Psychological and stress hormone correlates in early life: a key to HPA-axis dysregulation and normalisation

Associations of prenatal maternal depressive symptoms with cord blood glucocorticoids and child hair cortisol levels in the project viva and the generation R cohorts: a prospective cohort study

BACKGROUND

Prior studies have reported conflicting results regarding the association of prenatal maternal depression with offspring cortisol levels. We examined associations of high levels of prenatal depressive symptoms with child cortisol biomarkers.

METHODS

In Project Viva (n = 925, Massachusetts USA), mothers reported their depressive symptoms using the Edinburgh Postnatal Depression Scale (EPDS) during pregnancy, cord blood glucocorticoids were measured at delivery, and child hair cortisol levels were measured in mid-childhood (mean (SD) age: 7.8 (0.8) years) and early adolescence (mean (SD) age: 13.2 (0.9) years). In the Generation R Study (n = 1644, Rotterdam, The Netherlands), mothers reported depressive symptoms using the Brief Symptom Inventory (BSI) during pregnancy, and child hair cortisol was measured at a mean (SD) age of 6.0 (0.5) years. We used cutoffs of ≥ 13 for the EPDS and > 0.75 for the BSI to indicate high levels of prenatal depressive symptoms. We used multivariable linear regression models adjusted for child sex and age (at outcome), and maternal pre-pregnancy BMI, education, social support from friends/family, pregnancy smoking status, marital status, and household income to assess associations separately in each cohort. We also meta-analyzed childhood hair cortisol results from both cohorts.

RESULTS

8.0% and 5.1% of women respectively experienced high levels of prenatal depressive symptoms in Project Viva and the Generation R Study. We found no associations between high levels of maternal depressive symptoms during pregnancy and child cortisol biomarkers in either cohort.

CONCLUSIONS

The present study does not find support for the direct link between high levels of maternal depressive symptoms and offspring cortisol levels.

Adipocytokine correlates of childhood and adolescent mental health: A systematic review

The objective of this systematic review was to determine the current state of the literature regarding how adipocytokines associate with mental health symptoms/disorders in youth. Findings summarized in this review suggested that in neurodevelopmental disorders, higher levels of leptin, ghrelin, resistin, and visfatin as well as lower levels of adiponectin, retinol-binding protein 4, and progranulin predicted increased risk for or were conflated with autism spectrum disorder. Adipocytokine correlates of attention-deficit hyperactivity disorder and related symptoms included higher apelin, higher leptin-to-adiponectin ratio, and lower adiponectin. Evidence from studies examining anxiety symptoms evinced mixed results regarding leptin, and one study suggested higher levels of ghrelin. Depressive symptoms correlated with higher leptin and ghrelin. Research examining posttraumatic stress symptoms found higher levels of ghrelin. In research examining broadband symptoms, conflicting results emerged for associations between internalizing symptoms (i.e., symptoms of emotional stress) and leptin in youth. Low levels of adiponectin and high levels of leptin predicted externalizing symptoms. Total symptom difficulties were associated with a higher leptin-to-adiponectin ratio. Our findings suggest that adipocytokines may be an important set of biomarkers to consider as underlying mechanisms contributing to developmental psychopathology.

Stress-induced symptom exacerbation: Stress increases voiding frequency, somatic sensitivity, and urinary bladder NGF and BDNF expression in mice with subthreshold cyclophosphamide (CYP)

Symptom exacerbation due to stress is prevalent in many disease states, including functional disorders of the urinary bladder (e.g., overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS)); however, the mechanisms underlying the effects of stress on micturition reflex function are unclear. In this study we designed and evaluated a stress-induced symptom exacerbation (SISE) mouse model that demonstrates increased urinary frequency and somatic (pelvic and hindpaw) sensitivity. Cyclophosphamide (CYP) (35 mg/kg; i.p., every 48 hours for a total of 4 doses) or 7 days of repeated variate stress (RVS) did not alter urinary bladder function or somatic sensitivity; however, both CYP alone and RVS alone significantly (p ≤ 0.01) decreased weight gain and increased serum corticosterone. CYP treatment when combined with RVS for 7 days (CYP+RVS) significantly (p ≤ 0.01) increased serum corticosterone, urinary frequency and somatic sensitivity and decreased weight gain. CYP+RVS exposure in mice significantly (p ≤ 0.01) increased (2.6-fold) voiding frequency as we determined using conscious, open-outlet cystometry. CYP+RVS significantly (p ≤ 0.05) increased baseline, threshold, and peak micturition pressures. We also evaluated the expression of NGF, BDNF, CXC chemokines and IL-6 in urinary bladder in CYP alone, RVS alone and CYP+RVS mouse cohorts. Although all treatments or exposures increased urinary bladder NGF, BDNF, CXC and IL-6 content, CYP+RVS produced the largest increase in all inflammatory mediators examined. These results demonstrated that CYP alone or RVS alone creates a change in the inflammatory environment of the urinary bladder but does not result in a change in bladder function or somatic sensitivity until CYP is combined with RVS (CYP+RVS). The SISE model of CYP+RVS will be useful to develop testable hypotheses addressing underlying mechanisms where psychological stress exacerbates symptoms in functional bladder disorders leading to identification of targets and potential treatments.

Influence of occupational exposure on hyperuricemia in steelworkers: a nested case-control study

BACKGROUND

Occupational exposure may be associated with an increased risk of developing hyperuricemia. This study sheds lights on the association between occupational exposure and hyperuricemia in steelworkers.

METHOD

A nested case-control study was conducted within a cohort of workers in steel companies to explore the association between occupational exposure and hyperuricemia. The case group consisted of a total of 641 cases of hyperuricemia identified during the study period, while 641 non-hyperuricemia subjects with the same age and gender distribution were randomly selected from the cohort as the control group.

RESULTS

The incidence rate of hyperuricemia among workers in the steel company was 17.30%, with an incidence density of 81.32/1,000 person-years. In comparison to the reference group, the risks of developing hyperuricemia for steelworkers undergoing ever shifts, current shifts, heat exposure, and dust exposure were 2.18 times, 1.81 times, 1.58 times and 1.34 times higher respectively. The odds ratios (ORs) and 95% confidence intervals (CIs) were 1.87(1.12-3.13) and 2.02(1.21-3.37) for the cumulative number of days of night work at 0-1,972.80 and ≥ 1,972.80 (days), respectively. Compared to the group with the cumulative heat exposure of 0 (°C/year), the ORs (95% CI) for the risk of developing hyperuricemia in the groups with the cumulative heat exposure of 0-567.83 and ≥ 567.83 (°C/year) were 1.50(1.02-2.22) and 1.64(1.11-2.43), respectively. The OR (95% CI) for the risk of developing hyperuricemia was 1.56(1.05-2.32) at the cumulative dust exposure of ≥ 30.02 (mg/m³/year) compared to that at the cumulative dust exposure of 0 (mg/m³/year). Furthermore, there was a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia.

CONCLUSION

Shift work, heat, and dust are independent risk factors for the development of hyperuricemia in steelworkers. Additionally, there is a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia. Interventions for shift work, heat and dust may help to reduce the incidence rate of hyperuricemia and improve the health of steelworkers.

Metabolic proteins at birth predict early childhood mental health symptoms

Child mental health disorders are the leading cause of disability in children and adolescents worldwide. Biological correlates predict psychosocial outcomes throughout human development; however, less is known about metabolic proteins. Drawing from a longitudinal birth cohort study, Born in Bradford (BiB), we examined the role of infant metabolic proteins at birth in predicting early childhood mental health symptoms at 3 and 5 years. We found that higher leptin predicted more prosocial behavior at age 3. Additionally, a higher leptin-to-adiponectin ratio predicted increased total symptom difficulties. At age 5, we found that higher adiponectin predicted a decreased likelihood of being rated by teachers as meeting or exceeding expectations in the domain of "managing feelings and behaviors" and marginally predicted lower competency in "making relationships" on national developmental milestone evaluations. To our knowledge, this is among the first few studies to prospectively predict mental health symptoms from cord blood metabolic proteins, and the first examining this association with a leptin-to-adiponectin ratio. Our results provide support for the possibility that metabolic proteins at birth forecast risk for mental health symptoms in early childhood.

Applied relaxation and cortisol secretion: findings from a randomized controlled indicated prevention trial in adults with stress, anxiety, or depressive symptoms

Previous research has shown that relaxation interventions can reduce distress, anxiety, and depression. The exact mechanisms that underlie the efficacy of relaxation interventions remain unresolved. This study aimed to investigate whether applied relaxation (AR) leads to changes in cortisol secretion and whether these effects mediate fewer symptoms due to AR. Data come from a randomized controlled preventive interventional trial (N = 277) with elevated tension/distress, anxiety, or depressive symptomatology. Participants were randomized to an intervention group (IG; n = 139, received AR training), or a non-interventional control group (CG, n = 138). Psychopathological symptoms were assessed with DASS-21 and diagnoses of mental disorders via DIA-X-5. Cortisol was measured as short-term index in saliva (six times/d for 2 d at pre-, post-, and follow-up [FU] assessment) and long-term index in hair samples (once at pre-assessment and FU, respectively). Data were analyzed as pre-specified secondary analyses of the randomized controlled trial (RCT) on completer basis (n = 134 CG, n = 102 IG), using multivariable-adjusted linear regression models and mediation analyses (the DASS-21 change in the IG vs. CG with cortisol (area under the curve [AUC]) as mediator). From pre- to post-assessment, total daily salivary cortisol (AUC) decreased more strongly in the IG vs. CG (β-coefficient: -13.83, 95% confidence interval [CI]: -26.85 to -0.81), but was rendered non-significant when adjusting for pre-assessment AUC. This effect was not found for the cortisol awakening response (CAR) or hair cortisol. There was no evidence for a mediation of cortisol (AUC). These findings provide little support for the idea that cortisol reductions explain the beneficial effects of AR on mental health.

Osteopathic Manipulative Treatment as an Intervention to Reduce Stress, Anxiety, and Depression in First Responders: A Pilot Study

In this pilot study, we examined the efficacy of Osteopathic Manipulative Treatment (OMT) for improving symptoms of stress, anxiety, and depression (SAD) to determine a correlation between overall improvement in health and quality of life for first responders. Participants received weekly OMT or sham OMT targeting autonomic imbalance. Indicators of SAD were examined pre- and post-study. Overall, this pilot study suggests improvement in both the social-psychological (mental) self-assessments, and alterations in SAD-associated biomarkers from OMT.

Polymorphisms in the FKBP5 gene are associated with attention deficit and hyperactivity disorder in Korean children

Attention deficit hyperactivity disorder (ADHD) is a common and heritable childhood psychiatric disorder. Recently, many studies reported a down-regulated hypothalamus-pituitary-adrenal axis (HPA-axis) with low cortisol levels in children with ADHD. The FK506 binding protein 5 or FKBP5 gene regulates the negative feedback of the HPA-axis, and genetic variants in this gene showed an association with ADHD. We investigated the genetic association between FKBP5 gene polymorphisms and susceptibility to ADHD in Korean children. We conducted a case-control study with 150 ADHD children and 322 controls. Genotyping of FKBP5 rs9394309 and rs7748266 was performed by using polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP). Our results showed that rs7748266 polymorphism has significant genotype (p = 0.021) and allele (p = 0.009) frequency differences between children with ADHD and the control group. CT genotype [odds ratio (OR) 1.70, 95 % confidence interval (CI) 1.134-2.540, p = 0.010] and T allele (OR 1.54, 95 % CI 1.114-2.117, p = 0.009) were associated with increased risk of ADHD. In addition, dominant (p = 0.006) and over-dominant genetic (p = 0.016) models showed significant associations with ADHD. In the stratified analysis, a significant result was obtained from the girl samples (p = 0.048). The OR of the girls with ADHD with CT genotype was 2.29 (95 % CI 1.170-4.469, p = 0.014). In contrast to rs7748266 polymorphism, rs9394309 polymorphism did not show any significant result (p > 0.05). Haplotype analysis also revealed a significant difference of the TG haplotype for rs7748266 - rs9394309 (p = 0.028, global haplotype association p-value of 0.0091). Conclusively, we confirmed that FKBP5 gene polymorphisms were associated with ADHD in Korean children. These results suggested that FKBP5 may factor in the development of ADHD.

Maternal Prenatal Hair Cortisol Is Associated with Child Wheeze among Mothers and Infants with Tobacco Smoke Exposure and Who Face High Socioeconomic Adversity

The association of co-occurring prenatal stress and tobacco exposures on childhood wheezing and asthma are not well established. In this study, we compared maternal prenatal hair cortisol concentration (HCC) to the maternal report of infant wheezing (y/n) in the first year of life among mother-infant dyads exposed to tobacco smoke and socioeconomic adversity. Data were obtained from the Vitamin C to Decrease Effects of Smoking in Pregnancy on Infant Lung Function study. Maternal adversity was defined by the level of education, household income, and health insurance provider. Hair was collected at delivery, representing average circulating third-trimester cortisol levels. HCC was log transformed and dichotomized into high/low cortisol groups that were placed into a multivariate model predicting wheeze. Subjects (n = 132) were primarily White with ≤high school education and receiving government-provided health insurance. Forty-five percent of infants wheezed. Average HCC was 3.39 pg/mg hair. Women with HCC > 3.55 pg/mg were more than twice as likely to report having a child who wheezed (odds ratio 2.56, 95% confidence interval 1.22-5.40; p = 0.01), adjusting for insurance provider and maternal asthma. Among this sample of dyads with prenatal smoke exposure, elevated maternal HCC was associated with child wheeze that was not diminished after consideration of covariates.

Longitudinal Trajectories of Hair Cortisol: Hypothalamic-Pituitary-Adrenal Axis Dysfunction in Early Childhood

The objective of this study was to examine if longitudinal trajectories of hair cortisol concentrations (HCC) measured at two or three yearly time points can identify 1-3 year old children at risk for altered hypothalamic-pituitary-adrenal (HPA)-axis function due to early life stress (ELS). HCC was measured (N = 575) in 265 children using a validated enzyme-linked immunosorbent assay. Hair was sampled in Clinic Visits (CV) centered at years 1, 2, and 3 (n = 45); 1 and 2 (n = 98); 1 and 3 (n = 27); 2 and 3 (n = 95). Log-transformed HCC values were partitioned using latent class mixed models (LCMM) to minimize the Bayesian Information Criterion. Multivariable linear mixed effects models for ln-HCC as a function of fixed effects for age in months and random effects for participants (to account for repeated measures) were generated to identify the factors associated with class membership. Children in Class 1 (n = 69; 9% Black) evidenced declining ln-HCC across early childhood, whereas Class 2 members (n = 196; 43% Black) showed mixed trajectories. LCMM with only Class 2 members revealed Class 2A (n = 17, 82% Black) with sustained high ln-HCC and Class 2B (n = 179, 40% Blacks) with mixed ln-HCC profiles. Another LCMM limited to only Class 2B members revealed Class 2B1 (n = 65, 57% Black) with declining ln-HCC values (at higher ranges than Class 1), and Class 2B2 (n = 113, 30% Black) with sustained high ln-HCC values. Class 1 may represent hair cortisol trajectories associated with adaptive HPA-axis profiles, whereas 2A, 2B1, and 2B2 may represent allostatic load with dysregulated profiles of HPA-axis function in response to varying exposures to ELS. Sequential longitudinal hair cortisol measurements revealed the allostatic load associated with ELS and the potential for developing maladaptive or dysregulated HPA-axis function in early childhood.

The Role of the Circadian System in Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental condition characterised by the core symptoms of inattention, impulsivity and hyperactivity. Similar to many other neuropsychiatric conditions, ADHD is associated with very high levels of sleep disturbance. However, it is not clear whether such sleep disturbances are precursors to, or symptoms of, ADHD. Neither is it clear through which mechanisms sleep and ADHD are linked. One possible link is via modulation of circadian rhythms. In this chapter we overview the evidence that ADHD is associated with alterations in circadian processes, manifesting as later chronotype and delayed sleep phase in ADHD, and examine some mechanisms that may lead to such changes. We also interrogate how the circadian clock may be a substrate for therapeutic intervention in ADHD (chronotherapy) and highlight important new questions to be addressed to move the field forward.

Intrabladder PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in Mice Exposed to Repeated Variate Stress (RVS)

Stress causes symptom exacerbation in functional disorders of the urinary bladder. However, the potential mediators and underlying mechanisms of stress effects on micturition reflex function are unknown. We have characterized PACAP (Adcyap1) and PAC1 receptor (Adcyap1r1) signaling in stress-induced urinary bladder dysfunction in mice. We determined PACAP and PAC1 transcripts and protein expressions in the urinary bladder and lumbosacral dorsal root ganglia (DRG) and spinal cord in repeated variate stress (RVS) or control mouse (handling only) groups. RVS in mice significantly (p ≤ 0.01) increased serum corticosterone and urinary bladder NGF content and decreased weight gain. PACAP and PAC1 mRNA and protein were differentially regulated in lower urinary tract tissues with changes observed in lumbosacral DRG and spinal cord but not in urinary bladder. RVS exposure in mice significantly (p ≤ 0.01) increased (2.5-fold) voiding frequency as determined using conscious cystometry. Intrabladder administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased infused volume (1.5-2.7-fold) to elicit a micturition event and increased the intercontraction interval (i.e., decreased voiding frequency) in mice exposed to RVS and in control mice, but changes were smaller in magnitude in control mice. We also evaluated the effect of PAC1 blockade at the level of the urinary bladder on pelvic sensitivity in RVS or control mouse groups using von Frey filament testing. Intrabladder administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity following RVS. PACAP/receptor signaling in the CNS and PNS contributes to increased voiding frequency and pelvic sensitivity following RVS and may represent a potential target for therapeutic intervention.

The association between adversity and hair cortisol levels in humans: A meta-analysis

Adverse life events are associated with a constellation of negative health outcomes. Theory and research suggest that the hypothalamic-pituitary-adrenal (HPA) axis acts as one mechanism connecting adverse experiences with negative health outcomes. However, this relation is complicated by the potential for adversity to be associated with both hyperactivity and hypoactivity of the HPA axis, as assessed in both animal and human studies. Over the past decade, methodological advances have enabled the sampling of cortisol stored in hair, which provides a marker of HPA axis activity over a several-month period. The present meta-analysis included 28 studies to assess the strength and direction of the relation between adverse experiences and hair cortisol levels. Analyses were conducted using multilevel modeling (MLM) to quantify the magnitude of effects and mixture modeling to identify distinct subgroups of studies. Results of MLM analyses indicated that the overall effect size was small but significant d = 0.213, 95% CI [0.034, 0.397]. There was also significant between-study variance (τ = 0.155, 95% CI [0.065, 0.367]). Mixture modeling to identify distinct classes of studies based on effect size and direction resulted in a 2-class model: The first class included four studies with an overall negative and moderate effect size (d = -0.478, 95% CI [-0.639, -0.318]), and the second class included the remaining 24 studies with an overall positive and significant, albeit small, effect size (d = 0.141, 95% CI [0.084, 0.199]). Moderator analyses indicated that the strength and direction of the association between adversity and hair cortisol were moderated by features of the adversity exposure (e.g., type of adversity, timing of adversity), characteristics of the samples (e.g., clinical status, racial distribution), and features of the publication (e.g., publication type, geographic region of study). The findings refine our understanding of the long-term impact of adversity on dysregulation of the HPA axis, particularly as reflected in hair cortisol measures.

Chronic exposure to inhaled, traffic-related nitrogen dioxide and a blunted cortisol response in adolescents

BACKGROUND

Chronic health effects of traffic-related air pollution, like nitrogen dioxide (NO₂), are well-documented. Animal models suggested that NO₂ exposures dysregulate cortisol function.

OBJECTIVES

We evaluated the association between traffic-related NO₂ exposure and adolescent human cortisol concentrations, utilizing measures of the cortisol diurnal slope.

METHODS

140 adolescents provided repeated salivary cortisol samples throughout one day. We built a land use regression model to estimate chronic NO₂ exposures based on home and school addresses. We then generated model-based estimates of the association between cortisol and NO₂ exposure one year prior to cortisol sampling, examining changes in cortisol diurnal slope. The final model was adjusted other criteria pollutants, measures of psychosocial stress, anthropometry, and other demographic and covariates.

RESULTS

We observed a decrease in diurnal slope in cortisol for adolescents exposed to the estimated 75th percentile of ambient NO₂ (high exposure) relative to those exposed at the 25th percentile (low exposure). For a highly exposed adolescent, the log cortisol was lower by 0.06 µg/dl at waking (95% CI: -0.15, 0.02), 0.07 µg/dl at 30 min post waking (95% CI: -0.15, 0.02), and higher by 0.05 µg/dl at bedtime (95% CI: 0.05, 0.15), compared to a low exposed adolescent. For an additional interquartile range of exposure, the model-based predicted diurnal slope significantly decreased by 0.12 (95% CI: -0.23, -0.01).

CONCLUSIONS

In adolescents, we found that increased, chronic exposure to NO₂ and the mixture of pollutants from traffic sources was associated with a flattened diurnal slope of cortisol, a marker of an abnormal cortisol response which we hypothesize may be a mechanism through which air pollution may affect respiratory function and asthma in adolescents.

Examining Morning HPA Axis Activity as a Moderator of Hostile, Over-reactive Parenting on Children's Skills for Success in School

This study examined children's morning HPA axis activation as a moderator of links between hostile, over-reactive parenting at age 4.5 years and children's skills for success in school (higher executive function and literacy, and less externalizing behavior) at age 6. Participants included 361 adoptive families. Parenting was self-reported. HPA axis activation was measured by basal levels in morning cortisol. Executive function and literacy were assessed via standardized tasks. Externalizing behavior was reported by teachers. Results indicated that hostile, over-reactive parenting predicted more externalizing behavior and lower executive functioning regardless of children's morning HPA axis activation. HPA axis activation moderated the effects of hostile, over-reactive parenting on literacy. Among children with moderate to high morning HPA axis activation (approximately 60% of the sample), harsh parenting was linked with lower literacy; children with low morning HPA axis activation exhibited better literacy in the context of more hostile, over-reactive parenting. Yet, across the sample, hostile, over-reactive parenting remained in the low to moderate range, not in the high range. Findings are discussed in the context of considering not only whether children's stress system activation moderates responses to their environments, but also how these processes operate for different developmental outcomes.

Perceived stress moderates the effects of a randomized trial of dance movement therapy on diurnal cortisol slopes in breast cancer patients

Women with breast cancer are at risk of psychosocial distress and may suffer from aberrant diurnal cortisol rhythms. Dance movement therapy (DMT), a movement-based psychotherapy that incorporates exercise and artistic components, has demonstrated stress reduction effects. This study examined the effects of DMT on the diurnal cortisol rhythms of breast cancer patients undergoing radiotherapy treatment and the role of perceived stress in producing such effects. The study sample comprised 121 Chinese breast cancer patients randomized to the DMT (n=63) and control (n=58) groups. The intervention consisted of six 1.5-h group sessions held twice weekly over the course of radiotherapy. Participants completed validated self-report measures of perceived stress, fatigue, pain, and sleep disturbance and provided five salivary cortisol samples at baseline (Time 1) and post-intervention (Time 2). Moderated mediation analysis was used to evaluate the intervention effect on Time 2 diurnal cortisol slopes. Despite the absence of a significant DMT effect on diurnal cortisol slopes (B=-0.55, 95% CI=-1.20 to 0.08, β=-0.14), baseline perceived stress significantly moderated the intervention effect (B=-0.18, 95% CI=-0.32 to -0.05, β=-0.30). At high levels of baseline perceived stress (1 SD above the mean), the DMT group showed a steeper cortisol slope (M=-7.14) than the control group (M=-5.80) at Time 2. The present findings suggest that DMT might have a beneficial effect on diurnal cortisol slopes in breast cancer patients with high levels of distress.

Early Life Stress and Childhood Aggression: Mediating and Moderating Effects of Child Callousness and Stress Reactivity

Early life stress (ELS) has been implicated in the development of aggression, though the exact mechanisms remain unknown. This study tested associations between ELS, callousness, and stress reactivity in the prediction of school-age and persistent early childhood aggression. A longitudinal sample of 185 mother-child dyads completed a lab visit and mothers completed an online follow-up when children were preschool-aged and school-aged, respectively. Physiological and behavioral measures of stress reactivity were collected during the preschool period. Ratings of child aggressive behavior, ELS, and callousness were collected as well. The results suggested that ELS was related to measures of both school-age and persistent early childhood aggression, and that callousness had a mediating role in this process. Cortisol reactivity also moderated the association between ELS and persistent childhood aggression, such that the ELS-aggression relationship was stronger among children who had higher levels of cortisol reactivity during the preschool period. Clinical implications are discussed.

PACAP/Receptor System in Urinary Bladder Dysfunction and Pelvic Pain Following Urinary Bladder Inflammation or Stress

Complex organization of CNS and PNS pathways is necessary for the coordinated and reciprocal functions of the urinary bladder, urethra and urethral sphincters. Injury, inflammation, psychogenic stress or diseases that affect these nerve pathways and target organs can produce lower urinary tract (LUT) dysfunction. Numerous neuropeptide/receptor systems are expressed in the neural pathways of the LUT and non-neural components of the LUT (e.g., urothelium) also express peptides. One such neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the LUT. Mice with a genetic deletion of PACAP exhibit bladder dysfunction and altered somatic sensation. PACAP and associated receptors are expressed in the LUT and exhibit neuroplastic changes with neural injury, inflammation, and diseases of the LUT as well as psychogenic stress. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency in preclinical animal models and transgenic mouse models that mirror some clinical symptoms of bladder dysfunction. A change in the balance of the expression and resulting function of the PACAP/receptor system in CNS and PNS bladder reflex pathways may underlie LUT dysfunction including symptoms of urinary urgency, increased voiding frequency, and visceral pain. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction.

Increased cortisol awakening response after completing the summer treatment program in children with ADHD

OBJECTIVE

Little is known about the cortisol awakening response (CAR) in children with attention deficit hyperactivity disorder (ADHD). Here, we examined the CAR in children with ADHD and their mothers before, immediately after, and 4months after an intensive summer treatment program (STP).

METHODS

Participants were 37 children aged 7-12years who completed the STP in 2009 and 2010, and their mothers. Daily saliva samples for cortisol measurement were collected twice daily at awakening and 30min afterwards at pre-STP, post-STP, and during a follow-up measurement period. ADHD symptom scores were evaluated by parents, and participants completed the Kid-KINDL^R QOL questionnaire.

RESULTS

CAR was low in children with ADHD before the STP, and increased to the control range 4months after STP. Maternal CAR also tended to increase after STP. Changes in the CAR in children tended to correlate with an improved ADHD inattention scores (p=0.091), physical health (p=0.070), and school life subscales scores in the Kid-KINDL^R (p=0.079).

CONCLUSION

We demonstrated that STP improved the behavior and QOL of children with ADHD. Our results indicate that STP could lead to improvements in HPA axis function, as reflected by increased CAR after STP.

Associations between diurnal cortisol patterns and lifestyle factors, psychotic symptoms, and neurological deficits: A longitudinal study on patients with chronic schizophrenia

The present study examined the relationships between diurnal cortisol patterns and perceived stress, lifestyle factors, psychotic symptoms, neurological deficits, and daily functioning in patients with chronic schizophrenia. The participants were 149 Chinese patients with chronic schizophrenia, who provided salivary cortisol measures upon waking, before lunchtime, and before bedtime at baseline (Time 1). Self-report measures on perceived stress and lifestyle factors such as body-mass index and daily exercise span were recorded at Time 1. Diagnostic assessments on psychotic symptoms, neurological deficits, and daily functioning were made at Time 1 and Time 2 (3 months later). Latent growth modeling and path modeling analysis were performed to investigate the diurnal cortisol patterns and the relationships with the study variables, respectively. Greater perceived stress and body-mass index and less physical activity were significantly linked to reduced cortisol decline. Reduced cortisol decline at Time 1 significantly predicted greater psychotic (positive and negative) symptoms and more severe neurological deficits in motor coordination and sequencing of complex motor acts at Time 2. The present results contribute to a better understanding of the diurnal cortisol patterns among chronic schizophrenia patients and the associations with lifestyle factors, psychotic symptoms, and neurological deficits. The findings lend support to the neural diathesis-stress model and suggest that hypothalamic-pituitary-adrenal axis may potentially mediate the effects of lifestyle factors on psychotic symptoms and neurological deficits.

Pediatric Obesity Empowerment Model Group Medical Visits (POEM-GMV) as Treatment for Pediatric Obesity in an Underserved Community

BACKGROUND

This is a retrospective cohort study to evaluate a novel group medical visit (GMV) program using an empowerment curriculum as treatment for pediatric obesity in a federally qualified community health center.

METHODS

Biometric and self-reported data were reviewed from 417 overweight or obese children ages 5-18 attending the pediatric obesity empowerment model GMV program (POEM-GMV) at least twice during a 3-year period. Variables were evaluated using paired means t-test. Pearson's correlation test was used to evaluate variables and the BMI z-score. Subanalysis by gender was performed.

RESULTS

The average participant was 10.48 ± 2.53 years old and participated for 301 ± 287 days. BMI z-score reduced from 2.99 ± 0.96 to 2.88 ± 0.88 (p < 0.0001). Overall, 62.6% of participants had improved weight outcome. Statistically significant improvement was noted in stress, exercise, beverage consumption, fast food intake, television viewing, and bedtime. Stress and beverage consumption had the highest correlation with BMI z-score. By sex, 71.4% of boys (n = 196; p < 0.0001) and 54.8% (n = 221; p < 0.014) of girls realized a reduction in BMI z-score, 61.2% (p < 0.001) of boys and 47.1% (p = 0.097) of girls had a reduction in their percent overweight.

CONCLUSIONS

POEM-GMV may be a useful approach in the treatment of pediatric obesity in an underserved community. There were statistically significantly improved outcomes in obesity, especially for boys. Significant improvement was observed in many lifestyle factors associated with obesity. Weight loss most closely correlated with reduced stress levels and sugary beverage consumption. Additional studies are needed to further evaluate the efficacy of POEM-GMV.

Summary cortisol reactivity indicators: Interrelations and meaning

Research on the hypothalamic pituitary adrenal (HPA) axis has involved a proliferation of cortisol indices. We surveyed recently published HPA-related articles and identified 15 such indices. We sought to clarify their biometric properties, specifically, how they interrelate and what they mean, because such information is rarely offered in the articles themselves. In the present article, the primary samples consist of community mothers and their infants (N = 297), who participated in two challenges, the Toy Frustration Paradigm and the Strange Situation Procedure. We sought to cross-validate findings from each of these samples against the other, and also against a clinically depressed sample (N = 48) and a sample of healthy older adults (N = 51) who participated in the Trier Social Stress Test. Cortisol was collected from all participants once before and twice after the challenges. These heterogenous samples were chosen to obtain the greatest possible range in cortisol levels and stress response regulation. Using these data, we computed the 15 summary cortisol indices identified in our literature survey. We assessed inter-relations amongst indices and determined their underlying dimensions via principal component analysis (PCA). The PCAs consistently extracted two components, accounting for 79%–93% of the variance. These components represent “total cortisol production” and “change in cortisol levels.” The components were highly congruent across challenge, time, and sample. High variable loadings and explained factor variance suggest that all indices represent their underlying dimensions very well. Thus the abundance of summary cortisol indices currently represented in the literature appears superfluous.

Pubertal maturation and cortisol level in response to a novel social environment among female adolescents

Research indicates changes in HPA-axis activity across puberty. The current study extends existing work by evaluating pubertal status and cortisol level in a novel social environment (research laboratory) while controlling for several important biological, behavioral, and psychological variables. Participants were 30 girls (ages 9-16 years) from the United States. Pubertal status was assessed via the Pubertal Development Scale. Salivary samples were collected at laboratory-introduction and a matched at-home period; laboratory-introduction levels were regressed on basal cortisol levels to create standardized residual scores. After controlling for covariates, pubertal status was positively associated with residualized cortisol values. Findings indicate more advanced puberty related to greater cortisol response to the laboratory; data are discussed in terms of future research and building biopsychosocial models of the puberty-psychopathology linkage.

Effects of parental depressive symptoms on child adjustment moderated by hypothalamic pituitary adrenal activity: within- and between-family risk

Child hypothalamic pituitary adrenal (HPA) activity was investigated as a moderator of parental depressive symptom effects on child behavior in an adoption sample (n = 210 families). Adoptive parents' depressive symptoms and child internalizing and externalizing were assessed at 18, 27, and 54 months, and child morning and evening HPA activity measured through salivary cortisol at 54 months. Children's daily cortisol levels and day-to-day variability were tested as moderators of longitudinal associations between parent and child symptoms at within- and between-family levels. Mothers' symptoms related directly to child internalizing, but child evening cortisol moderated effects of fathers' symptoms on internalizing, and of both parents' symptoms on externalizing. Different paths of within-family risk dynamics versus between-family risk synergy were found for internalizing versus externalizing outcomes.

The Healthy Start project: a randomized, controlled intervention to prevent overweight among normal weight, preschool children at high risk of future overweight

BACKGROUND

Research shows that obesity prevention has to start early. Targeting interventions towards subgroups of individuals who are predisposed, but yet normal weight, may prove more effective in preventing overweight than interventions towards unselected normal weight subsets. Finally, interventions focused on other factors than diet and activity are lacking. The objectives were to perform a randomized, controlled intervention aiming at preventing overweight in children aged 2-6 years, who are yet normal weight, but have high predisposition for future overweight, and to intervene not only by improving diet and physical activity, but also reduce stress and improve sleep quality and quantity.

METHODS/DESIGN

Based on information from the Danish National Birth Registry and administrative birth forms, children were selected based on having either a high birth weight, a mother who was overweight prior to pregnancy, or a familial low socioeconomic status. Selected children (n = 5,902) were randomized into three groups; an intervention group, a shadow control group followed in registers exclusively, and a control group examined at the beginning and at the end of the intervention. Approximately 21% agreed to participate. Children who presented as overweight prior to the intervention were excluded from this study (n = 92). In the intervention group, 271 children were included, and in the control group 272 were included. Information obtained from the shadow control group is on-going, but it is estimated that 394 children will be included. The intervention took place over on average 1½ year between 2009 and 2011, and consisted of optional individual guidance in optimizing diet and physical activity habits, reducing chronic stress and stressful events and improving sleep quality and quantity. The intervention also included participation in cooking classes and play arrangements. Information on dietary intake, meal habits, physical activity, sleep habits, and overall stress level was obtained by 4-7 day questionnaire diaries and objective measurements.

DISCUSSION

If the Healthy Start project is effective in preventing excessive weight gain, it will provide valuable information on new determinants of obesity which should be considered in future interventions, and on new strategies to prevent development of overweight and obesity at an early age.

Growth delay as an index of allostatic load in young children: predictions to disinhibited social approach and diurnal cortisol activity

The goal of this study was to examine whether growth delay can serve as an index of allostatic load during early development, as it is well known that the activity of stress-mediating systems inhibits growth. The participants were children adopted internationally from institutional care (n = 36), children adopted internationally from foster care (n = 26), and nonadopted children (n = 35). For the adopted children, height for age and weight for height were assessed at adoption; for all children, disinhibited social approach (DSA; termed elsewhere as "indiscriminate friendliness") and diurnal cortisol were assessed at 6-8 years (M = 6.9 years). For internationally adopted children in general, and postinstitutionalized children specifically, linear growth delay assessed at the time of adoption was associated with more dysregulated behavior in response to an unfamiliar adult (i.e., greater DSA) and a more dysregulated diurnal cortisol rhythm (i.e., higher late afternoon and evening values). Further, among the most growth-delayed children, higher cortisol levels later in the day were correlated with DSA. The potential for using growth delay as an allostatic load indicator and the possible problems and limitations in its use in child populations are discussed.

Hypothalamic-pituitary-adrenal axis activity and upper respiratory tract infection in young children transitioning to primary school

RATIONALE

We have previously reported an increase in salivary cortisol in a cohort of 4-year-old children transitioning to primary school. We hypothesised that increased cortisol in response to this acute naturalistic stress in early development may be immunostimulatory and associated with positive health outcomes.

OBJECTIVES

We tested this hypothesis by measuring upper respiratory tract infection (URI) across the first 6 months of school, in relation to salivary cortisol at the end of the second week following school transition

METHODS

Seventy children supplied morning and evening saliva samples for cortisol assay. Children were psychologically assessed for temperament and behavioural adaptation. Symptoms of URI were recorded in diary form, and variables relating to URI occurrence, duration and severity were assessed.

RESULTS

Children with higher evening cortisol at school transition experienced significantly fewer episodes of URI over the following 6 months. Diurnal cortisol change was negatively correlated with number of illnesses across the 6 months, indicating an association between a greater decline in cortisol across the day and a greater number of colds. URI severity was associated with the greatest resistance to URI infection in children who were less socially isolated and who had a smaller diurnal change in cortisol across the day.

CONCLUSIONS

Our results showing that higher cortisol is associated with lower URI may be explained by proposing that increased cortisol in response to the naturalistic stress of school transition may prime the immune system to develop resistance to URI at this critical stage of a child's development.

How might stress contribute to increased risk for schizophrenia in children with chromosome 22q11.2 deletion syndrome?

The most common human microdeletion occurs at chromosome 22q11.2. The associated syndrome (22q11.2DS) has a complex and variable phenotype with a high risk of schizophrenia. While the role of stress in the etiopathology of schizophrenia has been under investigation for over 30 years (Walker et al. 2008), the stress–diathesis model has yet to be investigated in children with 22q11.2DS. Children with 22q11.2DS face serious medical, behavioral, and socioemotional challenges from infancy into adulthood. Chronic stress elevates glucocorticoids, decreases immunocompetence, negatively impacts brain development and function, and is associated with psychiatric illness in adulthood. Drawing knowledge from the extant and well-developed anxiety and stress literature will provide invaluable insight into the complex etiopathology of schizophrenia in people with 22q11.2DS while suggesting possible early interventions. Childhood anxiety is treatable and stress coping skills can be developed thereby improving quality of life in the short-term and potentially mitigating the risk of developing psychosis.

Childhood trauma is associated with hypothalamic-pituitary-adrenal axis responsiveness in irritable bowel syndrome

BACKGROUND & AIMS

A history of early adverse life events (EALs) is associated with a poorer outcome and higher levels of distress in adult patients with functional gastrointestinal disorders. An EAL is thought to predispose individuals to develop a range of chronic illnesses by inducing persistent changes in the central stress response systems, including the hypothalamic-pituitary-adrenal (HPA) axis. We sought to determine if EALs affect the HPA axis response to a visceral stressor in irritable bowel syndrome (IBS) patients and healthy controls, and to determine if this is affected by sex or related to symptoms or quality of life.

METHODS

Forty-four IBS patients (25 women, 19 men) and 39 healthy controls (21 women, 18 men) were assessed for gastrointestinal and psychological symptoms and EALs by validated questionnaires and interview. All subjects underwent a visceral stressor (sigmoidoscopy). Salivary cortisol was collected at baseline and serially for 1 hour poststressor.

RESULTS

Twenty-one IBS patients and 18 controls had EALs. In subjects with and without IBS, an EAL was associated with higher mean (+/-SD) cortisol levels (0.32 +/- 0.2 vs 0.20 +/- 0.1 microg/dL; P = .003) and higher area under the curve (28.1 +/- 17 vs 18.6 +/- 13 microg x min/dL; P = .005) after the stressor compared with subjects without EALs. In IBS, a faster resolution of cortisol to basal values corresponded to lower symptom severity (r = -0.36, P < .05) and better disease-specific quality of life (r = 0.33, P < .05).

CONCLUSIONS

HPA axis hyperresponsiveness to a visceral stressor is related more to a history of EALs than to the presence of IBS. However, HPA axis reactivity has a moderating effect on IBS symptoms.

Diurnal patterns of salivary cortisol across the adolescent period in healthy females

When examining the diurnal profile of the hormone cortisol in children and adolescents developmental issues are particularly relevant. Previous findings regarding relationships between cortisol secretory activity and reproductive (pubertal) maturation lack clarity and may reflect methodological inconsistencies between studies. This study examined the diurnal cortisol profile across female adolescence, with a particular focus on an obvious and unique marker of development: menarche. In a cross-sectional design, 61 healthy female adolescents aged 9-18 years (mean age 13.89 years, S.D.+/-2.72) collected eight saliva samples per day on two consecutive weekdays. Samples were collected at awakening, 15, 30 and 45min and 3, 6, 9 and 12h post-awakening in order to capture both the cortisol awakening response (CAR) and the subsequent period of decline. Demographic information was recorded and participants also completed the Spielberger State-Trait Anxiety Inventory. Patterns of cortisol secretion exhibited good intra-individual stability across the two sampling days. Participants evidenced a robust diurnal pattern, with cortisol levels peaking approximately 30-45min post-awakening (the CAR) and steadily declining concentrations over the remainder of the day. Differences according to developmental status (in terms of whether or not participants had experienced first menses: menarche) were observed in the time of peak secretion of the CAR, and these distinct patterns could not be accounted for by group differences in demographic, situational or psychological characteristics measured in this study. This effect for the CAR was associated with the onset of menarche alone, unlike cortisol levels over the remainder of the day. For those who had undergone menarche, were older and of greater BMI, cortisol levels remained higher over the day. There was a significant difference in cortisol concentrations at 6h post-awakening between pre- and post-menarche groups. Again, these differences in daytime cortisol secretory activity could not be attributed to situational or psychological factors. Establishing patterns of cortisol secretion in healthy female adolescents provides an important baseline from which to investigate hypothalamic-pituitary-adrenal (HPA) physiology, measured via salivary cortisol, in adolescent populations with known or suspected psychopathology.

BDNF Val66Met polymorphism is associated with HPA axis reactivity to psychological stress characterized by genotype and gender interactions

BACKGROUND

A key protein in maintaining neuronal integrity throughout the life span is brain-derived neurotrophic factor (BDNF). The BDNF gene is characterized by a functional polymorphism, which has been associated with stress-related disorders such as anxiety-related syndromes and depression, prompting us to examine individual responses by Genotype and Sex to a standardized social stress paradigm. Gender differences in BDNFxstress responses were posited because estrogen induces synthesis of BDNF in several brain regions.

METHODS

97 university students (51 females and 46 males) participated in a social stress procedure (Trier Social Stress Test, TSST). Indices of stress were derived from repeated measurement of cortisol, blood pressure, and heart rate during the TSST. All subjects were genotyped for the Val66Met polymorphism.

RESULTS

Tests of within-subject effects showed a significant three-way interaction (SPSS GLM repeated measures: Time (eight levels)xBDNF (val/val, val/met)xSex: p=0.0002), which reflects gender differences in the pattern of cortisol rise and decline during the social challenge. In male subjects, val/val homozygotes showed a greater rise in salivary cortisol than val/met heterozygotes. In female subjects, there was a trend for the opposite response, which is significant when area under the curve increase (AUCi) was calculated for the val/val homozygotes to show the lowest rise. Overall, the same pattern of results was observed for blood pressure and heart rate.

CONCLUSIONS

These results indicate that a common, functionally significant polymorphism in the BDNF gene modulates HPA axis reactivity and regulation during the TSST differently in men and women. Findings may be related to gender differences in reactivity and vulnerability to social stress.

Psychological stress and obesity

OBJECTIVE

To examine whether there is a relationship between psychological stress in the family and obesity in 5- to 6-year-old children.

STUDY DESIGN

A total of 7443 Swedish families reported on psychological stress across 4 domains as part of the prospective All Babies in Southeast Sweden-project (ABIS). Domains assessed included serious life events, parenting stress, lack of social support, and parental worries. These variables were summarized in cross-sectional and longitudinal composite measures of psychological stress. Logistic regression models were used to calculate odds ratios for childhood obesity for psychological stress.

RESULTS

A total of 4.2% of the children were obese according to age-adjusted international standards. Children from families that reported stress in at least 2 of the 4 domains assessed had significantly higher adjusted odds ratios (OR) for obesity, both cross-sectionally (OR, 2.1; 95% CI, 1.3-3.5; P < .01) and longitudinally (OR, 2.6; 95% CI, 1.3-5.4, P < .01).

CONCLUSION

Psychological stress in the family may be a contributing factor for childhood obesity. This finding underscores how important it is to give children with obesity and their families psychological and social support in addition to recommendations about changing life style.

Cognitive performance and morning levels of salivary cortisol and alpha-amylase in children reporting high vs. low daily stress perception

The aim of the present study was to assess the effects of daily stress perception on cognitive performance and morning basal salivary cortisol and alpha-amylase levels in healthy children aged 9-12. Participants were classified by whether they had low daily perceived stress (LPS, n = 27) or a high daily perceived stress (HPS, n = 26) using the Children Daily Stress Inventory (CDSI). Salivary cortisol and alpha-amylase were measured at awakening and 30 minutes later. Cognitive performance was assessed using the Cognitive Drug Research assessment system. The HPS group exhibited significantly poorer scores on speed of memory (p < .05) and continuity of attention (p < .05) relative to the LPS group. The HPS group also showed significantly lower morning cortisol levels at awakening and at +30 minutes measures in comparison with the LPS group (p < .05), and mean morning cortisol levels were negatively correlated with speed of memory (p < .05) in the 53 participants. No significant differences were observed between both groups in alpha-amylase levels. These findings suggest that daily perceived stress in children may impoverish cognitive performance via its modulating effects on the HPA axis activity.

Stress and the hypothalamic pituitary adrenal axis in the developmental course of schizophrenia

Diathesis-stress models of schizophrenia and other psychotic disorders have dominated theorizing about etiology for over three decades. More recently, with advances in our understanding of the biological processes mediating the effects of stress, these models have incorporated mechanisms to account for the adverse impact of stress on brain function. This review examines recent scientific findings on the role of the hypothalamic-pituitary-adrenal (HPA) axis, one of the primary neural systems triggered by stress exposure, in the expression of vulnerability for schizophrenia. The results indicate that psychotic disorders are associated with elevated baseline and challenge-induced HPA activity, that antipsychotic medications reduce HPA activation, and that agents that augment stress hormone (cortisol) release exacerbate psychotic symptoms. The cumulative findings are discussed in light of a neural diathesis-stress model that postulates that cortisol has the potential to increase activity of dopamine pathways that have been implicated in schizophrenia and other psychotic disorders.

Developmental origins theory from prematurity to adult disease

Developmental Origins Theory has received little coverage in the nursing literature, even though it has received much attention in other sciences. The theory proposes that prenatal stress provokes adaptive changes in endocrine and metabolic processes that become permanently programmed and impact later adult health. This paper reviews the theory and describes the primary neuroendocrine mechanism of hypothalamic-pituitary-adrenal axis function. Supporting research evidence in preterm infant and adult samples is presented. Through knowledge of the theory and the long-term sequelae for preterm infants, nurses will have a different theoretical perspective and growing evidence to consider in their care for pregnant women and infants.

Stress hormones and immune function

Over the past 20 years we have demonstrated both in animal models and in human studies that stress increases neuroendocrine hormones, particularly glucocorticoids and catecholamines but to some extent also prolactin, growth hormone and nerve growth factor. We have also shown that stress, through the action of these stress hormones, has detrimental effects on immune function, including reduced NK cell activity, lymphocyte populations, lymphocyte proliferation, antibody production and reactivation of latent viral infections. Such effects on the immune system have severe consequences on health which include, but are not limited to, delayed wound healing, impaired responses to vaccination and development and progression of cancer. These data provide scientific evidence of the effects of stress on immune function and implications for health.

Selective transrepression versus transactivation mechanisms by glucocorticoid receptor modulators in stress and immune systems

Glucocorticoids control immune homeostasis and regulate stress responses in the human body to a large extent via the glucocorticoid receptor. This transcription factor can modulate gene expression either through direct DNA binding (mainly resulting in transactivation) or independent of DNA binding (in the majority of cases resulting in transrepression). The aim of this review is to discuss the mechanistic basis and applicability of different glucocorticoid receptor modulators in various affections, ranging from immune disorders to mental dysfunctions.

Inclusion of the glucocorticoid receptor in a hypothalamic pituitary adrenal axis model reveals bistability

BACKGROUND

The body's primary stress management system is the hypothalamic pituitary adrenal (HPA) axis. The HPA axis responds to physical and mental challenge to maintain homeostasis in part by controlling the body's cortisol level. Dysregulation of the HPA axis is implicated in numerous stress-related diseases.

RESULTS

We developed a structured model of the HPA axis that includes the glucocorticoid receptor (GR). This model incorporates nonlinear kinetics of pituitary GR synthesis. The nonlinear effect arises from the fact that GR homodimerizes after cortisol activation and induces its own synthesis in the pituitary. This homodimerization makes possible two stable steady states (low and high) and one unstable state of cortisol production resulting in bistability of the HPA axis. In this model, low GR concentration represents the normal steady state, and high GR concentration represents a dysregulated steady state. A short stress in the normal steady state produces a small perturbation in the GR concentration that quickly returns to normal levels. Long, repeated stress produces persistent and high GR concentration that does not return to baseline forcing the HPA axis to an alternate steady state. One consequence of increased steady state GR is reduced steady state cortisol, which has been observed in some stress related disorders such as Chronic Fatigue Syndrome (CFS).

CONCLUSION

Inclusion of pituitary GR expression resulted in a biologically plausible model of HPA axis bistability and hypocortisolism. High GR concentration enhanced cortisol negative feedback on the hypothalamus and forced the HPA axis into an alternative, low cortisol state. This model can be used to explore mechanisms underlying disorders of the HPA axis.