Alterations in neural processing and psychopathology in children raised in institutions

Stress as a mediator of brain alterations in attention-deficit hyperactivity disorder: A systematic review

OBJECTIVE

Stress is a known risk factor for numerous psychopathologies, whereas evidence is lacking regarding the specific consequences of stress on the neural basis of attention-deficit hyperactivity disorder (ADHD). A systematic literature review was thus conducted to clarify the role of stress in the association between the resulting alterations of brain structure, connectivity, and function in ADHD.

METHODS

The study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) under identifier CRD42023379809. A systematic search of the PubMed and CINAHL databases was conducted for articles published prior to December 22nd, 2022. Retrieved literature was screened in Rayyan and data extraction was performed with respect to neuroimaging, stress exposure, and ADHD outcomes. The Quality in Prognosis Studies (QUIPS) tool was adapted based on the Conducting Systematic Reviews and Meta-Analyses of Observational Studies of Etiology (COSMOS-E) guidance article to assess risk of bias and quality of studies. Strength of the evidence was assessed under the guidance of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

RESULTS

Screening 25,026 non-duplicate articles yielded 20 eligible studies for inclusion. Exposure to early life trauma, institutionalization, prenatal smoking or alcohol consumption, air pollution, low socioeconomic status, or low birth weight were associated with alterations in brain structure, function, and connectivity in ADHD. However, most studies did not provide strong evidence due to small sample sizes and lack of statistical approaches to determine a direct mediation of the association between stress and ADHD by neural outcomes.

CONCLUSION

This systematic review was the first to summarize evidence of structural and functional stress-associated alterations in the brain, which were found to be directly and indirectly associated with ADHD outcomes. Overall, stress requires consideration as a significant determinant of neurodevelopmental outcomes in ADHD. However, extensive further research is warranted due to little available evidence and the difficulty of obtaining clear results. In light of such a complex research question, in order to confirm findings, provide further evidence, and establish causality systematic longitudinal studies would be required. Investigating the topic may provide invaluable information when it comes to tailoring prevention and treatment strategies in ADHD, and should be pursued in order to integrate the factor of stress into a more comprehensive understanding of ADHD.

Neural correlates of face familiarity in institutionalised children and links to attachment disordered behaviour

BACKGROUND

One of the most well-documented sequelae of early maltreatment and institutionalisation is attachment problems, including behaviours under the labels of reactive attachment disorder (RAD) and disinhibited social engagement disorder (DSED). Despite growing evidence of the neurobiological effects of institutionalisation, the neural correlates of these behavioural patterns are largely unknown.

METHODS

The current study examined effects of both institutionalisation in general and attachment disordered behaviour, in particular, on brain-based markers of face processing, in 100 Portuguese children (70 currently institutionalised, 30 continuously raised by their families). Children's neural processing of caregiver's and stranger's faces was assessed with Event-Related Potentials (ERPs).

RESULTS

Compared to children from the community, institutionalised children showed smaller amplitudes in the N170, to both stranger and caregiver faces. Amongst the institutionalised group, living in a setting with a higher children-to-caregivers' ratio was associated with smaller P400 amplitudes. The display of DSED symptoms was associated with a smaller P1 to both faces, as well as a reduced differentiation between faces in P400 amplitudes and smaller P400 to the stranger's face. In contrast, RAD symptoms were not associated with any ERP measures.

CONCLUSIONS

Results replicate previously reported hypoactivation in institutionalised children, in a less-globally deprived setting than past work, indicating that such a pattern is associated with lack of individualised care and increased symptoms of DSED.

Perinatal and early childhood biomarkers of psychosocial stress and adverse experiences

The human brain develops through a complex interplay of genetic and environmental influences. During critical periods of development, experiences shape brain architecture, often with long-lasting effects. If experiences are adverse, the effects may include the risk of mental and physical disease, whereas positive environments may increase the likelihood of healthy outcomes. Understanding how psychosocial stress and adverse experiences are embedded in biological systems and how we can identify markers of risk may lead to discovering new approaches to improve patient care and outcomes. Biomarkers can be used to identify specific intervention targets and at-risk children early when physiological system malleability increases the likelihood of intervention success. However, identifying reliable biomarkers has been challenging, particularly in the perinatal period and the first years of life, including in preterm infants. This review explores the landscape of psychosocial stress and adverse experience biomarkers. We highlight potential benefits and challenges of identifying risk clinically and different sub-signatures of stress, and in their ability to inform targeted interventions. Finally, we propose that the combination of preterm birth and adversity amplifies the risk for abnormal development and calls for a focus on this group of infants within the field of psychosocial stress and adverse experience biomarkers. IMPACT: Reviews the landscape of biomarkers of psychosocial stress and adverse experiences in the perinatal period and early childhood and highlights the potential benefits and challenges of their clinical utility in identifying risk status in children, and in developing targeted interventions. Explores associations between psychosocial stress and adverse experiences in childhood with prematurity and identifies potential areas of assessment and intervention to improve outcomes in this at-risk group.

Systematic Review and Meta-analysis: The Science of Early-Life Precursors and Interventions for Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

To evaluate which early neurocognitive and behavioral precursors are associated with the development of attention-deficit/hyperactivity disorder (ADHD) and whether these are currently targeted in early interventions.

METHOD

We conducted 2 systematic reviews and meta-analyses of empirical studies to examine the following: (1) early-life (0-5 years) neurocognitive and behavioral precursors associated with familial likelihood for ADHD, an early ADHD diagnosis/elevated ADHD symptoms, and/or the presence of later-childhood ADHD; and (2) interventions delivered to children aged 0 to 5 years targeting the identified precursors or measuring these as outcomes. Standardized mean differences (Hedges' g) and pre-post-treatment change scores (SMD) were computed.

RESULTS

A total of 149 studies (165,095 participants) investigating 8 neurocognitive and behavioral domains met inclusion criteria for part 1. Multi-level random-effects meta-analyses on 136 studies revealed significant associations between ADHD and poorer cognitive (g = -0.46 [95% CIs: -0.59, -0.33]), motor (g = -0.35 [CIs: -0.48, -0.21]) and language (g = -0.43 [CIs: -0.66, -0.19]) development, social (g = 0.23 [CIs: 0.03, 0.43]) and emotional (g = 0.46 [CIs: 0.33, 0.58]) difficulties, early regulatory (g = 0.30 [CIs: 0.18, 0.43]) and sleep (g = 0.29 [CIs: 0.14, 0.44]) problems, sensory atypicalities (g = 0.52 [CIs: 0.16, 0.88]), elevated activity levels (g = 0.54 [CIs: 0.37, 0.72]), and executive function difficulties (g = 0.34 [CIs: 0.05, 0.64] to -0.87 [CIs: -1.35, -0.40]). A total of 32 trials (28 randomized, 4 nonrandomized, 3,848 participants) testing early interventions that targeted the identified precursors met inclusion criteria for part 2. Multi-level random-effects meta-analyses on 22 studies revealed significant intervention-related improvements in ADHD symptoms (SMD = 0.43 [CIs: 0.22, 0.64]) and working memory (SMD = 0.37 [CIs: 0.06, 0.69]).

CONCLUSION

Children aged 0 to 5 years with current or later-emerging ADHD are likely to experience difficulties in multiple neurocognitive/behavioral functions. Early interventions show some effectiveness in reducing ADHD symptoms, but their effects on neurocognitive/behavioral difficulties require further study.

Cognitive Stimulation as a Mechanism Linking Socioeconomic Status With Executive Function: A Longitudinal Investigation

Executive functions (EF), including working memory, inhibition, and cognitive flexibility, vary as a function of socioeconomic status (SES), with children from economically disadvantaged backgrounds having poorer performance than their higher SES peers. Using observational methods, we investigated cognitive stimulation in the home as a mechanism linking SES with EF. In a sample of 101 children aged 60-75 months, cognitive stimulation fully mediated SES-related differences in EF. Critically, cognitive stimulation was positively associated with the development of inhibition and cognitive flexibility across an 18-month follow-up period. Furthermore, EF at T1 explained SES-related differences in academic achievement at T2. Early cognitive stimulation-a modifiable factor-may be a desirable target for interventions designed to ameliorate SES-related differences in cognitive development and academic achievement.

Living in a Disadvantaged Neighborhood Affects Neural Processing of Facial Trustworthiness

Neighborhood disorder (i.e., physical or social decay) is associated with decreased trust, which reinforces criminal behavior among some individuals in these communities. However, past research largely is descriptive and has not measured processes underlying trust. Using behavioral and neural indices [the late positive potential (LPP), a marker of salience elaboration] in a sample of adults (N = 55), we examined the association between perceived neighborhood disorder and facial trustworthiness perception as well as the potential moderating role of trustworthiness perception on the association between PND and criminal behavior. Individuals with higher perceived neighborhood disorder displayed less LPP differentiation between untrustworthy and trustworthy faces. Moreover, individuals with higher perceived neighborhood disorder and less LPP differentiation were less likely to commit a variety of crimes, whereas those with higher perceptions of neighborhood disorder and high LPP differentiation were more likely to commit a variety of crimes. Combined, these findings suggest that similarly processing trustworthy and untrustworthy faces, as indexed by less LPP differentiation, may reflect an adaptation among those with higher perceived neighborhood disorder that mitigates against deviant behavior and contacts with the law. Understanding the intersection between neighborhood characteristics and individual-level cognitive-affective processing may provide insight into what shapes beliefs and behaviors about important social information.

Distinct aspects of the early environment contribute to associative memory, cued attention, and memory-guided attention: Implications for academic achievement

Childhood socioeconomic status (SES) is associated with numerous aspects of cognitive development and disparities in academic achievement. The specific environmental factors that contribute to these disparities remain poorly understood. We used observational methods to characterize three aspects of the early environment that may contribute to SES-related differences in cognitive development: violence exposure, cognitive stimulation, and quality of the physical environment. We evaluated the associations of these environmental characteristics with associative memory, cued attention, and memory-guided attention in a sample of 101 children aged 60-75 months. We further investigated whether these specific cognitive abilities mediated the association between SES and academic achievement 18 months later. Violence exposure was specifically associated with poor associative memory, but not cued attention or memory-guided attention. Cognitive stimulation and higher quality physical environment were positively associated with cued attention accuracy, but not after adjusting for all other environmental variables. The quality of the physical environment was associated with memory-guided attention accuracy. Of the cognitive abilities examined, only memory-guided attention contributed to SES-related differences in academic achievement. These findings suggest specificity in how particular aspects of early environmental experience scaffold different types of attention and memory subserved by distinct neural circuits and shed light on a novel cognitive-developmental mechanism underlying SES-related disparities in academic achievement.

The role of the visual association cortex in scaffolding prefrontal cortex development: A novel mechanism linking socioeconomic status and executive function

Socioeconomic status (SES) is associated with executive function (EF) and prefrontal cortex (PFC) development. However, understanding of the specific aspects of SES that influence development of EF and the PFC remains limited. We briefly review existing literature on proposed mechanisms linking SES with EF. Then, we present a novel conceptual model arguing that early cognitive stimulation shapes EF and PFC development. We propose that cognitive stimulation drives lower-level sensory and perceptual processes that may impact EF and PFC development through reciprocal connections between the ventral visual stream and PFC. We argue that caregivers guide attention and associative learning, which provides children the opportunity to regulate attention and gain semantic knowledge. This experience in turn allows for opportunities to train the PFC to resolve conflict between stimuli with overlapping features and engage in increasingly complex computations as visual processing systems develop; this may lay the groundwork for development of EF. We review existing evidence for this model and end by highlighting how this conceptual model could launch future research questions.

Effects of methylphenidate on the ERP amplitude in youth with ADHD: A double-blind placebo-controlled cross-over EEG study

Methylphenidate (MPH) is a first line drug for attention-deficit/hyperactivity disorder (ADHD), yet the neuronal mechanisms underlying the condition and the treatment are still not fully understood. Previous EEG studies on the effect of MPH in ADHD found changes in evoked response potential (ERP) components that were inconsistent between studies. These inconsistencies highlight the need for a well-designed study which includes multiple baseline sessions and controls for possible fatigue, learning effects and between-days variability. To this end, we employ a double-blind placebo-controlled cross-over study and explore the effect of MPH on the ERP response of subjects with ADHD during a Go/No-Go cognitive task. Our ERP analysis revealed significant differences in ADHD subjects between the placebo and MPH conditions in the frontal-parietal region at 250ms-400ms post stimulus (P3). Additionally, a decrease in the late 650ms-800ms ERP component (LC) is observed in frontal electrodes of ADHD subjects compared to controls. The standard deviation of response time of ADHD subjects was significantly smaller in the MPH condition compared to placebo and correlated with the increased P3 ERP response in the frontoparietal electrodes. We suggest that mental fatigue plays a role in the decrease of the P3 response in the placebo condition compared to pre-placebo, a phenomenon that is significant in ADHD subjects but not in controls, and which is interestingly rectified by MPH.

Early Sexual Trauma Exposure and Neural Response Inhibition in Adolescence and Young Adults: Trajectories of Frontal Theta Oscillations During a Go/No-Go Task

OBJECTIVE

Trauma, particularly when experienced early in life, can alter neurophysiologic and behavioral development, thereby increasing risk for substance use disorders and related psychopathology. However, few studies have empirically examined trauma using well-characterized developmental samples that are followed longitudinally.

METHOD

The association of assaultive, non-assaultive, and sexual assaultive experiences before 10 years of age with developmental trajectories of brain function during response inhibition was examined by measuring electrophysiologic theta and delta oscillations during no-go and go conditions in an equal probability go/no-go task. Data were drawn from the Collaborative Study of the Genetics of Alcoholism (COGA) prospective cohort, composed of offspring who were aged 12 through 22 years at enrollment from high-risk and comparison families, with follow-ups at 2-year intervals since 2004. In addition, other important predictors of neurophysiologic functioning (eg, substance use, impulsivity, and parental alcohol use disorders) were investigated. Moreover, associations of neurophysiologic functioning with alcohol and cannabis use disorder symptom counts and externalizing and internalizing psychopathology were examined.

RESULTS

Individuals exposed to sexual assaultive trauma before 10 years of age had slower rates of change in developmental trajectories of no-go frontal theta during response inhibition. Importantly, effects remained significant after accounting for exposure to other traumatic exposures, such as parental history of alcohol use disorder and participants' substance use, but not measures of impulsivity. Further, slower rates of change in no-go frontal theta adolescent and young adult development were associated with increased risk for alcohol use disorder symptoms and internalizing psychopathology, but not for cannabis use disorder symptoms or externalizing psychopathology.

CONCLUSION

Childhood sexual assault is associated with atypical frontal neurophysiologic development during response inhibition. This could reflect alterations in frontal lobe development, synaptic pruning, and/or cortical maturation involving neural circuits for inhibitory control. These same areas could be associated with increased risk for young adult alcohol use disorder symptoms and internalizing psychopathology. These findings support the hypothesis that changes in neurocognitive development related to early sexual trauma exposure could increase the risk for mental health and substance use problems in young adulthood.

Adolescents with Persistent History of Maltreatment Fail in Antisaccadic Task

The antisaccadic task is sensitive to what is called frontal dysfunction, i.e. dysfunction of the frontal lobes of the cerebral cortex which are the basis for a wide range of symptoms. The present study examined saccadic eye movements in adolescents with persistent history of maltreatment. Participants included 17 female subjects with maltreatment history. The control group consisted of 54 typically developing female subjects. All participants were administered Child Behavior Checklist (CBCL) and saccadic eye movement tests. CBCL showed significant differences between the maltreated and control groups. The prosaccadic test revealed insignificant results between both groups. The antisaccadic test revealed a highly significant difference (longer latencies, more prosaccadic mistakes in the group of maltreated subjects). Antisaccadic eye movements may be regarded as a possible indicator of persistent maltreatment and following emotional and behavioral problems and may therefore enhance diagnostic methods.

Prenatal maternal mood patterns predict child temperament and adolescent mental health

BACKGROUND

This study quantifies the dynamics of maternal mood focusing on unpredictability, and to assess if greater unpredictability of prenatal maternal mood predicts child temperament and internalizing symptoms through early adolescence.

METHODS

The association between prenatal mood predictability and child internalizing symptoms were assessed in two longitudinal cohorts (N's = 227 and 180). Maternal mood was assessed repeatedly during pregnancy as early as 15 weeks' gestation. Predictability of maternal mood was calculated by applying Shannon's entropy to the distribution of responses on mood questionnaires. Maternal reports of child negative affectivity (a predictor of later internalizing) were collected at 6, 12, 24 months and 7 years of age. Child self-reports of anxiety symptoms were collected at 10 years and reports of depression symptoms at 13 years.

RESULTS

Fetal exposure to more elevated maternal mood entropy predicted higher levels of child negative affectivity at 12 months (r = .36; p < 01), 24 months (r = .31; p < 01) and 7 years (r = .32; p < 01) of age. In addition, children exposed to higher prenatal maternal mood entropy, reported higher levels of anxiety symptoms at 10 years (r = .24; p < 01) and elevated depressive symptoms at 13 years (r = .29; p < .01). These associations persisted after adjusting for maternal pre and postnatal mood valence (e.g. depression levels) and for other relevant demographic characteristics.

CONCLUSIONS

Our findings provide strong support for the notion that patterns of maternal mood influence the developing brain. More specifically, they suggest that prenatal maternal mood predictability may be a critical predictor of developmental mental health trajectories and should be considered when assessing early life influences on lifespan mental health.

Child violence experiences in institutionalised/orphanage care

Institutions are not necessarily good environments for children. In the face of challenges such as HIV, Ebola, poverty, conflict and disaster the numbers have grown rather than reduced. Some countries have closed institutions down -driven by findings that cognitive developmental delay is associated with institutional care. Yet insight into abuse and violence within institutionalised settings is neglected. Maltreatment -violence and abuse -may be an issue. This systematic review series addresses violence and abuse experiences in institutionalised care, exploring firstly the frequency of abuse/violence in institutions, secondly any interventions to reduce such violence or abuse and thirdly the perpetrators of such violence or abuse. The final systematic review updates the findings on cognitive delay associated with institutionalised care. With a violence lens, cognitive delay may well be considered under the umbrella of neglect. Maltreatment and abuse may be a driver of cognitive delay. The keyword search covered several electronic databases and studies were included for data abstraction if they met adequacy criteria. Eight studies were identified on the prevalence of abuse in institutions and a further three studies reported on interventions. Only one study was identified documenting peer on peer violence in institutions. Sixty-six studies were identified examining cognitive development for institutionalised children. All but two of these record cognitive deficits associated with institutionalisation. Only two asked about violence or abuse which was found to be higher in institutionalised children. Overall the abuse experiences of children in institutions are poorly recorded, and in one study violence was associated with high suicidal attempts. The major intervention pathway for ameliorating cognitive challenge seems to be placement out of the institutions which shows benefits and redresses some cognitive outcomes - yet not a total panacea. The single study providing training and monitoring of harsh punishment and maltreatment showed immediate and decided reductions. This data suggest, despite the paucity of studies, violence and abuse, by commission or omission is prevalent in institutions, has an effect on child well-being and is amenable to intervention. Simple training or more complex structures to place children within conducive alternative environments (or to avoid institutionalised placements in the first place) seem to be the main pathway of intervention.

Early experience and brain development

Healthy brain development takes place within the context of individual experience. Here, we describe how certain early experiences are necessary for typical brain development. We present evidence from multiple studies showing that severe early life neglect leads to alterations in brain development, which compromises emotional, behavioral, and cognitive functioning. We also show how early intervention can reverse some of the deleterious effects of neglect on brain development. We conclude by emphasizing that early interventions that start at the earliest possible point in human development are most likely to support maximal recovery from early adverse experiences. WIREs Cogn Sci 2017, 8:e1387. doi: 10.1002/wcs.1387 For further resources related to this article, please visit the WIREs website.

Reduced Working Memory Mediates the Link between Early Institutional Rearing and Symptoms of ADHD at 12 Years

Children who are raised in institutions show severe delays across multiple domains of development and high levels of psychopathology, including attention deficit/hyperactivity disorder (ADHD). Low performance in executive functions (EFs) are also common in institutionally reared children and often do not remediate following improvements in the caregiving environment. ADHD symptomatology also remains elevated even after children are removed from institutional care and placed in families. We investigate whether poor EF is a mechanism explaining elevated rates of ADHD in children reared in institutional settings in the Bucharest Early Intervention Project (BEIP). In the current study, we examine the potentially mediating role of poor EF in the association between institutionalization and symptoms of ADHD at age 12 years. A total of 107 children were assessed with the Cambridge Neuropsychological Test Automated Battery (CANTAB) on working memory, set-shifting and planning. We also obtained concurrent teacher reports on their levels of ADHD symptoms (inattention and impulsivity separately). Institutionalization strongly predicted elevations in symptoms of inattention and impulsivity at age 12 years (ps < 0.01). Indices of working memory and planning were also associated with ADHD after controlling for potential confounders (ps < 0.03). Mediation analyses revealed that poor working memory performance mediated the link between exposure to early institutionalization and higher scores of both inattention and impulsivity. These results replicate and extend the findings that we reported in the BEIP sample at age 8 years. Together, they suggest that compromised working memory is a key mechanism that continues to explain the strikingly high levels of ADHD in late childhood among children institutionalized in early life. Interventions targeting working memory may help to prevent ADHD among children exposed to institutional care.

Discrimination of amygdala response predicts future separation anxiety in youth with early deprivation

BACKGROUND

Significant disruption in caregiving is associated with increased internalizing symptoms, most notably heightened separation anxiety symptoms during childhood. It is also associated with altered functional development of the amygdala, a neurobiological correlate of anxious behavior. However, much less is known about how functional alterations of amygdala predict individual differences in anxiety. Here, we probed amygdala function following institutional caregiving using very subtle social-affective stimuli (trustworthy and untrustworthy faces), which typically result in large differences in amygdala signal, and change in separation anxiety behaviors over a 2-year period. We hypothesized that the degree of differentiation of amygdala signal to trustworthy versus untrustworthy face stimuli would predict separation anxiety symptoms.

METHODS

Seventy-four youths mean (SD) age = 9.7 years (2.64) with and without previous institutional care, who were all living in families at the time of testing, participated in an fMRI task designed to examine differential amygdala response to trustworthy versus untrustworthy faces. Parents reported on their children's separation anxiety symptoms at the time of scan and again 2 years later.

RESULTS

Previous institutional care was associated with diminished amygdala signal differences and behavioral differences to the contrast of untrustworthy and trustworthy faces. Diminished differentiation of these stimuli types predicted more severe separation anxiety symptoms 2 years later. Older age at adoption was associated with diminished differentiation of amygdala responses.

CONCLUSIONS

A history of institutional care is associated with reduced differential amygdala responses to social-affective cues of trustworthiness that are typically exhibited by comparison samples. Individual differences in the degree of amygdala differential responding to these cues predict the severity of separation anxiety symptoms over a 2-year period. These findings provide a biological mechanism to explain the associations between early caregiving adversity and individual differences in internalizing symptomology during development, thereby contributing to individualized predictions of future clinical outcomes.

Future Directions in Childhood Adversity and Youth Psychopathology

Despite long-standing interest in the influence of adverse early experiences on mental health, systematic scientific inquiry into childhood adversity and developmental outcomes has emerged only recently. Existing research has amply demonstrated that exposure to childhood adversity is associated with elevated risk for multiple forms of youth psychopathology. In contrast, knowledge of developmental mechanisms linking childhood adversity to the onset of psychopathology-and whether those mechanisms are general or specific to particular kinds of adversity-remains cursory. Greater understanding of these pathways and identification of protective factors that buffer children from developmental disruptions following exposure to adversity is essential to guide the development of interventions to prevent the onset of psychopathology following adverse childhood experiences. This article provides recommendations for future research in this area. In particular, use of a consistent definition of childhood adversity, integration of studies of typical development with those focused on childhood adversity, and identification of distinct dimensions of environmental experience that differentially influence development are required to uncover mechanisms that explain how childhood adversity is associated with numerous psychopathology outcomes (i.e., multifinality) and identify moderators that shape divergent trajectories following adverse childhood experiences. A transdiagnostic model that highlights disruptions in emotional processing and poor executive functioning as key mechanisms linking childhood adversity with multiple forms of psychopathology is presented as a starting point in this endeavour. Distinguishing between general and specific mechanisms linking childhood adversity with psychopathology is needed to generate empirically informed interventions to prevent the long-term consequences of adverse early environments on children's development.

Disruptions of working memory and inhibition mediate the association between exposure to institutionalization and symptoms of attention deficit hyperactivity disorder

BACKGROUND

Young children raised in institutions are exposed to extreme psychosocial deprivation that is associated with elevated risk for psychopathology and other adverse developmental outcomes. The prevalence of attention deficit hyperactivity disorder (ADHD) is particularly high in previously institutionalized children, yet the mechanisms underlying this association are poorly understood. We investigated whether deficits in executive functioning (EF) explain the link between institutionalization and ADHD.

METHOD

A sample of 136 children (aged 6-30 months) was recruited from institutions in Bucharest, Romania, and 72 never institutionalized community children matched for age and gender were recruited through general practitioners' offices. At 8 years of age, children's performance on a number of EF components (working memory, response inhibition and planning) was evaluated. Teachers completed the Health and Behavior Questionnaire, which assesses two core features of ADHD, inattention and impulsivity.

RESULTS

Children with history of institutionalization had higher inattention and impulsivity than community controls, and exhibited worse performance on working memory, response inhibition and planning tasks. Lower performances on working memory and response inhibition, but not planning, partially mediated the association between early institutionalization and inattention and impulsivity symptom scales at age 8 years.

CONCLUSIONS

Institutionalization was associated with decreased EF performance and increased ADHD symptoms. Deficits in working memory and response inhibition were specific mechanisms leading to ADHD in previously institutionalized children. These findings suggest that interventions that foster the development of EF might reduce risk for psychiatric problems in children exposed to early deprivation.

Early Adverse Experiences and the Developing Brain

Children exposed to various forms of adversity early in life are at increased risk for a broad range of developmental difficulties, affecting both cognitive and emotional adjustment. We review a growing body of evidence suggesting that exposure to adverse circumstances affects the developing brain in ways that increase risk for a myriad of problems. We focus on two forms of adversity, one in which children are exposed to childhood maltreatment in family environments, and another in which children are exposed to extreme psychosocial deprivation in contexts of institutional rearing. We discuss ways in which each of these experiences represent violations of species-expected caregiving conditions, thereby imposing challenges to the developing brain. We also review emerging data pointing to the effectiveness of early intervention in remediating neurodevelopmental consequences associated with maltreatment or institutional rearing. We conclude by discussing implications of this work for public health efforts and highlight important directions for the field.

Relation of Childhood Home Environment to Cortical Thickness in Late Adolescence: Specificity of Experience and Timing

What are the long-term effects of childhood experience on brain development? Research with animals shows that the quality of environmental stimulation and parental nurturance both play important roles in shaping lifelong brain structure and function. Human research has so far been limited to the effects of abnormal experience and pathological development. Using a unique longitudinal dataset of in-home measures of childhood experience at ages 4 and 8 and MRI acquired in late adolescence, we were able to relate normal variation in childhood experience to later life cortical thickness. Environmental stimulation at age 4 predicted cortical thickness in a set of automatically derived regions in temporal and prefrontal cortex. In contrast, age 8 experience was not predictive. Parental nurturance was not predictive at either age. This work reveals an association between childhood experience and later brain structure that is specific relative to aspects of experience, regions of brain, and timing.

Language development of internationally adopted children: Adverse early experiences outweigh the age of acquisition effect

We compared English language and cognitive skills between internationally adopted children (IA; mean age at adoption=2.24, SD=1.8) and their non-adopted peers from the US reared in biological families (BF) at two time points. We also examined the relationships between outcome measures and age at initial institutionalization, length of institutionalization, and age at adoption. On measures of general language, early literacy, and non-verbal IQ, the IA group performed significantly below their age-peers reared in biological families at both time points, but the group differences disappeared on receptive vocabulary and kindergarten concept knowledge at the second time point. Furthermore, the majority of children reached normative age expectations between 1 and 2 years post-adoption on all standardized measures. Although the age at adoption, age of institutionalization, length of institutionalization, and time in the adoptive family all demonstrated significant correlations with one or more outcome measures, the negative relationship between length of institutionalization and child outcomes remained most robust after controlling for the other variables. Results point to much flexibility and resilience in children's capacity for language acquisition as well as the potential primacy of length of institutionalization in explaining individual variation in IA children's outcomes.

LEARNING OUTCOMES

(1) Readers will be able to understand the importance of pre-adoption environment on language and early literacy development in internationally adopted children. (2) Readers will be able to compare the strength of the association between the length of institutionalization and language outcomes with the strength of the association between the latter and the age at adoption. (3) Readers will be able to understand that internationally adopted children are able to reach age expectations on expressive and receptive language measures despite adverse early experiences and a replacement of their first language with an adoptive language.

Deviations from the expectable environment in early childhood and emerging psychopathology

Current frameworks for understanding the link between early adverse childhood experiences and later negative life outcomes, including psychopathology, focus on the mediating negative impact on brain and biological systems in the developing child resulting broadly from stress and trauma. Although this approach is useful, we argue that the framework could be functionally extended by distinguishing the effects of two different types of abnormal input, both deviations from the expectable environment in early childhood. Specifically, we review the consequences of inadequate input (eg, neglect/deprivation) and harmful input (eg, abuse/trauma) on brain and biological development. We then review evidence on the differential links between each type of abnormal input to four selected domains of psychopathology (indiscriminate social behavior, posttraumatic stress disorder, attention-deficit/hyperactivity disorder, and conduct problems), and consider potential mechanisms for inadequate and harmful input to lead to these outcomes. We conclude that the careful consideration of the type of deviation from the expected environment, while acknowledging the practical difficulties in assessing this, is likely to lead to clearer understanding of the mechanism of risk for psychopathology, and that tailored approaches to prevention and intervention may be informed by considering the unique consequences of inadequate and harmful input when experienced in early childhood.

Early life stress and macaque amygdala hypertrophy: preliminary evidence for a role for the serotonin transporter gene

Background: Children exposed to early life stress (ELS) exhibit enlarged amygdala volume in comparison to controls. The primary goal of this study was to examine amygdala volumes in bonnet macaques subjected to maternal variable foraging demand (VFD) rearing, a well-established model of ELS. Preliminary analyses examined the interaction of ELS and the serotonin transporter gene on amygdala volume. Secondary analyses were conducted to examine the association between amygdala volume and other stress-related variables previously found to distinguish VFD and non-VFD reared animals.

Methods: Twelve VFD-reared and nine normally reared monkeys completed MRI scans on a 3T system (mean age = 5.2 years).

Results: Left amygdala volume was larger in VFD vs. control macaques. Larger amygdala volume was associated with: “high” cerebrospinal fluid concentrations of corticotropin releasing-factor (CRF) determined when the animals were in adolescence (mean age = 2.7 years); reduced fractional anisotropy (FA) of the anterior limb of the internal capsule (ALIC) during young adulthood (mean age = 5.2 years) and timid anxiety-like responses to an intruder during full adulthood (mean age = 8.4 years). Right amygdala volume varied inversely with left hippocampal neurogenesis assessed in late adulthood (mean age = 8.7 years). Exploratory analyses also showed a gene-by-environment effect, with VFD-reared macaques with a single short allele of the serotonin transporter gene exhibiting larger amygdala volume compared to VFD-reared subjects with only the long allele and normally reared controls.

Conclusion: These data suggest that the left amygdala exhibits hypertrophy after ELS, particularly in association with the serotonin transporter gene, and that amygdala volume variation occurs in concert with other key stress-related behavioral and neurobiological parameters observed across the lifecycle. Future research is required to understand the mechanisms underlying these diverse and persistent changes associated with ELS and amygdala volume.