Roads Diverged: Developmental Trajectories of Irritability From Toddlerhood Through Adolescence.

OBJECTIVE: Irritability is a dimensional trait that manifests from early life and is a robust transdiagnostic risk factor for psychopathology and impairment. A large, national dataset was leveraged to identify and broadly characterize trajectories from toddlerhood through adolescence, which is crucial for timely, targeted interventions. METHOD: Data on irritability and a broad array of potential factors affecting irritability development from 4,462 children assessed longitudinally at ages 3, 5, 9, and 15 were included. Latent class growth models identified groups of children based on their nonlinear irritability trajectories from toddlerhood to adolescence. LASSO regression then identified key characteristics differentiating trajectory groups. RESULTS: Five distinct irritability trajectories were identified, two of which were stable, maintaining medium or high irritability from age 3 to 15. Three trajectories showed undulating change over development, with an inflection point at the transition to adolescence (age 9): Most children had consistently low irritability. Two smaller groups started with high irritability at age 3 but diverged, sharply decreasing or increasing until a turning point at age 9. Developmental patterning of harsh/neglectful parenting and child internalizing symptoms most strongly differentiated trajectory groups. Sociodemographic characteristics, attachment style, neighborhood support, cognitive functioning, and genetic variation also differentiated trajectories. CONCLUSION: The results demonstrated the importance of the transition to adolescence as a critical inflection point for youths with fluctuating irritability trajectories. Identifying these patterns and multiple malleable factors associated with stably high or rising trajectories is an important step toward targeted interventions for the most vulnerable subgroups. DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented racial and/or ethnic groups in science. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented sexual and/or gender groups in science. One or more of the authors of this paper self-identifies as living with a disability. One or more of the authors of this paper received support from a program designed to increase minority representation in science. We actively worked to promote sex and gender balance in our author group. We actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our author group.