(PS12-4) Irritability Across Adolescence: Examining Longitudinal Trajectories, Stability, and Associations with Psychopathology and Functioning at Age 18

Irritability, marked by diminished frustration tolerance and temper outbursts, holds significant implications for youth mental health treatment. Despite prior research on irritability trajectories, understanding of individual differences during adolescence, a vulnerable period, remains limited. This study examines the measurement invariance, stability, and trajectory of irritability across adolescence (12-18 years), investigating associations with psychopathology and functioning at age 18. A community sample of families with 3-year-old children (N=518, 48.1% female) was recruited via commercial mailing lists and followed at 3-year intervals through adolescence. Irritability was assessed at ages 12, 15, and 18 using youth self-report on the Affective Reactivity Index (Stringaris et al., 2012). Semi-structured interviews were used to assess the major psychiatric disorders and social functioning. Measurement invariance analyses and latent growth curve modeling were conducted within a structural equation modeling (SEM) framework. Configural, metric, and scalar invariance models were supported. Elevated irritability (intercept) at age 12 predicted adverse outcomes at age 18, including poorer academic and interpersonal functioning, increased psychotropic medication use, mental health treatment, suicidal ideation, self-injury, and higher rates of depression, anxiety, disruptive behavior disorders, attention-deficit/hyperactivity disorder, and alcohol and/or drug disorders. Importantly, these associations persisted even after accounting for corresponding variables at age 12. The trajectory of irritability (slope) during early adolescence significantly predicted heightened risks for various outcomes at age 18, including suicidal ideation, depression, anxiety, disruptive behavior disorders, and poorer interpersonal functioning. Findings emphasize the crucial role of irritability's trajectory in influencing various psychopathological and functional outcomes in late adolescence and can inform intervention by identifying youth at highest risk during an already vulnerable stage of life.