It's in your nature

Kevin Lewis

January 12, 2013

Human milk cortisol is associated with infant temperament

Katherine Grey et al.
Psychoneuroendocrinology, forthcoming

The implications of the biologically active elements in milk for the mammalian infant are largely unknown. Animal models demonstrate that transmission of glucocorticoids through milk influences behavior and modifies brain development in offspring. The aim of this study was to determine the relation between human milk cortisol levels and temperament of the breastfed infant. Fifty-two mother and infant pairs participated when the infants were three-months old. Milk cortisol levels were assessed and each mother completed the Infant Behavior Questionnaire (IBQ), a widely used parent-report measure of infant temperament. Analyses revealed a positive association between milk cortisol and the negative affectivity dimension of the IBQ (partial r = .37, p < .01). No correlation was found between elevated cortisol levels and the surgency/extraversion or the orienting/regulation dimensions. Further, the positive association between increased maternal milk cortisol and negative affectivity was present among girls (β = .59, p < .01), but not among boys. (Although, the sex by milk cortisol interaction term was not statistically significant, suggesting that these results require replication.) Environmental factors such as maternal demographics and negative maternal affect (depression and perceived stress) at the time of assessment did not account for the positive association. The findings support the proposal that exposure to elevated levels of cortisol in human milk influences infant temperament. The findings further suggest that mothers have the ability to shape offspring phenotype through the transmission of biologically active components in milk.


Stress and Neurodevelopmental Processes in the Emergence of Psychosis

Carrie Holtzman et al.
Neuroscience, forthcoming

The notion that stress plays a role in the etiology of psychotic disorders, especially schizophrenia, is longstanding. However, it is only in recent years that the potential neural mechanisms mediating this effect have come into sharper focus. The introduction of more sophisticated models of the interplay between psychosocial factors and brain function has expanded our opportunities for conceptualizing more detailed psychobiological models of stress in psychosis. Further, scientific advances in our understanding of adolescent brain development have shed light on a pivotal question that has challenged researchers; namely, why the first episode of psychosis typically occurs in late adolescence/young adulthood. In this paper, we begin by reviewing the evidence supporting associations between psychosocial stress and psychosis in diagnosed patients as well as individuals at clinical high risk for psychosis. We then discuss biological stress systems and examine changes that precede and follow psychosis onset. Next, research findings on structural and functional brain characteristics associated with psychosis are presented; these findings suggest that normal adolescent neuromaturational processes may go awry, thereby setting the stage for the emergence of psychotic syndromes. Finally, a model of neural mechanisms underlying the pathogenesis of psychosis is presented and directions for future research strategies are explored.


Longitudinal Relations Among Language Skills, Anger Expression, and Regulatory Strategies in Early Childhood

Caroline Roben, Pamela Cole & Laura Marie Armstrong
Child Development, forthcoming

Researchers have suggested that as children's language skill develops in early childhood, it comes to help children regulate their emotions (Cole, Armstrong, & Pemberton, 2010; Kopp, 1989), but the pathways by which this occurs have not been studied empirically. In a longitudinal study of 120 children from 18 to 48 months of age, associations among child language skill, observed anger expression, and regulatory strategies during a delay task were examined. Toddlers with better language skill, and whose language skill increased more over time, appeared less angry at 48 months and their anger declined more over time. Two regulatory strategies, support seeking and distraction, explained a portion of the variance in the association between language skill and anger expression after toddlerhood.


Exploring How Nature and Nurture Affect the Development of Reading: An Analysis of the Florida Twin Project on Reading

Sara Hart et al.
Developmental Psychology, forthcoming

Research on the development of reading skills through the primary school years has pointed to the importance of individual differences in initial ability as well as the growth of those skills. Additionally, it has been theorized that reading skills develop incrementally. The present study examined the genetic and environmental influences on 2 developmental models representing these parallel ideas, generalizing the findings to explore the processes of reading development. Participants were drawn from the Florida Twin Project on Reading, with a total of 2,370 pairs of twins representative of the state of Florida. Twins' oral reading fluency scores from school progress monitoring records collected in the fall of Grades 1-5 were used to model development. Results suggested that genetic influences on the development of reading are general, shared across the early school years, as well as novel, with new genetic influences introduced at each of the first 3 years of school. The shared environment estimates suggest a pattern of general influences only, suggesting environmental effects that are moderate and stable across development.


The scarring effect of unemployment throughout adulthood on psychological distress at age 50: Estimates controlling for early adulthood distress and childhood psychological factors

M. Daly & L. Delaney
Social Science & Medicine, forthcoming

Unemployment is an established predictor of psychological distress. Despite this robust relationship, the long-term impact of unemployment on human welfare has been examined in relatively few studies. In this investigation we test the association between the life-time duration of unemployment over a 34 year period from 1974 and 2008 and psychological distress at age 50 years in a sample of 6,253 British adults who took part in the National Child Development Study (NCDS). In addition to adjusting for demographic characteristics, we account for the role of childhood psychological factors, which have been shown to predict adult occupational and mental health outcomes and may determine the connection between unemployment and distress. We find that intelligence and behavioral/emotional problems at age 11 predict both unemployment and psychological distress later in life. Furthermore, as predicted, the duration of unemployment throughout adulthood was associated with elevated levels of psychological distress at age 50, after adjusting for demographic characteristics including labor force status at age 50. The emotional impact of unemployment was only marginally attenuated by the inclusion of childhood factors and early-life distress levels in the analyses. Thus, unemployment may lead to worsening distress levels that persist over time and which cannot be attributed to childhood or early-life well-being or cognitive functioning early in life. Our analysis further supports the idea of psychological scarring from unemployment and the importance of employment outcomes for adult well-being.


Associations between mental disorders and the common cold in adults: A population-based cross-sectional study

Yuki Adam, Gunther Meinlschmidt & Roselind Lieb
Journal of Psychosomatic Research, January 2013, Pages 69-73

Objective: To investigate the association between specific mental disorders and the common cold.

Methods: Negative binomial regression analyses were applied to examine cross-sectional associations of a broad range of mental disorders according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) employing the standardized Munich Composite International Diagnostic Interview, with the self-reported number of occurrences of the common cold during the past 12 months in a representative population sample of 4022 German adults aged 18-65 years.

Results: After adjustment for covariates including age, gender, and marital and socioeconomic status, having any 12-month DSM-IV mental disorder (incidence rate ratio [IRR] = 1.44, 95% confidence interval [CI] = 1.29-1.60), any substance abuse or dependence (IRR = 1.32, 95% CI = 1.14-1.52), possible psychotic disorder (IRR = 1.43, 95% CI = 1.09-1.87), any mood disorder (IRR = 1.35, 95% CI = 1.16-1.56), any anxiety disorder (IRR = 1.40, 95% CI = 1.23-1.59), or any somatoform disorder (IRR = 1.38, 95% CI = 1.18-1.62) was shown to be positively associated with the number of occurrences of a cold during the past 12 months.

Conclusion: The presence of a DSM-IV mental disorder was associated with a 44% higher risk of having experienced a cold in the past 12 months. Further studies are needed to explore potential common risk factors for incidence of mental disorders and the common cold, since the pathway connecting them has not been fully determined.


Heart Rate and Antisocial Behavior: Mediation and Moderation by Affiliation With Bullies. The TRAILS Study

Jelle Sijtsema et al.
Journal of Adolescent Health, January 2013, Pages 102-107

Purpose: Low heart rate (HR) has been linked to antisocial behavior (ASB). However, the effect of low HR may be mediated by affiliation with bullies. We hypothesized that individuals with low HR are more likely to affiliate with bullies and in turn are influenced by these peers.

Methods: Data come from two waves of a subsample of the TRAILS study (N = 809; 44.0% boys; mean age of 11.0 years at T1 and 13.5 years at T2). ASB was measured using the Antisocial Behavior Questionnaire at both waves. HR was assessed during rest at T1. Affiliation with bullies was assessed via peer nominations at T1. Possible gender differences were taken into account, and all analyses were adjusted for family context (i.e., family breakup and socioeconomic status).

Results: Regression analyses showed that lower HR was only associated with ASB in (pre)adolescents who affiliated with bullies. Moreover, the effect of lower HR on boys' ASB was partly mediated by affiliation with bullies.

Conclusions: Our findings show that (pre)adolescents, and in particular boys, seem to be in environments that match their biological disposition and in turn are shaped by this environment.


Effects of targeted self-coaching on applicant distortion of personality measures

Katherine Sliter & Neil Christiansen
Journal of Personnel Psychology, Fall 2012, Pages 169-175

The present study evaluated the impact of reading self-coaching book excerpts on success at faking a personality test. Participants (N = 207) completed an initial honest personality assessment and a subsequent assessment with faking instructions under one of the following self-coaching conditions: no coaching, chapters from a commercial book on how to fake preemployment personality scales, and personality coaching plus a chapter on avoiding lie-detection scales. Results showed that those receiving coaching materials had greater success in raising their personality scores, primarily on the traits that had been targeted in the chapters. In addition, those who read the chapter on avoiding lie-detection scales scored significantly lower on a popular impression management scale while simultaneously increasing their personality scores. Implications for the use of personality tests in personnel selection are discussed.


Nature, correlates, and consequences of stress-related biological reactivity and regulation in Army nurses during combat casualty simulation

Leigh McGraw et al.
Psychoneuroendocrinology, January 2013, Pages 135-144

This study examined the nature, concomitants, and consequences of stress-related biological reactivity and regulation among Army nurses. Saliva was collected, heart rate (HR) and blood pressure (BP) recorded from 38 Army nurses (74% female; mean age 28.5 years [SD = 6.5]) before, during, and after participation in the Combat Casualty Stress Scenario (CCSS). Saliva was assayed for cortisol and alpha-amylase (sAA). The CCSS simulates emergency combat rescue, employing two simulated combat casualties, aversive body odors, recorded battlefield sounds, and smoke in a low light environment. Participants locate and conduct preliminary assessments of the simulated patients, triage based on injury severity, initiate treatment, and coordinate medical evacuation by radio. Results revealed large magnitude increases in cortisol, sAA, HR, systolic BP and diastolic BP in response to the CCSS, followed by recovery to baseline levels 30 min after the task for all physiological parameters except cortisol. Age, gender, perceived difficulty of the CCSS, and previous nursing experience were associated with individual differences in the magnitude of the physiological responses. Lower levels of performance related to triage and treatment were associated with higher levels of reactivity and slower recovery for some of the physiological measures. The findings raise important questions regarding the utility of integrating measures of the psychobiology of the stress response into training programs designed to prepare first responders to handle highly complex and chaotic rescue situations.


Exposed intestines and contaminated cooks: Sex, stress, & satiation predict disgust sensitivity

Laith Al-Shawaf & David Lewis
Personality and Individual Differences, forthcoming

An evolutionary perspective predicts that the intensity of the disgust response should depend on the ancestral costs and benefits of coming into contact with disease vectors. Previous research advanced the compensatory behavioral prophylaxis hypothesis: progesterone-induced immunosuppression should be accompanied by increased disgust and contaminant-avoidance. However, extant data do not address whether factors other than progesterone-induced immunosuppression also trigger heightened disgust. The current study delineates two competing prophylaxis hypotheses and adjudicates between them by testing whether stress and satiation, which shift the costs and benefits of prophylactic behavior but are unrelated to progesterone-induced immunosuppression, predict disgust sensitivity. Results revealed a sex-stress-satiation interaction in predicting Disgust Scale-Revised (DS-R) scores. This study provides evidence of a broader system of compensatory prophylaxis, illuminates the functional basis of facultative shifts in disgust, and presents conceptual and statistical analyses for more cleanly cleaving the psychology of disgust at its natural joints.


Association of menstrual cycle phase with the core components of empathy

Birgit Derntl et al.
Hormones and Behavior, January 2013, Pages 97-104

Evidence has accumulated that emotion recognition performance varies with menstrual cycle phase. However, according to some empathy models, facial affect recognition constitutes only one component of empathic behavior, besides emotional perspective taking and affective responsiveness. It remains unclear whether menstrual cycle phase and thus estradiol and progesterone levels are also associated with the two other empathy constructs. Therefore, we investigated 40 healthy right-handed females, 20 during their follicular phase and 20 during their midluteal phase and compared their performance in three tasks tapping the empathic components as well as self-report data. Salivary hormone levels were obtained and correlated with performance parameters. Subjects were matched for age and education and did not differ in neuropsychological function. Analysis of empathy performance revealed a significant effect of phase in emotion recognition, showing higher accuracy in the follicular group. Regarding affective responsiveness, we observed a significant difference in reaction times, with faster responses for sad and angry stimuli in the midluteal group. No significant group difference emerged for emotional perspective taking. Furthermore, significant correlations between progesterone levels and emotion recognition accuracy and affective responsiveness emerged only in the luteal group. However, groups did not differ in self-reported empathy. Our results indicate that menstrual cycle phase and thus ovarian hormone concentration are differentially related to empathic behavior, particularly emotion recognition and responsiveness to negative situations, with progesterone covarying with both in the luteal phase.


Common Variants in Psychiatric Risk Genes Predict Brain Structure at Birth

Rebecca Knickmeyer et al.
Cerebral Cortex, forthcoming

Studies in adolescents and adults have demonstrated that polymorphisms in putative psychiatric risk genes are associated with differences in brain structure, but cannot address when in development these relationships arise. To determine if common genetic variants in disrupted-in-schizophrenia-1 (DISC1; rs821616 and rs6675281), catechol-O-methyltransferase (COMT; rs4680), neuregulin 1 (NRG1; rs35753505 and rs6994992), apolipoprotein E (APOE; ɛ3ɛ4 vs. ɛ3ɛ3), estrogen receptor alpha (ESR1; rs9340799 and rs2234693), brain-derived neurotrophic factor (BDNF; rs6265), and glutamate decarboxylase 1 (GAD1; rs2270335) are associated with individual differences in brain tissue volumes in neonates, we applied both automated region-of-interest volumetry and tensor-based morphometry to a sample of 272 neonates who had received high-resolution magnetic resonance imaging scans. ESR1 (rs9340799) predicted intracranial volume. Local variation in gray matter (GM) volume was significantly associated with polymorphisms in DISC1 (rs821616), COMT, NRG1, APOE, ESR1 (rs9340799), and BDNF. No associations were identified for DISC1 (rs6675281), ESR1 (rs2234693), or GAD1. Of note, neonates homozygous for the DISC1 (rs821616) serine allele exhibited numerous large clusters of reduced GM in the frontal lobes, and neonates homozygous for the COMT valine allele exhibited reduced GM in the temporal cortex and hippocampus, mirroring findings in adults. The results highlight the importance of prenatal brain development in mediating psychiatric risk.


Sensation seeking genes and physical activity in youth

Anna Wilkinson et al.
Genes, Brain and Behavior, forthcoming

Many studies examining genetic influences on physical activity (PA) have evaluated the impact of single nucleotide polymorphisms (SNPs) related to the development of lifestyle-related chronic diseases, under the hypothesis that they would be associated with PA. However, PA is a multi-determined behavior and associated with a multitude of health consequences. Thus, examining a broader range of candidate genes associated with a boarder range of PA correlates may provide new insights into the genetic underpinnings of PA. In this study we focus on one such correlate - sensation seeking behavior. Participants (N=1,130 Mexican origin youth) provided a saliva sample and data on PA and sensation seeking tendencies in 2008-09. Participants were genotyped for 630 functional and tagging variants in the dopamine, serotonin, and cannabinoid pathways. Overall 30% of participants (males - 37.6%; females - 22.0%) reported ≥60 minutes of PA on five out of seven days. After adjusting for gender, age and population stratification, and applying the Bayesian False Discovery Probability approach for assessing noteworthiness, four gene variants were significantly associated with PA. In a multivariable model, being male, having higher sensation seeking tendencies and at least one copy of the minor allele for SNPs in ACE (rs8066276 OR=1.44;p=0.012) and TPH2 (rs11615016 OR=1.73;p=0.021) were associated with increased likelihood of meeting PA recommendations. Participants with at least one copy of the minor allele for SNPs in SNAP25 (rs363035 OR=0.53;p=0.005) and CNR1 (rs6454672 OR=0.62;p=0.022) have decreased likelihood of meeting PA recommendations. Our findings extend current knowledge of the complex relationship between PA and possible genetic underpinnings.


Physical activity and obesity mediate the association between childhood motor function and adolescents' academic achievement

Marko Kantomaa et al.
Proceedings of the National Academy of Sciences, forthcoming

The global epidemic of obesity and physical inactivity may have detrimental implications for young people's cognitive function and academic achievement. This prospective study investigated whether childhood motor function predicts later academic achievement via physical activity, fitness, and obesity. The study sample included 8,061 children from the Northern Finland Birth Cohort 1986, which contains data about parent-reported motor function at age 8 y and self-reported physical activity, predicted cardiorespiratory fitness (cycle ergometer test), obesity (body weight and height), and academic achievement (grades) at age 16 y. Structural equation models with unstandardized (B) and standardized (β) coefficients were used to test whether, and to what extent, physical activity, cardiorespiratory fitness, and obesity at age 16 mediated the association between childhood motor function and adolescents' academic achievement. Physical activity was associated with a higher grade-point average, and obesity was associated with a lower grade-point average in adolescence. Furthermore, compromised motor function in childhood had a negative indirect effect on adolescents' academic achievement via physical inactivity (B = -0.023, 95% confidence interval = -0.031, -0.015) and obesity (B = -0.025, 95% confidence interval = -0.039, -0.011), but not via cardiorespiratory fitness. These results suggest that physical activity and obesity may mediate the association between childhood motor function and adolescents' academic achievement. Compromised motor function in childhood may represent an important factor driving the effects of obesity and physical inactivity on academic underachievement.


Does the level of physical exercise affect physiological and psychological responses to psychosocial stress in women?

Sandra Klaperski et al.
Psychology of Sport and Exercise, March 2013, Pages 266-274

Objectives: To test the Cross-Stressor Adaptation hypothesis for females by examining whether physically exercising young women show reduced physiological and psychological stress responses to a psychosocial stressor.

Design: Forty-seven healthy young women with different levels of physical exercise (17 not or rarely exercising, 15 moderately exercising, 15 vigorously exercising) underwent the Trier Social Stress Test for Groups (TSST-G); physiological and psychological stress responses during and after stress induction were compared.

Method: ANOVAs with repeated measures were used to compare stress reactivity and recovery between the three exercise groups. Heart rate and salivary free cortisol were used as indicators of physiological stress response, state anxiety, mood, and calmness as indicators of psychological stress response. For physiological stress reactivity, the areas under the curve with respect to the ground (AUCG) were compared.

Results: In all three exercise groups, experimentally induced stress led to a significant rise in heart rate, cortisol, and state anxiety; mood and calmness significantly decreased. As hypothesized, the pattern of the physiological stress response differed for the three exercise groups, with lowered reactivity in the more active groups. However, the psychological stress response partly went in the opposite direction: Exercising participants reported a higher mood decrease, suggesting a dissociation of the physiological and psychological stress responses.

Conclusions: The findings suggest that the Cross-Stressor Adaptation hypothesis is also valid for young women; however, only with regard to physiological stress response. The unexpected findings for psychological stress response need to be further explored in experimental studies.


Repetitive transcranial magnetic stimulation over the temporoparietal junction influences distinction of self from famous but not unfamiliar others

Christine Heinisch, Marie Krüger & Martin Brüne
Behavioral Neuroscience, December 2012, Pages 792-796

Neuroimaging and studies using repetitive transcranial magnetic stimulation (rTMS) have shown that a hierarchically organized neural network comprising the right temporoparietal junction (TPJ) and the prefrontal cortex is involved when discriminating one's own face from other faces. Less clear, however, is the role of attention in self-other distinction. Accordingly, the present study aimed at investigating the role of the right TPJ in self-other and other-other discrimination by using low-frequency repetitive TMS while controlling for attention. We tested 10 healthy right-handed subjects using a video task, which comprised morphings of famous, unfamiliar, and the subjects' own faces that gradually transformed into each other. Reaction time (RT) was measured by pushing a mouse button once a change of identity was recognized. Subjects received rTMS over the right TPJ, sham stimulation, or no stimulation, separated by 1 week. rTMS over the right TPJ influenced the distinction between one's own and a famous face. Specifically, subjects needed more features to identify the famous face after rTMS to the right TPJ compared with the control conditions. No rTMS effect was observed when subjects had to distinguish between their own and unfamiliar faces, nor did rTMS affect attention. This suggests that the right TPJ is involved in self-other distinction, specifically if the other's face is familiar to the subject.

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