Adolescents' pathological personality traits, mentalizing, and daily social interactions linking Criteria A and B from the DSM-5 alternative model for personality disorders.

Personality pathology often emerges in adolescence-a period marked by increasing autonomy and complex peer dynamics-but its moment-to-moment interpersonal expression remains poorly understood. This preregistered, multi-informant ambulatory assessment study tracked 294 adolescents (58.5% female; ages 12-21) across 13,190 real-world interactions over 14 days. Using the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, alternative model for personality disorders, we examined how maladaptive traits (Criterion B) relate to interpersonal functioning (Criterion A), operationalized via momentary reports of mentalizing, enacted warmth and dominance, and perceptions of others' warmth and dominance. Multilevel structural equation modeling revealed that self-reported maladaptive traits predicted lower perceived and enacted warmth, higher perceived and enacted dominance, and greater variability in all these processes, with informant reports showing similar but weaker patterns. Contrary to expectations, trait pathology was unrelated to average mentalizing but predicted greater fluctuations in mentalizing across interactions. Different pathological traits were associated with distinct patterns in how moment-to-moment mentalizing related to interpersonal behavior, with some traits strengthening rather than weakening these associations. These domain-specific patterns indicate that personality pathology affects not only overall interpersonal functioning but also shows distinct coordination patterns between social cognition and behavior. Our findings illustrate how adolescent personality pathology manifests in everyday social interactions, highlighting the need for interventions that target both mean levels and variability in social processes to stabilize momentary social cognition and promote affiliation over control. (PsycInfo Database Record (c) 2026 APA, all rights reserved).