology drives comorbid trajectories that elude precise prediction. Allostatic load algorithms that quantify biological "wear and tear" represent a comprehensive approach to detect multisystemic disease processes of the mind and body. However, the multiple morbidities directly or indirectly related to stress physiology remain enigmatic. Our aim in this article is to propose that biological comorbidities represent discrete pathophysiological processes captured by measuring allostatic load. This has applications in research and clinical settings to predict physical and psychiatric comorbidities alike. The reader will be introduced to the concepts of allostasis, allostasic states, allostatic load, and allostatic overload as they relate to stress-related diseases and the proposed prediction of biological comorbidities that extend rather to understanding psychopathologies. In our transdisciplinary discussion, we will integrate perspectives related to (a) mitochondrial biology as a key player in the allostatic load time course toward diseases that "get under the skin and skull"; (b) epigenetics related to child maltreatment and biological embedding that shapes stress perception throughout lifespan development; and

Impaired glucose metabolism moderates the course of illness in bipolar disorder

BACKGROUND

The longitudinal course of bipolar disorder (BD) is highly heterogeneous, and is moderated by the presence of general medical comorbidities. This study aimed to investigate the moderating effects of impaired glucose metabolism (IGM) on variables of illness course and severity in a BD population.

METHODS

Fifty-five patients with BD were evaluated. All subjects were evaluated with respect to current and past psychiatric and medical disorders, as well as lifetime use of any medication. Body mass index (BMI) and metabolic parameters were obtained. IGM was operationalized as pre-diabetes or type 2 diabetes mellitus.

RESULTS

Thirty (54.5%) individuals had IGM. After adjustment for age, gender, ethnicity, alcohol use, smoking, BMI and past and current exposure to psychotropic medications, individuals with IGM, when compared to euglycemic participants, had an earlier age of onset (RR: 0.835, p=0.024), longer illness duration (RR: 1.754, p=0.007), a higher number of previous manic/hypomanic episodes (RR: 1.483, p=0.002) and a higher ratio of manic/hypomanic to depressive episodes (RR: 1.753, p=0.028). Moreover, we observed a moderating effect of IGM on the association between number of mood episodes and other variables of illness course, with the correlation between lifetime mood episodes and frequency of episodes being significantly greater in the IGM subgroup (RR: 1.027, p=0.029). All associations observed herein remained significant after adjusting for relevant confounding factors (e.g. age, alcohol and tobacco use, exposure to psychotropic agents, BMI).

LIMITATIONS

Cross-sectional design, small sample size.

CONCLUSIONS

Comorbid IGM may be a key moderator of illness progression in BD.

Adipokines, metabolic dysfunction and illness course in bipolar disorder

Replicated evidence indicates that individuals with BD are differentially affected by metabolic comorbidities and that its occurrence is a critical mediator and/or moderator of BD outcomes. This study aimed to explore the role of adipokines on bipolar disorder (BD) course and its relationship with metabolic comorbidities (i.e. type 2 diabetes mellitus, obesity). We measured plasma levels of adiponectin and leptin, as well as anthropometric and metabolic parameters of 59 patients with BD and 28 healthy volunteers. Our results showed that, in female participants, adiponectin was lower in individuals with BD, relative to healthy controls (p = 0.017). In the BD population, adiponectin levels were correlated with fasting glucose (r = -0.291, p = 0.047), fasting insulin (r = -0.332, p = 0.023), C-peptide (r = 0.040, p = 0.040), homeostatic model assessment-insulin resistance (r = -0.411, p = 0.004), HDL (r = 0.508, p < 0.001), VLDL (r = -0.395, p = 0.005) and triglycerides (r = -0.310, p = 0.030). After adjustment for age, gender and BMI, individuals with BD and low adiponectin levels (i.e. < 7.5 μg/ml), had a higher number of mood episodes (p < 0.001), lower number of psychiatric hospitalizations (p = 0.007), higher depressive symptoms (p < 0.001) and lower levels of functioning (p = 0.020). In conclusion, adiponectin levels, either directly or as a proxy of metabolic dysfunction, is independently associated with an unfavorable course of illness in BD.

Adolescents' internalizing and externalizing problems predict their affect-specific HPA and HPG axes reactivity

We examined psychopathology-neuroendocrine associations in relation to the transition into adolescence within a developmental framework that acknowledged the interdependence of the HPA and HPG hormone systems in the regulation of responses to everyday affective contexts. Saliva samples were collected during anxiety and anger inductions from 51 young adolescents (M 13.47, SD = .60 years) to evaluate cortisol, DHEA, and testosterone responses. Internalizing and externalizing problems were assessed at pre-adolescence (M = 9.27, SD = .58 years) while youths were in elementary school and concurrently with hormones in early adolescence. Externalizing problems from elementary school predicted adolescents' reduced DHEA reactivity during anxiety induction. Follow up analyses simultaneously examining the contributions of elementary school and adolescent problems showed a trend suggesting that youths with higher levels of internalizing problems during elementary school eventuated in a profile of heightened DHEA reactivity as adolescents undergoing anxiety induction. For both the anxiety and the anger inductions, it was normative for DHEA and testosterone to be positively coupled. Adolescents with high externalizing problems but low internalizing problems marshaled dual axes co-activation during anger induction in the form of positive cortisol-testosterone coupling. This is some of the first evidence suggesting affective context determines whether dual axes coupling is reflective of normative or problematic functioning in adolescence.

Is there a "metabolic-mood syndrome"? A review of the relationship between obesity and mood disorders

Obesity and mood disorders are highly prevalent and co-morbid. Epidemiological studies have highlighted the public health relevance of this association, insofar as both conditions and its co-occurrence are associated with a staggering illness-associated burden. Accumulating evidence indicates that obesity and mood disorders are intrinsically linked and share a series of clinical, neurobiological, genetic and environmental factors. The relationship of these conditions has been described as convergent and bidirectional; and some authors have attempted to describe a specific subtype of mood disorders characterized by a higher incidence of obesity and metabolic problems. However, the nature of this association remains poorly understood. There are significant inconsistencies in the studies evaluating metabolic and mood disorders; and, as a result, several questions persist about the validity and the generalizability of the findings. An important limitation in this area of research is the noteworthy phenotypic and pathophysiological heterogeneity of metabolic and mood disorders. Although clinically useful, categorical classifications in both conditions have limited heuristic value and its use hinders a more comprehensive understanding of the association between metabolic and mood disorders. A recent trend in psychiatry is to move toward a domain specific approach, wherein psychopathology constructs are agnostic to DSM-defined diagnostic categories and, instead, there is an effort to categorize domains based on pathogenic substrates, as proposed by the National Institute of Mental Health (NIMH) Research Domain Criteria Project (RDoC). Moreover, the substrates subserving psychopathology seems to be unspecific and extend into other medical illnesses that share in common brain consequences, which includes metabolic disorders. Overall, accumulating evidence indicates that there is a consistent association of multiple abnormalities in neuropsychological constructs, as well as correspondent brain abnormalities, with broad-based metabolic dysfunction, suggesting, therefore, that the existence of a "metabolic-mood syndrome" is possible. Nonetheless, empirical evidence is necessary to support and develop this concept. Future research should focus on dimensional constructs and employ integrative, multidisciplinary and multimodal approaches.

Parameters of hormetic stress and resilience to trauma in rats

Hormesis is the process by which small stresses build resilience to large stresses. We pre-exposed rats to various parameters of mild-to-moderate stress prior to traumatic stress in the present experiments to assess the potential benefits of hormetic training on resilience to traumatic, uncontrollable stress. Rats underwent varying stress pre-training parameters prior to exposure to uncontrollable traumatic stress in the learned helplessness procedure. The ability to prevent the exaggerated fear responding and escape deficits that normally follow experience with traumatic stress were used as a measure of the benefits of hormetic training. Four experiments examined the effects of number of training sessions, stressor severity and pattern of rest between pre-training stress sessions. Repeated exposure to mild restraint stress or moderate shock stress eliminated both the enhanced fear conditioning and shuttle-escape deficits that result from exposure to traumatic, inescapable shock. The pattern of rest did not contribute to resilience when the pre-exposure stressor was mild, but was vital when the pre-exposure stressor was moderate, with an alternation of stress and rest being the most effective procedure. The data also suggest that the level of resilience may increase with the number of pre-exposure sessions.

The trauma of peer abuse: effects of relational peer victimization and social anxiety disorder on physiological and affective reactions to social exclusion

BACKGROUND

Social exclusion elicits emotional distress, negative mood, and physiological stress. Recent studies showed that these effects were more intense and persisting in socially anxious subjects. The present study examined whether the abnormal reactions of socially anxious subjects can be traced back to previous experiences of relational peer victimization during childhood and adolescence.

METHODS

Participants (N = 74) were patients with a diagnosis of social anxiety disorder as well as healthy controls. The patient and control groups were subdivided into two subgroups according to the subject's reports about previous relational peer victimization. Immediate and delayed physiological (skin conductance level and heart rate) and affective reactions to a simulated social exclusion in a ball-toss game (Cyberball) were recorded.

RESULTS

Overall, subjects' immediate reactions to social exclusion were an increase in skin conductance and a reduction of positive affect. Regardless of the diagnostic status, subjects with a history of relational peer victimization showed a more intense self-reported affective change that was accompanied by a blunted skin conductance response. However, the mood of the subjects with a history of peer victimization recovered during a 15 min waiting period. A diagnosis of social anxiety disorder did not affect the reactions to social exclusion on any measure.

CONCLUSION

Findings indicate that stress reactions to social exclusion depend more on previous experiences of peer victimization than on a diagnosis of social anxiety disorder. The findings indicate that memories of negative social experiences can determine the initial stress reaction to social threats.

Predicting all-cause and cause-specific mortality by static and dynamic measurements of allostatic load: a 10-year population-based cohort study in Taiwan

OBJECTIVE

To evaluate the role of allostatic load (AL), either static or dynamic measurements, in predicting all-cause and cause-specific mortality of older people in Taiwan.

DESIGN

A prospective cohort study.

SETTING

Population-based community study.

PARTICIPANTS

One thousand twenty-three community-dwelling older people.

MEASUREMENTS

Allostatic load (calculated by systolic blood pressure, diastolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, triglyceride, glycosylated hemoglobin, fasting glucose, waist-to-hip ratio, body mass index, dehydroepiandrosterone sulfate, insulin-like growth factor-1, 12-hour urine cortisol, 12-hour urine epinephrine, 12-hour urine norepinephrine, 12-hour urine dopamine, white blood cell count, neutrophils, interleukin-6, albumin, creatinine) and all-cause and cause-specific mortality from national death registry.

INTERVENTION

None.

RESULTS

Adjusted for age and sex, each 1-point increase in AL score was associated with 20% incremental risk of mortality [hazard ratio 1.20, 95% confidence interval (CI) 1.09-1.31]. This association can be extended to cause-specific mortality in both sexes in general. In addition, the higher AL score quintile was significantly associated with higher risk of 10-year all-cause mortality (P < .0001). This association was consistent across different cause-specific mortality (ie, malignant neoplasm (P = .008), cardiometabolic diseases (P < .0001), infectious diseases (P < .0001), respiratory diseases (P < .0001), and others (P = .0002), respectively. Compared with AL score decliners, adjusted for age, sex, and baseline AL score in 2000, participants with fast increase had significantly higher mortality (HR 2.68, 95% CI 1.23-5.84, P = .01). The effect was stronger in men (HR 2.83, 95% CI 1.1-7.29, P = .03 in slow increase; HR 4.06, 95% CI 1.56-10.6, P = .001 in fast increase group), but it was insignificant in female participants.

CONCLUSIONS

Higher AL score or rapid increase of AL score significantly increased subsequent mortality risk in older adults, either measured statically or dynamically. AL is predictive of 10-year mortality regardless of cause of death, and rapid increase in AL score is associated with higher subsequent mortality.

Allostasis as a conceptual framework linking bipolar disorder and addiction

Bipolar disorders (BDs) and addictions constitute reciprocal risk factors and are best considered under a unitary perspective. The concepts of allostasis and allostatic load (AL) may contribute to the understanding of the complex relationships between BD and addictive behaviors. Allostasis entails the safeguarding of reward function stability by recruitment of changes in the reward and stress system neurocircuitry and it may help to elucidate neurobiological underpinnings of vulnerability to addiction in BD patients. Conceptualizing BD as an illness involving the cumulative build-up of allostatic states, we hypothesize a progressive dysregulation of reward circuits clinically expressed as negative affective states (i.e., anhedonia). Such negative affective states may render BD patients more vulnerable to drug addiction, fostering a very rapid transition from occasional drug use to addiction, through mechanisms of negative reinforcement. The resulting addictive behavior-related ALs, in turn, may contribute to illness progression. This framework could have a heuristic value to enhance research on pathophysiology and treatment of BD and addiction comorbidity.

Application of the model of allostasis to older women's relocation to senior housing

OBJECTIVES

Adjustment to senior housing entails significant lifestyle changes and is a stressful process. The adaptation process is dynamic and has yet to be studied using the conceptual model of allostasis. This article presents exemplars of women whose profiles represent three allostatic states: successful adaptation (homeostasis), ongoing adaptation (allostasis), and maladaptation (allostatic load).

METHOD

Older women who had relocated to senior housing participated in three interviews and monthly saliva sample collection over a 6-month period. Saliva was assayed for diurnal cortisol secretion. Triangulation of mixed methods was used to analyze data, and psychosocial data were mapped onto the cortisol graphs to illustrate changes in stress reactivity and well-being.

RESULTS

Coping abilities, perceptions of stressors, and cortisol measures provide a detailed picture of the interplay among events and perceptions and the effects of both on well-being.

DISCUSSION

The case exemplars provide detailed information on the complexity of psychosocial and physiological components of the model of allostasis. This study also fills a gap in knowledge on negative relocation outcomes using the allostatic model.

Obesity-programmed mice are rescued by early genetic intervention

Obesity is a chronic metabolic disorder affecting half a billion people worldwide. Major difficulties in managing obesity are the cessation of continued weight loss in patients after an initial period of responsiveness and rebound to pretreatment weight. It is conceivable that chronic weight gain unrelated to physiological needs induces an allostatic regulatory state that defends a supranormal adipose mass despite its maladaptive consequences. To challenge this hypothesis, we generated a reversible genetic mouse model of early-onset hyperphagia and severe obesity by selectively blocking the expression of the proopiomelanocortin gene (Pomc) in hypothalamic neurons. Eutopic reactivation of central POMC transmission at different stages of overweight progression normalized or greatly reduced food intake in these obesity-programmed mice. Hypothalamic Pomc rescue also attenuated comorbidities such as hyperglycemia, hyperinsulinemia, and hepatic steatosis and normalized locomotor activity. However, effectiveness of treatment to normalize body weight and adiposity declined progressively as the level of obesity at the time of Pomc induction increased. Thus, our study using a novel reversible monogenic obesity model reveals the critical importance of early intervention for the prevention of subsequent allostatic overload that auto-perpetuates obesity.

A theoretical framework informing research about the role of stress in the pathophysiology of bipolar disorder

BACKGROUND

The staggering illness burden associated with Bipolar Disorder (BD) invites the need for primary prevention strategies. Before preventative strategies can be considered in individuals during a pre-symptomatic period (i.e., at risk), unraveling the mechanistic steps wherein external stress is transduced and interacts with genetic vulnerability in the early stages of BD will be a critical conceptual necessity.

METHODS

Herein we comprehensively review extant studies reporting on stress and bipolar disorder. The overarching aim is to propose a conceptual framework to inform research about the role of stress in the pathophysiology of BD. Computerized databases i.e. PubMed, PsychInfo, Cochrane Library and Scielo were searched using the following terms: "bipolar disorder" cross-referenced with "stress", "general reaction to stress", "resilience", "resistance", "recovery" "stress-diathesis", "allostasis", and "hormesis".

RESULTS

Data from literature indicate the existence of some theoretical models to understand the influence of stress in the pathophysiology of BD, including classical stress-diathesis model and new models such as allostasis and hormesis. In addition, molecular mechanisms involved in stress adaptation (resistance, resilience and recovery) can also be translated in research strategies to investigate the impact of stress in the pathophysiology of BD.

LIMITATIONS

Most studies are retrospective and/or cross sectional, do not consider the period of development, assess brain function with only one or few methodologies, and use animal models which are not always similar to human phenotypes.

CONCLUSION

The interaction between stress and brain development is dynamic and complex. In this article we proposed a theoretical model for investigation about the role of stress in the pathophysiology of BD, based on the different kinds of stress adaptation response and their putative neurobiological underpinnings.

The clinical implications of cognitive impairment and allostatic load in bipolar disorder

BACKGROUND

Allostatic load (AL) relates to the neural and bodily "wear and tear" that emerge in the context of chronic stress. This paper aims to provide clinicians with a comprehensive overview of the role of AL in patophysiology of bipolar disorder (BD) and its practical implications.

METHODS

PubMed searches were conducted on English-language articles published from 1970 to June 2011 using the search terms allostatic load, oxidative stress, staging, and bipolar disorder cross-referenced with cognitive impairment, comorbidity, mediators, prevention.

RESULTS

Progressive neural and physical dysfunction consequent to mood episodes in BD can be construed as a cumulative state of AL. The concept of AL can help to reconcile cognitive impairment and increased rates of clinical comorbidities that occur over the course of cumulative BD episodes.

CONCLUSIONS

Data on transduction of psychosocial stress into the neurobiology of mood episodes converges to the concept of AL. Mood episodes prevention would not only alleviate emotional suffering, but also arrest the cycle of AL, cognitive decline, physical morbidities and, eventually, related mortality. These objectives can be achieved by focusing on effective prophylaxis from the first stages of the disorder, providing mood-stabilizing agents and standardized psychoeducation and, potentially, addressing cognitive deficits by the means of specific medication and neuropsychological interventions.

A developmental increase in allostatic load from ages 3 to 11 years is associated with increased schizotypal personality at age 23 years

Although allostatic load has been investigated in mood and anxiety disorders, no prior study has investigated developmental change in allostatic load as a precursor to schizotypal personality. This study employed a multilevel developmental framework to examine whether the development of increased allostatic load, as indicated by impaired sympathetic nervous system habituation from ages 3 to 11 years, predisposes to schizotypal personality at age 23 years. Electrodermal activity to six aversive tones was recorded in 995 subjects at age 3 years and again at 11 years. Habituation slopes at both ages were used to create groups who showed a developmental increase in habituation (decreased allostatic load), and those who showed a developmental decrease in habituation (increased allostatic load). Children who showed a developmental increase in allostatic load from ages 3 to 11 years had higher levels of schizotypal personality at 23 years. A breakdown of total schizotypy scores demonstrated specificity of findings to cognitive-perceptual features of schizotypy. Findings are the first to document a developmental abnormality in allostasis in relation to adult schizotypal personality. The relative failure to develop normal habituation to repeated stressors throughout childhood is hypothesized to result in an accumulation of allostatic load and consequently increased positive symptom schizotypy in adulthood.

Diurnal cortisol rhythms in Tsimane' Amazonian foragers: new insights into ecological HPA axis research

Although a growing body of research has documented important pathways by which the HPA axis mediates the interface between the psychosocial world and individual health, there is a paucity of data from nonwestern populations, particularly from those populations with distinct nutritional and infectious disease ecologies. The specific objectives of this study are: (1) to document variation in diurnal cortisol rhythms among the Tsimane', a remote population in the Bolivian Amazon, (2) to explore this variation by age and by gender, and (3) to compare diurnal rhythms from this study to other population based studies of cortisol conducted in industrialized nations. Salivary cortisol samples were collected twice daily, immediately upon waking and before bed, for three consecutive days from 303 participants (age 1.6-82 years, 1564 samples) in conjunction with the Tsimane' Amazonian Panel Study (TAPS). Cortisol rhythms showed strong age effects across the developmental span, with basal levels and slopes increasing into adulthood, although individuals older than 60 years demonstrated a precipitous flattening of the diurnal slope. Cortisol profiles were elevated in adult females compared to their age-matched male counterparts, and diurnal slopes, as well as mean cortisol concentrations among the Tsimane' were the lowest reported in any population based study of HPA axis function. Although the within-population variation in cortisol profiles was consistent with the established correlates of time of day, age, and sex, the between-population comparisons revealed dramatically lower levels of HPA activity among the Tsimane'. This study provides a benchmark against which to reference cortisol levels from industrialized populations, and expands the range of documented variation in HPA axis function in a nonwestern context.

Blunted cortisol responses to stress signal social and behavioral problems among maltreated/bullied 12-year-old children

BACKGROUND

Evidence from animal and human studies suggests that early-life stress such as physical maltreatment has long-lasting effects on the hypothalamic-pituitary-adrenal (HPA) axis and is associated with blunted HPA axis reactivity in adulthood. Few studies have investigated whether blunted HPA axis reactivity observed in children exposed to early-life stress signals social, emotional, and behavioral problems.

METHODS

Participants were 190 12-year-old children (50.5% males) recruited from the Environmental Risk Longitudinal Twin Study, a nationally representative 1994 to 1995 cohort of families with twins. Cortisol responses to psychosocial stress were measured in maltreated/bullied (n = 64) and comparison children (n = 126). We ascertained maltreatment and bullying victimization using mothers' reports and assessed children's social, emotional, and behavioral problems at ages 5 and 12 using mothers' and teachers' reports.

RESULTS

Piecewise multilevel growth curve analyses indicated that maltreated/bullied and comparison children showed distinct cortisol responses to stress. Specifically, maltreated/bullied children had lower cortisol responses than comparison children who exhibited a significant increase. Lower cortisol responses were, in turn, associated with more social and behavioral problems among maltreated/bullied children.

CONCLUSIONS

These findings provide support for the influence of childhood harm on blunted HPA axis reactivity and its potential impact on children's functioning. Our findings emphasize the need to integrate stress biomarkers in guiding prevention efforts for young victims.

Interactive effects of corticotropin releasing hormone receptor 1, serotonin transporter linked polymorphic region, and child maltreatment on diurnal cortisol regulation and internalizing symptomatology

Within an allostatic load framework, the effect of Gene × Environment (G × E) interactions on diurnal cortisol regulation and internalizing symptomatology were investigated. Variation in the corticotropin releasing hormone receptor 1 (CRHR1) TAT haplotype and serotonin transporter linked polymorphic region (5-HTTLPR) was determined in a sample of maltreated (n = 238, 21.4% with early physical and sexual abuse) and nonmaltreated (n = 255) children (M age = 10.08) participating in a summer research camp. Internalizing and depressive symptoms were assessed by other and self-report. G × E effects for CRHR1 and maltreatment and early abuse on diurnal cortisol regulation were observed; CRHR1 variation was related to cortisol dysregulation only among maltreated children. Early abuse and high internalizing symptoms also interacted to predict atypical diurnal cortisol regulation. The interaction of CRHR1, 5-HTTLPR, and child maltreatment (G × G × E) identified a subgroup of maltreated children with high internalizing symptoms who shared the same combination of the two genes. The findings support an allostatic load perspective on the effects of the chronic stress associated with child maltreatment on cortisol regulation and internalizing symptomatology as moderated by genetic variation.

Increased testosterone-to-cortisol ratio in psychopathy

Only a few studies have examined hormones in psychopathy, and results have been mixed. It has been suggested that because hormone systems are highly interconnected, it may be important to examine multiple systems simultaneously to gain a clearer picture of how hormones work together to predispose for a certain construct. In the present study, we attempt to clarify the role of the hormones cortisol and testosterone in psychopathy by examining both hormones in a community sample of 178 adults demonstrating a wide range of psychopathy scores. Results showed that psychopathy scores were associated with an increased ratio of testosterone (baseline) to cortisol responsivity to a stressor. Psychopathy was not associated with either of these measures independently or with baseline cortisol levels. These findings suggest that these highly interconnected hormone systems may work in concert to predispose to psychopathy.

A transdisciplinary perspective of chronic stress in relation to psychopathology throughout life span development

The allostatic load (AL) model represents an interdisciplinary approach to comprehensively conceptualize and quantify chronic stress in relation to pathologies throughout the life cycle. This article first reviews the AL model, followed by interactions among early adversity, genetics, environmental toxins, as well as distinctions among sex, gender, and sex hormones as integral antecedents of AL. We next explore perspectives on severe mental illness, dementia, and caregiving as unique human models of AL that merit future investigations in the field of developmental psychopathology. A complimenting transdisciplinary perspective is applied throughout, whereby we argue that the AL model goes beyond traditional stress–disease theories toward the advancement of person-centered research and practice that promote not only physical health but also mental health.

The neurobiology of psychopathy: a neurodevelopmental perspective

We provide an overview of the neurobiological underpinnings of psychopathy. Cognitive and affective-emotional processing deficits are associated with abnormal brain structure and function, particularly the amygdala and orbitofrontal cortex. There is limited evidence of lower cortisol levels being associated with psychopathic personality. Initial developmental research is beginning to suggest that these neurobiological processes may have their origins early in life. Findings suggest that psychopathic personality may, in part, have a neurodevelopmental basis. Future longitudinal studies delineating neurobiological correlates of the analogues of interpersonal-affective and antisocial features of psychopathy in children are needed to further substantiate a neurodevelopmental hypothesis of psychopathy.

The testosterone-cortisol ratio: A hormonal marker for proneness to social aggression

Social aggression is an escalating hazard for individuals and society. It is most frequently observed as impulsive-reactive aggression in antisocial personality disorder (APD), but in psychopathic aggressive personalities instrumental social aggression is more prominent. However, the psychobiological mechanisms underlying human social aggression are still poorly understood. Here we propose a psychobiological mechanism that may explain human social aggression wherein the steroid hormones cortisol and testosterone play a critical role. High levels of testosterone and low levels of cortisol have been associated with social aggression in several species but it seems that in those individuals wherein these hormonal markers combine social aggression is most violent. In this review we discuss fundamental and clinical research which underscores the potential of the testosterone-cortisol ratio as a possible marker for criminal aggressive tendencies.

The neurobiology of psychopathy

Numerous studies have tackled the complex challenge of understanding the neural substrates of psychopathy, revealing that brain abnormalities exist on several levels and in several structures. As we discover more about complex neural networks, it becomes increasingly difficult to clarify how these systems interact with each other to produce the distinct pattern of behavioral and personality characteristics observed in psychopathy. The authors review the recent research on the neurobiology of psychopathy, beginning with molecular neuroscience work and progressing to the level of brain structures and their connectivity. Potential factors that may affect the development of brain impairments, as well as how some systems may be targeted for potential treatment, are discussed.

CRH haplotype as a factor influencing cerebrospinal fluid levels of corticotropin-releasing hormone, hypothalamic-pituitary-adrenal axis activity, temperament, and alcohol consumption in rhesus macaques

CONTEXT

Both highly stress-reactive and novelty-seeking individuals are susceptible to alcohol use disorders. Variation in stress reactivity, exploration, and response to novelty have been attributed to differences in corticotropin-releasing hormone (CRH) system function. As such, CRH gene variation may influence risk for alcohol use and dependence.

OBJECTIVE

To determine whether CRH variation influences relevant intermediate phenotypes, behavior, and alcohol consumption in rhesus macaques.

DESIGN

We sequenced the rhesus macaque CRH locus (rhCRH) and performed cladistic clustering of haplotypes. In silico analysis, gel shift, and in vitro reporter assays were performed to identify functional variants. Cerebrospinal fluid (CSF) and blood samples were obtained, and levels of CRH and corticotropin (ACTH) were measured by radioimmunoassay. Behavioral data were collected from macaques during infancy. Among adolescent/adult animals, we recorded responses to an unfamiliar conspecific and measured levels of ethanol consumption.

SETTING

National Institutes of Health Animal Center.

PARTICIPANTS

Rhesus macaques.

MAIN OUTCOME MEASURES

Animals were genotyped for a single-nucleotide polymorphism disrupting a glucocorticoid response element, rhCRH -2232 C>G, and the effects of this allele on CSF levels of CRH, plasma levels of ACTH, behavior, and ethanol consumption were assessed by analysis of variance.

RESULTS

We show that -2232C>G alters DNA x protein interactions and confers decreased sensitivity of the CRH promoter to glucocorticoids in vitro. Consistent with the known effects of glucocorticoids on CRH expression in the brain, carriers of the G allele had lower CSF levels of CRH but higher levels of ACTH. Infants carrying the G allele were more exploratory and bold, and among adolescent and adult male macaques, the G allele was associated with exploratory/bold responding to an unfamiliar male. Adults with the C/G genotype also exhibited increased alcohol consumption in the social group, a model for high-risk alcohol-seeking behavior.

CONCLUSION

Haplotypes that differ in terms of corticosteroid sensitivity have been identified in humans. Our data may suggest that functionally similar CRH variants could influence risk for externalizing disorders in human subjects.

Homeostasis: beyond Curt Richter

Curt Richter introduced behavioral control into the concept of homeostasis, thereby opening entire fields of research. The prevailing dogma, and the techniques he used, conspired to lead Richter and others to interpret regulation in strict negative feedback terms. Although this point of view continues to be embraced by many contemporary biologists, we believe that prevailing sentiment favors a broader view in which organisms integrate anticipatory pre-emptive control over regulated variables whenever possible.