Title: Personality pathology limits functional improvement during pharmacological treatment of adult ADHD; Personality pathology and ADHD outcomes

Attention-deficit/hyperactivity disorder (ADHD) in adults involves inattention, hyperactivity, and impulsivity, often accompanied by emotional dysregulation and significant functional impairment. Although stimulant medication effectively reduces core symptoms, its impact on broader psychosocial functioning is less consistent. Personality pathology, varying in severity and expression, may account for this variability.This naturalistic study examined how dimensional models of personality pathology influence symptomatic and functional outcomes during pharmacological treatment for adult ADHD. A total of 246 adults (66% women; mean age = 33.5 years) completed assessments of general personality dysfunction, maladaptive personality traits, ADHD symptoms, and functional impairment.Linear mixed-effects models showed that individuals with higher levels of personality dysfunction and maladaptive traits were more functionally impaired and demonstrated less symptomatic improvement during treatment. General personality dysfunction predicted greater functional impairment and higher ADHD symptom burden, while maladaptive domains - particularly Negative Affectivity, Detachment, and Psychoticism - were strongly linked to functional impairment. In contrast, Disinhibition was the only domain meaningfully related to ADHD symptom burden, consistent with its overlap with core ADHD features. Stimulant dosage and treatment duration showed only modest associations with functional change.These findings indicate that personality pathology substantially constrains the effectiveness of pharmacological treatment in adults with ADHD. Higher impairment and limited functional gains among individuals with pronounced personality dysfunction suggest that medication alone is insufficient to improve adaptive functioning. Integrated, personality-informed interventions addressing both neurocognitive and personality-based mechanisms may therefore be required to achieve lasting recovery in everyday life.Keywords: ADHD; Adult ADHD; Pharmacotherapy; Stimulant Medication; Dimensional Personality Pathology; Personality Dysfunction; Functional Impairment