Research review: the neurobiology and genetics of maltreatment and adversity

Review: Bridging research and practice: relational interventions for maltreated children

BACKGROUND: Research has consistently demonstrated the deleterious consequences of child maltreatment, not only during childhood but also across the life course. In particular, maltreatment negatively affects child attachment, with high percentages of maltreated children developing insecure or disorganized attachments with their primary caregiver. Therefore, interventions informed by attachment theory are important to prevent enduring relational difficulties. SCOPE: One such intervention, child-parent psychotherapy, has been shown to be efficacious in a number of randomized controlled trials. This article provides an overview of the evidence base for this intervention and the translation of this research into practice, particularly in community settings. CONCLUSION: Increasingly, it is imperative that such evidence-based models of intervention be translated into community settings so that the most vulnerable children and families can benefit from them.

Maternal deprivation induces deficits in temporal memory and cognitive flexibility and exaggerates synaptic plasticity in the rat medial prefrontal cortex

Early life adverse events can lead to structural and functional impairments in the prefrontal cortex (PFC). Here, we investigated whether maternal deprivation (MD) alters PFC-dependent executive functions, neurons and astrocytes number and synaptic plasticity in adult male Long-Evans rats. The deprivation protocol consisted of a daily separation of newborn Long-Evans pups from their mothers and littermates 3h/day postnatal day 1-14. Cognitive performances were assessed in adulthood using the temporal order memory task (TMT) and the attentional set-shifting task (ASST) that principally implicates the PFC and the Morris water maze task (WMT) that does not essentially rely on the PFC. The neurons and astrocytes of the prelimbic (PrL) area of the medial PFC (mPFC) were immunolabelled respectively with anti-NeuN and anti-GFAP antibodies and quantified by stereology. The field potentials evoked by electrical stimulation of ventral hippocampus (ventral HPC) were recorded in vivo in the PrL area. In adulthood, MD produced cognitive deficits in two PFC-dependent tasks, the TMT and ASST, but not in the WMT. In parallel, MD induced in the prelimbic area of the medial PFC an upregulation of long-term potentiation (LTP), without any change in the number of neurons and astrocytes. We provide evidence that MD leads in adults to an alteration of the cognitive abilities dependent on the PFC, and to an exaggerated synaptic plasticity in this region. We suggest that this latter phenomenon may contribute to the impairments in the cognitive tasks.

5-HTTLPR-environment interplay and its effects on neural reactivity in adolescents

It is not known how 5-HTTLPR genotype × childhood adversity (CA) interactions that are associated with an increased risk for affective disorders in population studies operate at the neural systems level. We hypothesized that healthy adolescents at increased genetic and environmental risk for developing mood disorders (depression and anxiety) would demonstrate increased amygdala reactivity to emotional stimuli compared to those with only one such risk factor or those with none. Participants (n = 67) were classified into one of 4 groups dependent on being homozygous for the long or short alleles within the serotonin-transporter-linked polymorphic region (5-HTTLPR) of the SLC6A4 gene and exposure to CA in the first 11 years of life (present or absent). A functional magnetic resonance imaging investigation was undertaken which involved viewing emotionally-salient face stimuli. In addition, we assessed the role of other variables hypothesized to influence amygdala reactivity, namely recent negative life-events (RNLE) assessed at ages 14 and 17, current anxiety symptoms and psychiatric history. We replicated prior findings demonstrating moderation by gene variants in 5-HTTLPR, but found no support for an effect of CA on amygdala reactivity. We also found a significant effect of RNLE aged 17 with amygdala reactivity demonstrating additive, but not interactive effects with 5-HTTLPR. A whole-brain analysis found a 5-HTTLPR × CA interaction in the lingual gyrus whereby CA appears to differentially modify neural reactivity depending on genotype. These results demonstrate that two different forms of environmental adversities interplay with 5-HTTLPR and thereby differentially impact amygdala and cortical reactivity.

The link between child abuse and psychopathology: a review of neurobiological and genetic research

Childhood abuse is associated with later psychopathology, including conduct disorder, antisocial personality disorder, anxiety and depression as well as a heightened risk of health and social problems. However, the neurobiological mechanisms by which childhood adversity increases vulnerability to psychopathology remain poorly understood. There is likely to be a complex interaction between environmental experiences (such as abuse) and individual differences in risk versus protective genes, which influences the neurobiological circuitry underpinning psychological and emotional development. Neuroendocrine studies indicate an association between early adversity and atypical development of the hypothalamic-pituitary-adrenal (HPA) axis stress response, which may predispose to psychiatric vulnerability in adulthood. Brain imaging research in children and adults is providing evidence of several structural and functional brain differences associated with early adversity. Structural differences have been reported in the corpus callosum, cerebellum and prefrontal cortex. Functional differences have been reported in regions implicated in emotional and behavioural regulation, including the amygdala and anterior cingulate cortex. These differences at the neurobiological level may represent adaptations to early experiences of heightened stress that lead to an increased risk of psychopathology. We also consider the clinical implications of future neurobiological and genetic research.

Do child abuse and maltreatment increase risk of schizophrenia?

INTRODUCTION

Although childhood abuse is a recognised risk factor for depression, post-traumatic stress disorder, and substance misuse, its role in the aetiology of psychotic disorder remained controversial. This is in part because the putative effect of childhood trauma on psychosis has been mostly evaluated by small, cross sectional, uncontrolled studies that raised methodological issues.

METHODS

Papers concerning the association between childhood trauma and psychotic disorders (to November, 2011) were identified using a comprehensive search of PubMed, Psychinfo, and Scopus and analysing reference list of relevant papers. A narrative synthesis was used to summarise results.

RESULTS

An association between childhood abuse and psychotic symptoms was consistently reported by large cross sectional surveys with an effect ranging from 1.7 to 15. However, we cannot conclude that the relationship is causal as lack of longitudinal studies prevent us from fully excluding alternative explanations such as reverse causality. Gender, cannabis use, and depressive and post-traumatic stress disorder symptoms appear to moderate the effect of childhood trauma on psychotic disorders. However, specificity of childhood abuse in psychotic disorders and, particularly, in schizophrenia has not been demonstrated.

CONCLUSION

Although the association between childhood abuse and psychosis has been replicated, the etiological role of such early adversity has yet to be fully clarified. So far none of the studies reported support the hypothesis that childhood abuse is either sufficient or necessary to develop a psychotic disorder. It seems likely that any effect of childhood abuse on schizophrenia needs to be understood in terms of genetic susceptibility and interaction with other environmental risk factors.

Parent emotional expressiveness and children's self-regulation: associations with abused children's school functioning

OBJECTIVE

Identifying factors associated with school functioning of abused children is important in prevention of long-term negative outcomes associated with school failure. The purpose of this study was to examine the degree to which parent emotional expressiveness and children's self-regulation predicted early school behavior of abused children.

METHODS

The sample included 92 physically abused children ages 4-7 and one of their parents (95.7% mothers). Parents completed a measure of their own emotional expressiveness, and parents and teachers provided reports of children's self-regulatory skills. Children's school functioning was measured by observations of playground aggression and teacher reports of aggression and classroom behavior.

RESULTS

Parents' expression of positive and negative emotions was associated with various aspects of children's self-regulation and functioning in the school setting. Links between self-regulation and children's school adjustment were robust; poor self-regulation was associated with higher aggression and lower cooperation and self-directed behavior in the classroom. There was minimal support for a mediating role of children's self-regulation in links between parent expressiveness and children's behavior.

PRACTICE IMPLICATIONS

Findings point to the relevance of parent emotional expressivity and children's self-regulatory processes in understanding physically abused children's functioning at the transition to school. Although further research is needed, findings indicate that increasing parental expression of positive emotion should be a focus in treatment along with reduction in negativity of abusive parents. Further, addressing children's self-regulation could be important in efforts to reduce aggression and enhance children's classroom competence.

Neuroimaging of child abuse: a critical review

Childhood maltreatment is a stressor that can lead to the development of behavior problems and affect brain structure and function. This review summarizes the current evidence for the effects of childhood maltreatment on behavior, cognition and the brain in adults and children. Neuropsychological studies suggest an association between child abuse and deficits in IQ, memory, working memory, attention, response inhibition and emotion discrimination. Structural neuroimaging studies provide evidence for deficits in brain volume, gray and white matter of several regions, most prominently the dorsolateral and ventromedial prefrontal cortex but also hippocampus, amygdala, and corpus callosum (CC). Diffusion tensor imaging (DTI) studies show evidence for deficits in structural interregional connectivity between these areas, suggesting neural network abnormalities. Functional imaging studies support this evidence by reporting atypical activation in the same brain regions during response inhibition, working memory, and emotion processing. There are, however, several limitations of the abuse research literature which are discussed, most prominently the lack of control for co-morbid psychiatric disorders, which make it difficult to disentangle which of the above effects are due to maltreatment, the associated psychiatric conditions or a combination or interaction between both. Overall, the better controlled studies that show a direct correlation between childhood abuse and brain measures suggest that the most prominent deficits associated with early childhood abuse are in the function and structure of lateral and ventromedial fronto-limbic brain areas and networks that mediate behavioral and affect control. Future, large scale multimodal neuroimaging studies in medication-naïve subjects, however, are needed that control for psychiatric co-morbidities in order to elucidate the structural and functional brain sequelae that are associated with early environmental adversity, independently of secondary co-morbid conditions.

Pathways to lifespan health following childhood parental death

The death of a parent is a profoundly stressful form of childhood adversity, increasing the short- and long-term risk of mental health problems. Emerging research suggests it may also disrupt biological regulatory systems and increase the risk of long-term physical health problems. This article presents a theoretical framework of the process by which the experience of parental death during childhood may influence mental and physical health outcomes over time. Drawing from a broad literature on adaptation following childhood parental loss, we focus on risk and protective factors in the childhood environment that are theoretically and empirically linked to emotional and biological regulatory responses to stress later in life, the effects of which may accumulate to impact long-term health.

Childhood adversity and immune and inflammatory biomarkers associated with cardiovascular risk in youth: a systematic review

BACKGROUND

Research suggests that adverse experiences in childhood affect the development of cardiovascular disease (CVD), and immune and inflammation dysregulation has been postulated to play role. However, it is unclear whether the effects of social adversity on immune-related biomarkers are evident in early life, and if these biomarkers may provide an early risk marker for targeting prevention and intervention. The purpose of this review is to evaluate research on the relationship between adversity and CVD-relevant immune biomarkers in youth, assess the consistency of the findings, and consider what additional research is needed.

METHODS

PubMed and PsycINFO searches were conducted through September 2011. Studies were selected using criteria related to the childhood exposure, biomarker outcome, age range, and sample selection. Twenty articles were identified, examining associations between childhood adversity and immune biomarkers (assessed during childhood) that are potential risk markers for CVD later in life.

RESULTS

Although childhood adversity was not consistently related to youth levels of inflammatory and other immune markers relevant to CVD, a trend toward positive findings was observed. No detectable patterns were evident based on measure of adversity, biomarker, study design, or sample size.

CONCLUSIONS

Overall, our findings suggest this avenue of research is worth continued investigation. We offer recommendations for future research related to (1) study design and sample, (2) definition and measurement of adversity, (3) statistical analysis, and (4) outcomes that will help distinguish whether there are immunologic alterations related to adversity and subsequent CVD risk that can be reliably detected in childhood.

The neurodevelopmental origins of suicidal behavior

Suicide and related behaviors are complex phenomena associated with different risk factors. Although most individuals who display suicidal behavior do not have a history of early-life adversity, a significant minority does. Recent animal and human data have suggested that early-life adversity leads to epigenetic regulation of genes involved in stress-response systems. Here, we review this evidence and suggest that early-life adversity increases risk of suicide in susceptible individuals by influencing the development of stable emotional, behavioral and cognitive phenotypes that are likely to result from the epigenetic regulation of the hypothalamic-pituitary-adrenal axis and other systems involved in responses to stress.

Normalizing the development of cortisol regulation in maltreated infants through preventive interventions

Longitudinal effects of child maltreatment on cortisol regulation in infants from age 1 to 3 years were investigated in the context of a randomized preventive intervention trial. Thirteen-month-old infants from maltreating families (N = 91) and their mothers were randomly assigned to one of three intervention conditions: child-parent psychotherapy, psychoeducational parenting intervention, and a control group involving standard community services (CS). A fourth group of infants from nonmaltreating families (N = 52) and their mothers comprised a nonmaltreated comparison (NC) group. The two active interventions were combined into one maltreated intervention (MI) group for statistical analyses. Saliva samples were obtained from children at 10:00 a.m. before beginning a laboratory observation session with their mothers when the children were 13 months of age (preintervention), 19 months (midintervention), 26 months (postintervention), and 38 months (1-year postintervention follow-up). At the initial assessment, no significant differences among groups in morning cortisol were observed. Latent growth curve analyses examined trajectories of cortisol regulation over time. Beginning at midintervention, divergence was found among the groups. Whereas the MI group remained indistinguishable from the NC group across time, the CS group progressively evinced lower levels of morning cortisol, statistically differing from the MI and NC groups. Results highlight the value of psychosocial interventions for early child maltreatment in normalizing biological regulatory processes.

Influence of early life stress on later hypothalamic-pituitary-adrenal axis functioning and its covariation with mental health symptoms: a study of the allostatic process from childhood into adolescence

The hypothalamic-pituitary-adrenal (HPA) axis is a primary mechanism in the allostatic process through which early life stress (ELS) contributes to disease. Studies of the influence of ELS on children's HPA axis functioning have yielded inconsistent findings. To address this issue, the present study considers multiple types of ELS (maternal depression, paternal depression, and family expressed anger), mental health symptoms, and two components of HPA functioning (traitlike and epoch-specific activity) in a long-term prospective community study of 357 children. ELS was assessed during the infancy and preschool periods; mental health symptoms and cortisol were assessed at child ages 9, 11, 13, and 15 years. A three-level hierarchical linear model addressed questions regarding the influences of ELS on HPA functioning and its covariation with mental health symptoms. ELS influenced traitlike cortisol level and slope, with both hyper- and hypoarousal evident depending on type of ELS. Further, type(s) of ELS influenced covariation of epoch-specific HPA functioning and mental health symptoms, with a tighter coupling of HPA alterations with symptom severity among children exposed previously to ELS. Results highlight the importance of examining multiple types of ELS and dynamic HPA functioning in order to capture the allostatic process unfolding across the transition into adolescence.

The linkages among childhood maltreatment, adolescent mental health, and self-compassion in child welfare adolescents

OBJECTIVES

Childhood maltreatment is a robust risk factor for poor physical and mental health. Child welfare youths represent a high-risk group, given the greater likelihood of severe or multiple types of maltreatment. This study examined the relationship between childhood maltreatment and self-compassion - a concept of positive acceptance of self. While not applied previously to a child welfare sample, self-compassion may be of value in understanding impairment among maltreatment victims. This may be most pertinent in adolescence and young adulthood, when self-identity is a focal developmental process.

METHODS

The present sample was drawn from the Maltreatment and Adolescent Pathways (MAP) Longitudinal Study, which followed randomly selected adolescents receiving child protection services across two years within an urban catchment area. Child maltreatment was assessed at baseline using the Childhood Trauma Questionnaire (Bernstein et al., 1994, 2003). Mental health, substance and alcohol use problems, suicide attempt, and self-compassion were assessed at the two-year follow-up point. There were 117 youths, aged 16-20 years (45.3% males) who completed the self-compassion scale (Neff, 2003). Bivariate correlations were computed between adolescent self-compassion and each form of self-reported maltreatment (physical abuse, sexual abuse, emotional abuse, emotional neglect, and physical neglect). Finally, hierarchical, stepwise regression was used to examine unique contributions of child maltreatment subtypes in predicting adolescent self-compassion, as well as maltreatment-related impairment.

RESULTS

Higher childhood emotional abuse, emotional neglect, and physical abuse were associated with lower self-compassion. Controlling for age and gender, emotional abuse was significantly associated with reduced self-compassion, even when the effects of emotional neglect and physical abuse were taken into account. Youths with low self-compassion were more likely to have psychological distress, problem alcohol use, and report a serious suicide attempt, as compared with those with high self-compassion. A number of maltreatment-related areas of impairment, identified by screening instruments, were significantly associated with lower self-compassion.

CONCLUSION

Self-compassion may be a fruitful aspect of research to pursue in an effort to better understand the impact of childhood emotional abuse on adolescent functioning, particularly considering the under-researched group of those receiving child protective services.

The impact of environmental experiences on symptoms of anxiety and depression across the life span

Symptoms of anxiety and depression are relatively stable over time. Can this stability be explained by genetic influences, or is it caused by the long-lasting effects of accumulating environmental experiences? To address this question, we analyzed longitudinally assessed symptoms of anxiety and depression in eight samples of monozygotic twins of widely varying ages. These samples were drawn from American and European population-based registries. Using hierarchical linear modeling, we examined individual differences and individual changes in the level of symptoms over time. This method enabled us to decompose the variance into the predictable variance shared by both members of each pair of twins, the differences between individuals within pairs, and the residual variance. We then modeled how these components of individual variation changed over time. Within pairs, the twins' predicted levels of symptoms increasingly diverged from childhood until late adulthood, at which point the divergence ceased. By middle adulthood, environmental experiences contributed substantially to stable and predictable interindividual differences in levels of anxiety and depression.

Interpersonal stress regulation and the development of anxiety disorders: an attachment-based developmental framework

Anxiety disorders represent a common but often debilitating form of psychopathology in both children and adults. While there is a growing understanding of the etiology and maintenance of these disorders across various research domains, only recently have integrative accounts been proposed. While classical attachment history has been a traditional core construct in psychological models of anxiety, contemporary attachment theory has the potential to integrate neurobiological and behavioral findings within a multidisciplinary developmental framework. The current paper proposes a modern attachment theory-based developmental model grounded in relevant literature from multiple disciplines including social neuroscience, genetics, neuroendocrinology, and the study of family factors involved in the development of anxiety disorders. Recent accounts of stress regulation have highlighted the interplay between stress, anxiety, and activation of the attachment system. This interplay directly affects the development of social-cognitive and mentalizing capacities that are acquired in the interpersonal context of early attachment relationships. Early attachment experiences are conceptualized as the key organizer of a complex interplay between genetic, environmental, and epigenetic contributions to the development of anxiety disorders - a multifactorial etiology resulting from dysfunctional co-regulation of fear and stress states. These risk-conferring processes are characterized by hyperactivation strategies in the face of anxiety. The cumulative allostatic load and subsequent "wear and tear" effects associated with hyperactivation strategies converge on the neural pathways of anxiety and stress. Attachment experiences further influence the development of anxiety as potential moderators of risk factors, differentially impacting on genetic vulnerability and relevant neurobiological pathways. Implications for further research and potential treatments are outlined.

Childhood maltreatment in subjects with male-to-female gender identity disorder

Childhood maltreatment (CM) is quite common and constitutes a nonspecific risk factor for a range of different psychiatric symptoms during lifespan. It has been demonstrated that sexual minorities are at higher risk of maltreatment and abuse, and a high proportion of transsexual subjects report CM. The aim of this study is to evaluate the prevalence of reported CM in a clinical sample of patients with male-to-female Gender Identity Disorder (MtF GID), and to explore the relationship between these early life events, body image and different psychopathological and clinical variables. A consecutive series of 162 patients with male genotype was evaluated from July 2008 to May 2010. A total of 109 subjects (mean age 36 ± 10 years) meeting the criteria for MtF GID and giving their informed consent were considered. The occurrence of CM experiences was evaluated through a face-to-face clinical interview. Patients were asked to complete the Body Uneasiness Test and Symptom Checklist-90 Revised. More than one-fourth of patients reported CM. Maltreated subjects reported a higher body dissatisfaction and display a worse lifetime mental health. The presence of reported CM in these patients has relevant psychopathological implications, and therefore should be carefully investigated.

Understanding and promoting resilience in children and youth

PURPOSE OF REVIEW

In a context of global concern about the consequences of stress and extreme adversities, advances in theory and methods for studying human resilience have ushered in a new era of integrative, biopsychosocial research. This review highlights recent theory, findings, and implications of resilience research on young people.

RECENT FINDINGS

Resilience research has shifted toward dynamic system models with multiple levels of interaction, including research on the neurobiology of stress and adaption, epigenetic processes, and disasters. Growing evidence indicates individual differences in biological sensitivity to negative and positive experiences, including interventions. Early experiences show enduring programming effects on key adaptive systems, underscoring the importance of early intervention. Studies of developmental cascades demonstrate spreading effects of competence and symptoms over time, with important implications for the timing and targeting of interventions. Disaster research suggests guidelines for planning to protect children in the event of large-scale trauma.

SUMMARY

Research is integrating the study of resilience across system levels, with implications for promoting positive adaptation of young people faced with extreme adversity. However, studies on neurobiological and epigenetic processes are just beginning, and more research is needed on efficacy, as well as strategic timing and targeting, of interventions.

Cumulative Effects of Prenatal Substance Exposure and Early Adversity on Foster Children's HPA Axis Reactivity During a Psychosocial Stressor

Dysregulated hypothalamic-pituitary-adrenocortical (HPA) axis stress response has been reported among individuals with prenatal substance exposure and those with early adversity. However, few researchers have examined the combined effects of these risk factors. Patterns of HPA reactivity among maltreated foster children with and without prenatal substance exposure (N = 53; ages 9-12 years) were examined using the Trier Social Stress Test for Children. Area under the curve with respect to increase (AUC(I)) analyses revealed that prenatal substance exposure or physical abuse significantly increased the likelihood of a negative AUC(I) (i.e., little or no HPA reactivity). Among children with prenatal substance exposure and physical abuse, 85% exhibited a negative AUC(I). The results underscore the importance of addressing this combined risk.

Early-life stress and cognitive outcome

RATIONALE

Early-life stress is associated with later neuropsychiatric illness. While the association between early-life stress and brain development is well recognized, relatively few studies have examined the association between exposure to early-life stress and cognitive outcome.

OBJECTIVES

The objective of this paper is to examine the association between early-life stress and cognitive outcome in animal models and humans.

METHODS

In this article, we review alterations in cognitive function associated with early-life stress in animals and then discuss the association of early-life stress and cognitive function in humans.

RESULTS

Findings suggest that early-life stress is associated with abnormal cognitive function in animals and humans. Furthermore, cognitive deficits associated with exposure to early-life stress in humans may persist into at least early adulthood, although animal models of enriched environments and studies of children adopted from institutionalized care into foster families suggest that certain social factors may at least partially reverse cognitive deficits following exposure to early-life stress.

CONCLUSIONS

Exposure to stress in early life may be associated with later deficits in cognitive function.

Epigenetics of early child development

Comprehensive clinical studies show that adverse conditions in early life can severely impact the developing brain and increase vulnerability to mood disorders later in life. During early postnatal life the brain exhibits high plasticity which allows environmental signals to alter the trajectories of rapidly developing circuits. Adversity in early life is able to shape the experience-dependent maturation of stress-regulating pathways underlying emotional functions and endocrine responses to stress, such as the hypothalamo-pituitary-adrenal (HPA) system, leading to long-lasting altered stress responsivity during adulthood. To date, the study of gene-environment interactions in the human population has been dominated by epidemiology. However, recent research in the neuroscience field is now advancing clinical studies by addressing specifically the mechanisms by which gene-environment interactions can predispose individuals toward psychopathology. To this end, appropriate animal models are being developed in which early environmental factors can be manipulated in a controlled manner. Here we will review recent studies performed with the common aim of understanding the effects of the early environment in shaping brain development and discuss the newly developing role of epigenetic mechanisms in translating early life conditions into long-lasting changes in gene expression underpinning brain functions. Particularly, we argue that epigenetic mechanisms can mediate the gene-environment dialog in early life and give rise to persistent epigenetic programming of adult physiology and dysfunction eventually resulting in disease. Understanding how early life experiences can give rise to lasting epigenetic marks conferring increased risk for mental disorders, how they are maintained and how they could be reversed, is increasingly becoming a focus of modern psychiatry and should pave new guidelines for timely therapeutic interventions.

The impact of childhood maltreatment: a review of neurobiological and genetic factors

Childhood maltreatment represents a significant risk factor for psychopathology. Recent research has begun to examine both the functional and structural neurobiological correlates of adverse care-giving experiences, including maltreatment, and how these might impact on a child's psychological and emotional development. The relationship between such experiences and risk for psychopathology has been shown to vary as a function of genetic factors. In this review we begin by providing a brief overview of neuroendocrine findings, which indicate an association between maltreatment and atypical development of the hypothalamic-pituitary-adrenal axis stress response, which may predispose to psychiatric vulnerability in adulthood. We then selectively review the magnetic resonance imaging (MRI) studies that have investigated possible structural and functional brain differences in children and adults who have experienced childhood maltreatment. Differences in the corpus callosum identified by structural MRI have now been reliably reported in children who have experienced abuse, while differences in the hippocampus have been reported in adults with childhood histories of maltreatment. In addition, there is preliminary evidence from functional MRI studies of adults who have experienced childhood maltreatment of amygdala hyperactivity and atypical activation of frontal regions. These functional differences can be partly understood in the context of the information biases observed in event-related potential and behavioral studies of physically abused children. Finally we consider research that has indicated that the effect of environmental adversity may be moderated by genotype, reviewing pertinent studies pointing to gene by environment interactions. We conclude by exploring the extent to which the growing evidence base in relation to neurobiological and genetic research may be relevant to clinical practice and intervention.

Neuroendocrine aspects of pediatric aggression: Can hormone measures be clinically useful?

Pediatric aggression is common in human societies, mainly presenting as impulsive aggression or predatory aggression. Numerous psychiatric disorders can contain aggression as a symptom, leading to difficulties in diagnosis and treatment. This review focuses on the biological systems that affect pediatric aggression. We review the hypothalamic-pituitary-adrenal (HPA) axis, the hypothalamic-pituitary-gonadal (HPG) axis, and the mechanisms by which these axes influence the body and mind of aggressive children and adolescents. Although this review focuses on the HPA and HPG axes, it is important to note that other biological systems have relationships with these two axes. Based on the results of the studies reviewed, elevated cortisol concentrations were associated with impulsive aggression, whereas, low levels of cortisol were associated with callous-unemotional traits similar to predatory aggression. Higher levels of dehydroepiandrosterone were correlated with higher levels of aggression as were higher levels of testosterone. However, there have been discrepancies in the results between various studies, indicating the need for more research on hormonal levels and pediatric aggression. In the future, hormonal levels may be useful in determining what treatments will work best for certain pediatric patients.