Inhibitory Control in Early Childhood Aggression Subtypes: Mediation by Irritability

Genetic and Environmental Influences on the Development of Irritability from Ages 3 to 5 Years

OBJECTIVE

Irritability is genetically influenced and is associated with internalizing and externalizing psychopathology. However, little is known about the etiology of the development of irritability in the preschool period. The present study examined this from rank-order stability and developmental trajectories perspectives.

METHOD

The irritability of 310 same-sex twin pairs (monozygotic = 123; dizygotic = 187; 51% female) was longitudinally assessed at ages 3, 4 and 5 years via parent-reports on the Child Behavior Checklist. Biometric Cholesky models and latent growth curve models were used to examine genetic and environmental influences on both the rank-order stability and instability, and within individual changes in levels of irritability across age (i.e. developmental trajectories), respectively.

RESULTS

The heritability of irritability ranged from 53% to 60%, with the remaining variances explained by nonshared environmental influences. Age-to-age stability was largely due to genetic influences. Novel genetic and nonshared environmental effects emerged at ages 4 and 5, indicating genetic and environmental contributions to instability. Approximately 42% and 22% of genetic influences at ages 4 and 5, respectively, were independent of prior ages, and over 85% of nonshared environmental influences were age-specific. Individual differences in developmental trajectories of irritability were entirely due to nonshared environmental influences.

CONCLUSIONS

The rank-order stability of irritability and within-individual change in levels of irritability across age are governed by different etiological processes, emphasizing the importance of examining development from multiple perspectives. Both perspectives highlight the role of nonshared environmental factors in early irritability development. Interventions could benefit from leveraging these factors to redirect early irritability development.

Neural Correlates of Irritability and Potential Moderating Effects of Inhibitory Control

Background

Irritability affects up to 20% of youth and is a primary reason for referral to pediatric mental health clinics. Irritability is thought to be associated with disruptions in processing of reward, threat, and cognitive control; however, empirical study of these associations at both the behavioral and neural level have yielded equivocal findings that may be driven by small sample sizes and differences in study design. Associations between irritability and brain connectivity between cognitive control and reward- or threat-processing circuits remain understudied. Furthermore, better inhibitory control has been linked to lower irritability and differential neural functioning among irritable youth, suggesting that good inhibitory control may serve as a protective factor.

Methods

We hypothesized that higher irritability scores would be associated with less positive (or negative) connectivity between cognitive control and threat-processing circuits and between cognitive control and reward-processing circuits in the Healthy Brain Network dataset (release 10.0; N = 4135). We also hypothesized that these associations would be moderated by inhibitory control such that weaker associations between irritability and connectivity would be detected in youths with better than with worse inhibitory control. Regression models were used to test whether associations between irritability and between-network connectivity were moderated by inhibitory control.

Results

Counter to our hypothesis, we detected higher irritability associated with reduced connectivity between threat- and reward-processing and cognitive control networks only in 5- to 9-year-old boys. Inhibitory control did not moderate associations of irritability with between-network connectivity.

Conclusions

Exploratory findings indicate that reduced between-network connectivity may underlie difficulty regulating negative emotions, leading to greater irritability.

Understanding irritability through the lens of self-regulatory control processes in children and adolescents: a systematic review

Among youths, pathological irritability is highly prevalent and severely disabling. As a frequent symptom, it often leads to referrals to child and adolescent mental health services. Self-regulatory control (SRC) processes are a set of socio-psycho-physiological processes that allow individuals to adapt to their ever-changing environments. This conceptual framework may enhance the current understanding of the cognitive, emotional, behavioural and social dysregulations underlying irritability. The present systematic review (PROSPERO registration: #CRD42022370390) aims to synthesize existing studies that examine irritability through the lens of SRC processes among youths (< 18 years of age). We conducted a comprehensive literature search among six bibliographic databases: Embase.com, Medline ALL Ovid, APA PsycInfo Ovid, Web of Science Core Collection, the Cochrane Database of Systematic Reviews Wiley and ProQuest Dissertations & Theses A&I. Additional searches were performed using citation tracing strategies. The retrieved reports totalled 2612, of which we included 82 (i.e., articles) from 74 studies. More than 85% of reports were published during the last 6 years, highlighting the topicality of this work. The studies sampled n = 26,764 participants (n = 12,384 girls and n = 12,905 boys, n = 1475 no information) with an average age of 8.08 years (SD = 5.26). The included reports suggest that irritability has an association with lower effortful control, lower cognitive control and delay intolerance. Further, evidence indicates both cross-sectional and longitudinal associations between irritability and a lack of regulation skills for positive and negative emotions, particularly anger. Physiological regulation seems to moderate the association between irritability and psychopathology. Finally, the mutual influence between a child's irritability and parenting practice has been established in several studies. This review uses the lens of SRC to illustrate the current understanding of irritability in psychopathology, discusses important gaps in the literature, and highlights new avenues for further research.

Neural mechanisms of inhibitory control in preadolescent irritability: Insights from the ABCD study

OBJECTIVE

Elevated pediatric irritability is a transdiagnostic symptom that predicts multiple mental health problems in adolescence and adulthood. Altered top-down regulatory networks, such as inhibitory control networks that suppress an impulse in favor of goal-directed behavior, are thought to contribute to high levels of youth irritability. Nevertheless, little work has examined links between youth irritability and neural processes supporting inhibitory control in large diverse samples, nor have they focused on the key period ramping up to adolescence (i.e., preadolescence).

METHOD

Functional MRI data from 5380 preadolescents (age M=9.97 years, SD=0.62) in the baseline Adolescent Brain and Cognitive Development (ABCD) Study were analyzed. Parents reported on their preadolescent's irritability. The stop signal task (SST) was leveraged to probe successful and failed inhibitory control. Activation and functional connectivity with amygdala, ventral striatum, and prefrontal seed regions were calculated during the SST and used in whole brain and region of interest (ROI) group-level analyses evaluating irritability effects.

RESULTS

Preadolescents with higher levels of irritability displayed decreases in functional connectivity among amygdala, ventral striatum, and prefrontal cortex regions during both successful and failed inhibitory control conditions. These results remained after adjusting for co-occurring anxiety, depression, and attention-deficit/hyperactivity symptoms.

CONCLUSIONS

Findings suggest neural aberrations in inhibitory control play a role in the pathophysiology of preadolescent irritability and associations are not merely due to co-occurring symptoms. Neural mechanisms of inhibitory control associated with irritability may provide novel intervention targets.

Multivariate Assessment of Inhibitory Control in Youth: Links With Psychopathology and Brain Function

Inhibitory control is central to many theories of cognitive and brain development, and impairments in inhibitory control are posited to underlie developmental psychopathology. In this study, we tested the possibility of shared versus unique associations between inhibitory control and three common symptom dimensions in youth psychopathology: attention-deficit/hyperactivity disorder (ADHD), anxiety, and irritability. We quantified inhibitory control using four different experimental tasks to estimate a latent variable in 246 youth (8-18 years old) with varying symptom types and levels. Participants were recruited from the Washington, D.C., metro region. Results of structural equation modeling integrating a bifactor model of psychopathology revealed that inhibitory control predicted a shared or general psychopathology dimension, but not ADHD-specific, anxiety-specific, or irritability-specific dimensions. Inhibitory control also showed a significant, selective association with global efficiency in a frontoparietal control network delineated during resting-state functional magnetic resonance imaging. These results support performance-based inhibitory control linked to resting-state brain function as an important predictor of comorbidity in youth psychopathology.

Affective Contributions to Instrumental and Reactive Aggression in Middle Childhood: Variable- and Person-Centered Approaches

OBJECTIVE

Research on the role of affect in childhood aggression motives has largely focused on domain-level affective traits. Lower-order affective facets may show more distinct relationships with instrumental and reactive aggression - at both the variable and individual levels - and offer unique insights into whether and how several forms of affect are involved in aggression motives.

METHOD

Caregivers (98% mothers) of 342 children (Mage = 9.81 years, 182 girls, 31% White) reported on children's aggression and affect-relevant personality traits, personality pathology, and callous-unemotional traits.

RESULTS

Both reactive and instrumental aggressions were characterized by higher levels of trait irritability, fear, withdrawal, sadness, and callous-unemotional traits in zero-order analyses. Instrumental aggression was characterized by low trait positive emotions. Reactive aggression was uniquely associated with irritability, fear, withdrawal, and sadness, whereas instrumental aggression was uniquely associated with callous-unemotional traits and (low) positive emotions. Groups identified by latent profile analyses were differentiated only by aggression severity.

CONCLUSIONS

The findings support both the similarity and distinction of reactive and instrumental aggression vis-à-vis their affective phenomenology. Consistent with existing theories, reactive aggression was linked to multiple forms of negative emotionality, whereas instrumental aggression was linked to higher levels of callous-unemotional traits. In a novel finding, instrumental aggression was uniquely characterized by lower positive emotions. The findings highlight the utility of pre-registered approaches employing comprehensive personality-based affective frameworks to organize and understand similarities and differences between aggression functions.

Developmental Trajectories of Irritability across the Transition to Toddlerhood: Associations with Effortful Control and Psychopathology

Preschool-age irritability is a transdiagnostic marker of internalizing and externalizing problems. However, researchers have generally been reluctant to examine irritability within a clinically salient framework at younger ages due to some instability during the "terrible twos" period. Developmentally sensitive and dense measurements to capture intra- and inter-individual variability, as well as exploration of developmental processes that predict change, are needed. This study aimed to examine (1) the trajectories of irritability at the transition to toddlerhood (12-24 months of age) using repeated measures, (2) whether effortful control was associated with individual differences in level and growth rate of irritability, and (3) whether individual differences in the irritability trajectories were associated with later psychopathology. Families were recruited when the child was 12-18 months old (N = 333, 45.65% female). Mothers reported on their toddler's irritability at baseline and every two months until a follow-up laboratory assessment approximately one year later. Effortful control was measured at baseline. Clinical internalizing/externalizing symptoms were measured at the follow-up assessment. Hierarchical linear models revealed an increase in irritability over time, yet there was relatively little within-person variability. Effortful control was only associated with the level of irritability and not growth rate. Level of irritability was associated with internalizing, externalizing, and combined symptoms, but growth rate was not. Findings suggest intraindividual stability in irritability at the transition to toddlerhood and the possibility that screening for elevated irritability at toddler age is meaningful.

White matter integrity in adolescent irritability: A preliminary study

Irritability is a prevalent, impairing transdiagnostic symptom, especially during adolescence, yet little is known about irritability's neural mechanisms. A few studies examined the integrity of white matter tracts that facilitate neural communication in irritability, but only with extreme, disorder-related symptom presentations. In this preliminary study, we used a group connectometry approach to identify white matter tracts correlated with transdiagnostic irritability in a community/clinic-based sample of 35 adolescents (mean age = 14 years, SD = 2.0). We found positive and negative associations with irritability in local white matter tract bundles including sections of the longitudinal fasciculus; frontoparietal, parolfactory, and parahippocampal cingulum; corticostriatal and thalamocortical radiations; and vertical occipital fasciculus. Our findings support functional neuroimaging studies that implicate widespread neural pathways, particularly emotion and reward networks, in irritability. Our findings of positive and negative associations reveal a complex picture of what is "good" white matter connectivity. By characterizing irritability's neural underpinnings, targeted interventions may be developed.