Poster #23 - Genetic and Environmental Contributions to Developmental Patterns of Irritability in the Preschool Period

• In Event: Poster Session 10

Abstract

Irritability, conceptualized as the tendency to experience anger and to show a low threshold for frustration, is associated with internalizing and externalizing psychopathology (Leibenluft & Stoddard, 2013). Irritability peaks during the preschool period and declines as children gain better executive function capacities and social competences that facilitate emotion regulation (e.g., Wakschlag et al., 2018). The heritability of irritability is approximately 30% to 40% and is stable across middle childhood and adolescence (e.g., Stringaris et al., 2012). However, there is a lack of attention regarding the etiology and development of irritability in the preschool period—a time when it is most prevalent. The present study examined the genetic and environmental influences on both rank-order and mean-level stability and change in irritability in preschoolers.

Methods. The sample was comprised 310 same-sex twin pairs (MZ = 123; DZ = 187) longitudinally assessed in ages 3, 4 and 5. Irritability was assessed using 4 items from the Child Behavior Checklist 11/2 – 5 (Achenback & Rescorla, 2000; Wiggins et al., 2014) rated by primary caregivers. Biometric Cholesky models and latent growth curve models (LGCM) were used to examine the genetic and environmental influences on the development of irritability from ages 3 to 5. Specifically, biometric Cholesky models capture genetic and environmental contributions to rank-order stability and change, while biometric LGCM can estimate genetic and environmental contributions to the absolute mean-level rate of change across the development.

Results. Irritability was stable across age (rs ranging from .53 to .64). Genetic influences contributed to 53%, 59% and 61% of the variances at ages 3, 4 and 5 respectively, and nonshared environmental influences (i.e., accidents, differential parenting, etc.) accounted for the remaining variance. While there were genetic and nonshared environmental influences that persisted across age (and contribute to stability), there were also novel genetic and environmental effects that emerged at ages 4 and 5 indicating genetic and environmental contributions to rank-order change (Figure 1). LGCM (Figure 2) revealed that irritability scores declined across age (µs = -0.12, p < .01). The initial level of irritability (i.e., intercept) was accounted for by genetic influences (61.9%) and nonshared environmental effects (38.1%). In contrast, only nonshared environmental influences significantly contributed to the direction and rate of change (i.e., slope).

Discussion. The present study shows that irritability stability is influenced by both genetic and nonshared environmental factors. Rank-order change is explained by genetic and nonshared environmental factors, whereas the mean-level rate of change is only due to nonshared environments. Thus, different processes underlie the two types of developmental change emphasize the need to consider both for fuller picture of child development. The finding that child-specific environmental factors account for change in irritability suggests that irritability is malleable and early interventions can reroute developmental trajectories, especially for those who may be genetically predisposed to show higher levels of irritability.

Authors

• I-Tzu Hung, Boston University
  Presenting Author

• Chang Liu, George Washington University

• Jody M. Ganiban, George Washington University

• Kimberly J Saudino, Boston University