Airborne Lead Exposure and Childhood Cognition: The Environmental Influences on Child Health Outcomes (ECHO) Cohort (2003-2022).

Objectives. To examine whether a previously reported association between airborne lead exposure and children's cognitive function replicates across a geographically diverse sample of the United States. Methods. Residential addresses of children (< 5 years) were spatially joined to the Risk-Screening Environmental Indicators model of relative airborne lead toxicity. Cognitive outcomes for children younger than 8 years were available for 1629 children with IQ data and 1476 with measures of executive function (EF; inhibitory control, cognitive flexibility). We used generalized linear models using generalized estimating equations to examine the associations of lead, scaled by interquartile range (IQR), accounting for individual- and area-level confounders. Results. An IQR increase in airborne lead was associated with a 0.74-point lower mean IQ score (b = -0.74; 95% confidence interval = -1.00, -0.48). The association between lead and EF was nonlinear and was modeled with a knot at the 97.5th percentile of lead in our sample. Lead was significantly associated with lower mean inhibitory control but not with cognitive flexibility. This effect was stronger among males for both IQ and inhibitory control. Conclusions. Early-life exposure to airborne lead is associated with lower cognitive functioning. (Am J Public Health. 2024;114(3):309-318. https://doi.org/10.2105/AJPH.2023.307519).

The effect of hair type and texture on electroencephalography and event-related potential data quality.

Research utilizing event-related potential (ERP) methods is generally biased with regard to sample representativeness. Among the myriad of factors that contribute to sample bias are researchers' assumptions about the extent to which racial differences in hair texture, volume, and style impact electrode placement, and subsequently, study eligibility. The current study examines these impacts using data collected from n = 213 individuals ages 17-19 years, and offers guidance on collection of ERP data across the full spectrum of hair types. Individual differences were quantified for hair texture using a visual scale, and for hair volume by measuring the amount of gel used in cap preparation. Electroencephalography data quality was assessed with multiple metrics at the preprocessing, post-processing, and variable generation stages. Results indicate that hair volume is associated with small, but systematic differences in signal quality and signal amplitude. Such differences are highly problematic as they could be misattributed to cognitive differences among groups. However, inclusion of gel volume as a covariate to account for individual differences in hair volume significantly reduced, and in most cases eliminated, group differences. We discuss strategies for overcoming real and perceived technical barriers for researchers seeking to achieve greater inclusivity and representativeness in ERP research.

Dynamic regulatory processes among child welfare parents: Temporal associations between physiology and parenting behavior.

This study examined how temporal associations between parents' physiological and behavioral responses may reflect underlying regulatory difficulties in at-risk parenting. Time-series data of cardiac indices (second-by-second estimates of inter-beat intervals - IBI, and respiratory sinus arrhythmia - RSA) and parenting behaviors were obtained from 204 child welfare-involved parents (88% mothers, Mage = 32.32 years) during child-led play with their 3- to 7-year-old children (45.1% female; Mage = 4.76 years). Known risk factors for maltreatment, including parents' negative social cognitions, mental health symptoms, and inhibitory control problems, were examined as moderators of intra-individual physiology-behavior associations. Results of ordinary differential equations suggested increases in parents' cardiac arousal at moments when they showed positive parenting behaviors. In turn, higher arousal was associated with momentary decreases in both positive and negative parenting behaviors. Individual differences in these dynamic processes were identified in association with parental risk factors. In contrast, no sample-wide RSA-behavior associations were evident, but a pattern of increased positive parenting at moments of parasympathetic withdrawal emerged among parents showing more total positive parenting behaviors. This study illustrated an innovative and ecologically-valid approach to examining regulatory patterns that may shape parenting in real-time and identified mechanisms that should be addressed in interventions.

A dynamic systems account of parental self-regulation processes in the context of challenging child behavior.

To advance the understanding of how parental self-regulation contributes to their role in supporting children's development, this study proposes a model of the dynamic processes involved in parental self-regulation. Based on time-series data from 157 mothers and their 30- to 60-month-old children (49.7% female; 96% White; data collected June 2017-December 2019 in central Pennsylvania, U.S.) during a challenging wait task, the model was tested by examining the temporal relations among challenging child behavior, maternal physiology, and maternal responsiveness. Results were consistent with the hypothesized dynamic negative feedback processes and revealed their associations with the overall quality of parenting behaviors and experiences. Findings elucidate how parents adapt to competing external (attending to child) and internal (restoring parents' equilibrium) demands during parenting challenges.

The reliability of visual ERP components in children across the first year of school.

Event-related potentials (ERPs) are increasingly used as neurophysiological markers of perceptual and cognitive processes conveying risk for psychopathology. However, little is known about the reliability of ERP components during childhood, a time of substantial brain maturation. In the present study, we examine the early visual ERP components (P1, N170, VPP), frequently examined as indicators of attentional bias, for 110 children at kindergarten (T1) and first grade (T2). Children performed a Go/Nogo task at both time points, with exact stimuli changed to reduce habituation. All components showed increases in absolute amplitude and the P1 and VPP also showed decreases in latency. Retest reliability across time was good to very good for amplitude measures (Pearson rs ranging from .54 for N170 to .69 for P1) and low to very good for latencies (rs from .34 for P1 to .60 for N170), despite the change in visual stimuli. Although there was some evidence of moderation by sex, early visual ERP components appear to be a reliable measure of individual differences in attention processing in middle childhood. This has implications for the use of early visual ERP components as trait-like markers for individual differences in perceptual processes in developmental research.

Conducting Event-Related Potential (ERP) Research with Young Children: A Review of Components, Special Considerations and Recommendations for Research on Cognition and Emotion.

There has been an unprecedented increase in the number of research studies employing event-related potential (ERP) techniques to examine dynamic and rapidly-occurring neural processes with children during the preschool and early childhood years. Despite this, there has been little discussion of the methodological and procedural differences that exist for studies of young children versus older children and adults. That is, reviewers, editors, and consumers of this work often expect developmental studies to simply apply adult techniques and procedures to younger samples. Procedurally, this creates unrealistic expectations for research paradigms, data collection, and data reduction and analyses. Scientifically, this leads to inappropriate measures and methods that hinder drawing conclusions and advancing theory. Based on ERP work with preschoolers and young children from 10 laboratories across North America, we present a summary of the most common ERP components under study in the area of emotion and cognition in young children along with 13 realistic expectations for data collection and loss, laboratory procedures and paradigms, data processing, ERP averaging, and typical challenges for conducting this type of work. This work is intended to supplement previous guidelines for work with adults and offer insights to aid researchers, reviewers, and editors in the design and evaluation of developmental research using ERPs. Here we make recommendations for researchers who plan to conduct or who are conducting ERP studies in children between ages 2 and 12, focusing on studies of toddlers and preschoolers. Recommendations are based on both data and our cumulative experience and include guidelines for laboratory setup, equipment and recording settings, task design, and data processing.

When you go low, I go high: Negative coordination of physiological synchrony among parents and children.

The parent-child relationship is an important context for children's emotional development. The current study assessed 43 parent-child dyads while watching a positive film clip and a negative film clip, in order to examine whether partner's physiological reactivity demonstrated dyadic synchrony, and whether this was associated with children's prosocial empathy. Respiratory sinus arrhythmia was measured in both caretakers and children (ages 9-14) and a continuous time series was estimated in order to maximize temporal resolution of physiological dynamics. Dyads varied in both the magnitude and direction of synchrony, with correlation coefficients ranging from moderately negative; r = -.44 (increases in one partner correspond to decreases in the other), to moderately positive; r = .55 (increases in one partner correspond to increases in the other). For both conditions, negative synchrony was correlated with higher child-reported empathy. For the negative mood condition, this effect was moderated by caretaker's emotional acceptance such that positive synchrony was associated with lower levels of empathy among dyads in which caretaker emotional acceptance was lower. These results suggest that positive physiological synchrony during a negative mood condition may not be adaptive for children when their caretaker lacks the skills to appropriately socialize their child's emotional development.

Magnitude and Chronicity of Environmental Smoke Exposure Across Infancy and Early Childhood in a Sample of Low-Income Children.

INTRODUCTION: Infants and young children may be at an increased risk for second- and thirdhand exposure to tobacco smoke because of increased respiration rate and exposure to surface residue. However, relatively fewer studies have examined biomarkers of exposure (cotinine) in children under age 4 years. This study examines the magnitude and chronicity of exposure across early childhood among children from low-income families in order to better characterize contextual risk factors associated with exposure. METHODS: A total of 1292 families were recruited in six nonurban counties of Pennsylvania and North Carolina. Cotinine was assayed from infant saliva at 6, 15, 24, and 48 months of age (N = 1218), and categorized as low (≤0.45 ng/mL), moderate (0.46-12 ng/mL), or high (≥12 ng/mL) at each time point. Categories were highly correlated across time. Latent class analysis was used to summarize patterns of exposure categories across time. RESULTS: Magnitude of exposure in this sample was high, with approximately 12% of infants registering cotinine values at least 12 ng/mL, consistent with active smoking in adults. Greater exposure was associated with lower income, less education, more residential instability, and more instability in adult occupants in the home, whereas time spent in center-based day care was associated with lower exposure. CONCLUSIONS: Young children from low-income, nonurban communities appear to bear a higher burden of secondhand smoke exposure than previous studies have reported. Results contribute to understanding populations at greater risk, as well as specific, potentially malleable, environmental factors that may be examined as direct contributors to exposure. IMPLICATIONS: Results suggest that infants from low-income, nonurban families have higher risk for environmental smoke exposure than data from nationally representative samples. Predictors of exposure offer insights into specific factors that may be targeted for risk reduction efforts, specifically conditions of children's physical space. In addition to considering the increases in risk when an adult smoker lives in a child's home, families should also attend to the possible risk embedded within the home itself, such as residual smoke from previous occupants. For high-risk children, day care appears to mitigate the magnitude of exposure by providing extended time in a smoke-free environment.

The association between perinatal hypoxia exposure and externalizing symptoms and children's decision making in conditions of uncertainty is moderated by DRD2 genotype.

Variants of the DRD2 Taq1A polymorphism, which have been shown to result in functional differences in dopamine D2 receptors (D2R), have been linked to various externalizing outcomes in adults. However, the neurobiological processes that contribute to these associations are not well understood. The current study investigates gene × environment effects on teacher-rated externalizing behaviors and probabilistic decision making in a sample of 333 children (age 9) enrolled in an ongoing longitudinal study. Findings indicate that externalizing behaviors increased as a function of hypoxic exposure only among individuals carrying the A1 (A1+) allele. Results also indicate that willingness to pursue reward under conditions of maximum uncertainty (50% probability) decreased as a function of hypoxic exposure only among A1- individuals. Among A1 carriers, no association between probability decision making and hypoxic exposure emerged. These findings suggest that hypoxia could influence neural development through different biological pathways depending on D2 receptor genotype, and provide insight into the development of individual differences in behavior and decision making.

Quantifying respiratory sinus arrhythmia: Effects of misspecifying breathing frequencies across development.

Low resting respiratory sinus arrhythmia (RSA), and to a lesser extent excessive RSA reactivity to emotion evocation, are observed in many psychiatric disorders characterized by emotion dysregulation, including syndromes spanning the internalizing and externalizing spectra, and other conditions such as nonsuicidal self-injury. Nevertheless, some inconsistencies exist. For example, null outcomes in studies of RSA-emotion dysregulation relations are sometimes observed among younger participants. Such findings may derive from use of age inappropriate frequency bands in calculating RSA. We combine data from five published samples (N = 559) spanning ages 4 to 17 years, and reanalyze RSA data using age-appropriate respiratory frequencies. Misspecifying respiratory frequencies results in overestimates of resting RSA and underestimates of RSA reactivity, particularly among young children. Underestimates of developmental shifts in RSA and RSA reactivity from preschool to adolescence were also observed. Although correlational analyses revealed weak negative associations between resting RSA and aggression, those with clinical levels of externalizing exhibited lower resting RSA than their peers. No associations between RSA reactivity and externalizing were observed. Results confirm that age-corrected frequency bands should be used when estimating RSA, and that literature-wide overestimates of resting RSA, underestimates of RSA reactivity, and underestimates of developmental shifts in RSA and RSA reactivity may exist.

The dynamics of internalizing and externalizing comorbidity across the early school years.

High rates of comorbidity are observed between internalizing and externalizing problems, yet the developmental dynamics of comorbid symptom presentations are not yet well understood. This study explored the developmental course of latent profiles of internalizing and externalizing symptoms across kindergarten, first grade, and second grade. The sample consisted of 336 children from an urban, low-income community, selected based on relatively high (61%) or low (39%) aggressive/oppositional behavior problems at school entry (64% male; 70% African American, 20% Hispanic). Teachers reported on children's symptoms in each year. An exploratory latent profile analysis of children's scores on aggression/oppositionality, hyperactivity/inattention, anxiety, and social withdrawal symptom factors revealed four latent symptom profiles: comorbid (48% of the sample in each year), internalizing (19%-23%), externalizing (21%-22%), and well-adjusted (7%-11%). The developmental course of these symptom profiles was examined using a latent transition analysis, which revealed remarkably high continuity in the comorbid symptom profile (89% from one year to the next) and moderately high continuity in both the internalizing and externalizing profiles (80% and 71%, respectively). Internalizing children had a 20% probability of remitting to the well-adjusted profile by the following year, whereas externalizing children had a 25% probability of transitioning to the comorbid profile. These results are consistent with the hypothesis that a common vulnerability factor contributes to developmentally stable internalizing-externalizing comorbidity, while also suggesting that some children with externalizing symptoms are at risk for subsequently accumulating internalizing symptoms.

Implications of ongoing neural development for the measurement of the error-related negativity in childhood.

Event-related potentials (ERPs) have been proposed as biomarkers capable of reflecting individual differences in neural processing not necessarily detectable at the behavioral level. However, the role of ERPs in developmental research could be hampered by current methodological approaches to quantification. ERPs are extracted as an average waveform over many trials; however, actual amplitudes would be misrepresented by an average if there was high trial-to-trial variability in signal latency. Low signal temporal consistency is thought to be a characteristic of immature neural systems, although consistency is not routinely measured in ERP research. The present study examined the differential contributions of signal strength and temporal consistency across trials in the error-related negativity (ERN) in 6-year-old children, as well as the developmental changes that occur in these measures. The 234 children were assessed annually in kindergarten, 1st, and 2nd grade. At all assessments signal strength and temporal consistency were highly correlated with the average ERN amplitude, and were not correlated with each other. Consistent with previous findings, ERN deflections in the averaged waveform increased with age. This was found to be a function of developmental increases in signal temporal consistency, whereas signal strength showed a significant decline across this time period. In addition, average ERN amplitudes showed low-to-moderate stability across the three assessments whereas signal strength was highly stable. In contrast, signal temporal consistency did not evidence rank-order stability across these ages. Signal strength appears to reflect a stable individual trait whereas developmental changes in temporal consistency may be experientially influenced.

Children's parasympathetic reactivity to specific emotions moderates response to intervention for early-onset aggression.

Following theories that individual differences in respiratory sinus arrhythmia (RSA) denote differential sensitivity to environmental influences, this study examines whether differences in RSA reactivity to specific emotional challenges predict differential response to intervention. We present data from a randomized clinical trial of a targeted intervention for early onset aggression. In collaboration with a high-risk urban school district, 207 kindergarten children (73% African American, 66% male), identified by their teachers as having high levels of aggressive and disruptive behavior, were recruited. All children received a universal social-emotional curriculum. One hundred children were randomly assigned to an additional intervention consisting of weekly peer-based social skills training. Complete RSA data were available for 139 of the children. Teacher-reported externalizing symptoms and emotion regulation in 1st grade (post intervention) were examined controlling for baseline levels. First-grade peer nominations of aggressive behavior, controlling for baseline nominations, were also examined as outcomes. No effect of resting RSA was found. However, greater reactivity to anger was associated with higher externalizing symptoms and lower emotion regulation skills in 1st grade relative to low reactive children. Lower reactivity to fear was associated with greater improvement over time, an effect that was enhanced in the targeted intervention condition. Results suggest that measures of affective reactivity may provide insight into children's capacity to benefit from different types of interventions.

The role of resting frontal EEG asymmetry in psychopathology: afferent or efferent filter?

Resting EEG asymmetry evident early in life is thought to bias affective behaviors and contribute to the development of psychopathology. However, it remains unclear at what stage of information processing this bias occurs. Asymmetry may serve as an afferent filter, modulating emotional reactivity to incoming stimuli; or as an efferent filter, modulating behavioral response tendencies under emotional conditions. This study examines 209 kindergarten children (M = 6.03 years old) to test predictions put forth by the two models. Resting asymmetry was examined in conjunction with electrodermal and cardiac measures of physiological reactivity to four emotion-inducing film clips (fear, sad, happy, anger) and teacher ratings of psychopathology. Results confirm an association between increased right side cortical activation and internalizing symptom severity as well as left activation and externalizing symptom severity. Significant interactions between resting asymmetry and physiological reactivity to emotion indicate that physiological reactivity moderates the association between resting asymmetry and symptoms of psychopathology.

Early adversity, RSA, and inhibitory control: evidence of children's neurobiological sensitivity to social context.

This study examined parasympathetic physiology as a moderator of the effects of early adversity (i.e., child abuse and neglect) on children's inhibitory control. Children's respiratory sinus arrhythmia (RSA) was assessed during a resting baseline, two joint challenge tasks with mother, and an individual frustration task. RSA assessed during each of the joint parent-child challenge tasks moderated the effects of child maltreatment (CM) status on children's independently-assessed inhibitory control. No moderation effect was found for RSA assessed at baseline or in the child-alone challenge task. Among CM-exposed children, lower RSA levels during the joint task predicted the lowest inhibitory control, whereas higher joint task RSA was linked to higher inhibitory control scores that were indistinguishable from those of non-CM children. Results are discussed with regard to the importance of considering context specificity (i.e., individual and caregiver contexts) in how biomarkers inform our understanding of individual differences in vulnerability among at-risk children.

Associations between respiratory sinus arrhythmia reactivity and internalizing and externalizing symptoms are emotion specific.

Internalizing and externalizing disorders are often, though inconsistently in studies of young children, associated with low baseline levels of respiratory sinus arrhythmia (RSA). RSA is thus considered to reflect the capacity for flexible and regulated affective reactivity and a general propensity for psychopathology. However, studies assessing RSA reactivity to emotional challenges tend to report more consistent associations with internalizing than with externalizing disorders, although it is unclear whether this is a function of the type of emotion challenges used. In the present study, we examined whether baseline RSA was associated with internalizing and/or externalizing severity in a sample of 273 young children (ages 5-6) with elevated symptoms of psychopathology. Following motivation-based models of emotion, we also tested whether RSA reactivity during withdrawal-based (fear, sadness) and approach-based (happiness, anger) emotion inductions was differentially associated with internalizing and externalizing symptoms, respectively. Baseline RSA was not associated with externalizing or internalizing symptom severity. However, RSA reactivity to specific emotional challenges was associated differentially with each symptom domain. As expected, internalizing symptom severity was associated with greater RSA withdrawal (increased arousal) during fearful and sad film segments. Conversely, externalizing symptom severity was related to blunted RSA withdrawal during a happy film segment. The use of theoretically derived stimuli may be important in characterizing the nature of the deficits in emotion processing that differentiate the internalizing and externalizing domains of psychopathology.

The role of strategy-use and parasympathetic functioning in maternal emotion regulation.

Research has recognized that parental emotion regulation influences whether parents respond sensitively to their children in challenging parenting situations. However, parental emotion regulation is usually assessed using questionnaires that are not about parenting, rather than through examining parents' reaction to specific parenting situations that might evoke negative emotions. This study investigates individual differences in mothers' emotion regulation during parenting, specifically examining the relation between their subjective negative emotions and observed parenting behaviors and whether this relation is moderated by cognitive (strategies to manage negative emotions) and physiological (resting baseline and reactivity of respiratory sinus arrhythmia; RSA) processes. Data of 157 mothers' self-reported negative emotions and strategy-use, their RSA, observed maternal responsiveness, and their preschool-age children's (30-60 months, 49.7% female) challenging behaviors were collected during a Wait Task, in which mothers told children to wait before opening an appealing gift. Regression analysis indicated that, after controlling for how challenging children were, mothers' level of negative emotion was not associated with observed level of maternal responsiveness. In line with hypotheses, the association was moderated by mothers' resting RSA and the extent to which they suppressed negative emotions. However, contrary to hypotheses, the association was not moderated by use of reappraisal, distraction, or rumination, or RSA reactivity. The significant findings suggest that, although mothers' subjective experiences of negative emotions are not necessarily related to less responsive parenting behaviors, the link between maternal emotions and parenting behavior may indicate differences in how mothers engage cognitive strategies as well as their physiological regulation capacity. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Environmental tobacco smoke exposure is associated with increased levels of metals in children's saliva.

BACKGROUND: Exposure to environmental tobacco smoke (ETS) has been associated with detectable levels of cotinine (a nicotine metabolite) in children's saliva. However, tobacco smoke also contains toxic and essential trace metals, including chromium (Cr), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn). OBJECTIVE: The current study examines whether there is a relationship between ETS exposure, as gauged by salivary cotinine, and salivary levels of these metals in a subset (n = 238) of children from the Family Life Project. METHODS: Using inductively-coupled-plasma optical emission spectrophotometry, we measured levels of metals in saliva from children at ~90 months of age. Salivary cotinine was measured using a commercial immunoassay. RESULTS: We found that Cr, Cu, Mn, and Zn were detected in most samples (85-99%) with lower levels of detection for Pb and Ni (9.3% and 13.9% respectively). There were no significant differences in any of the metal concentrations between males and females, nor were levels associated with body mass index, although significant differences in salivary Cr and Mn by race, state and income-to-needs ratio were observed. Children with cotinine levels >1 ng/ml had higher levels of Zn (b = 0.401, 95% CI: 0.183 to 0.619; p = 0.0003) and Cu (b = 0.655, 95% CI: 0.206 to 1.104; p = 0.004) compared to children with levels <1 ng/ml, after controlling for multiple confounders, including sex, race, BMI and income-to-needs ratio. Further, we show that children whose cotinine levels were >1 µg/L were more likely to have detectable levels of Pb in their saliva (b = 1.40, 95% CI: 0.424 to 2.459; p = 0.006) compared to children with cotinine levels <1 ng/ml, also considering confounders. IMPACT STATEMENT: This is the first study to demonstrate significant associations between salivary cotinine and salivary levels of Cu, Zn and Pb, suggesting that environmental tobacco smoke exposure my be one source of increased children's exposure to heavy metals. This study also demonstrates that saliva samples can be used to measure heavy metal exposure, and thus serve as a non-invasive tool for assessing a broader range of risk indicators.

Instantiating the multiple levels of analysis perspective in a program of study on externalizing behavior.

During the last quarter century, developmental psychopathology has become increasingly inclusive and now spans disciplines ranging from psychiatric genetics to primary prevention. As a result, developmental psychopathologists have extended traditional diathesis-stress and transactional models to include causal processes at and across all relevant levels of analysis. Such research is embodied in what is known as the multiple levels of analysis perspective. We describe how multiple levels of analysis research has informed our current thinking about antisocial and borderline personality development among trait impulsive and therefore vulnerable individuals. Our approach extends the multiple levels of analysis perspective beyond simple Biology × Environment interactions by evaluating impulsivity across physiological systems (genetic, autonomic, hormonal, neural), psychological constructs (social, affective, motivational), developmental epochs (preschool, middle childhood, adolescence, adulthood), sexes (male, female), and methods of inquiry (self-report, informant report, treatment outcome, cardiovascular, electrophysiological, neuroimaging). By conducting our research using any and all available methods across these levels of analysis, we have arrived at a developmental model of trait impulsivity that we believe confers a greater understanding of this highly heritable trait and captures at least some heterogeneity in key behavioral outcomes, including delinquency and suicide.

Aggression as an equifinal outcome of distinct neurocognitive and neuroaffective processes.

Early onset aggression precipitates a cascade of risk factors, increasing the probability of a range of externalizing and internalizing psychopathological outcomes. Unfortunately, decades of research on the etiological contributions to the manifestation of aggression have failed to yield identification of any risk factors determined to be either necessary or sufficient, likely attributable to etiological heterogeneity within the construct of aggression. Differential pathways of etiological risk are not easily discerned at the behavioral or self-report level, particularly in young children, requiring multilevel analysis of risk pathways. This study focuses on three domains of risk to examine the heterogeneity in 207 urban kindergarten children with high levels of aggression: cognitive processing, socioemotional competence and emotion processing, and family context. The results indicate that 90% of children in the high aggression group could be characterized as either low in verbal ability or high in physiological arousal (resting skin conductance). Children characterized as low verbal, high arousal, or both differed in social and emotional competence, physiological reactivity to emotion, and aspects of family-based contextual risk. The implications of this etiologic heterogeneity of aggression are discussed in terms of assessment and treatment.