An intensive time-series investigation of day-to-day relations between attention-deficit/hyperactivity disorder and internalizing symptoms in college students.

Young adults with attention-deficit/hyperactivity disorder (ADHD), relative to their neurotypical peers, are at increased risk for developing depression and anxiety (i.e., internalizing disorders), which may be exacerbated by the demands of adjusting to college. Longitudinal day-to-day relations between ADHD and internalizing symptoms remain poorly understood, despite their potential for highlighting pathways and mechanisms underlying comorbidity and specifying targets for microlevel assessments and interventions. The current study attempted to clarify such relations using ecological momentary assessment data collected across 28 days (once per day). Participants were 151 college students (Mage = 19.9 years, 78.8% women, 31.8% White), oversampled for ADHD-related concerns, who completed abbreviated daily measures of ADHD, generalized anxiety disorder (GAD), and major depressive disorder (MDD). Temporal results suggested increases in ADHD-related Difficulty unwinding and relaxing and Put things off until the last minute predicted increases in next-day GAD symptoms and vice versa. Increases in ADHD-related Difficulty concentrating predicted increases in next-day MDD symptoms, and increases in MDD symptoms predicted increases in ADHD-related Depend on others to keep your life in order. Contemporaneous results suggested Difficulty unwinding and relaxing, Difficulty concentrating, and Put things off until the last minute demonstrated the strongest positive relations with same-day MDD and GAD symptoms. Between-person results indicated Difficulty unwinding and relaxing and Often leave your seat were positively related to GAD and MDD symptoms. Findings highlighted ADHD symptoms that may serve as key assessment and intervention targets to prevent cycles of worsening ADHD and internalizing disorders. (PsycInfo Database Record (c) 2026 APA, all rights reserved).