Prevalence and Clinical Impact of Attention Deficit Hyperactivity Disorder in Patients With Severe Borderline Personality Disorder

Objective This study aims to estimate the prevalence and assess the clinical impact of ADHD in patients with severe borderline personality disorder (BPD) treated in a specialized unit. Methods Cross-sectional study of a sample of 145 patients diagnosed with BPD according to DSM-5 criteria, consecutively referred by outpatient psychiatrists to a Personality Disorders Unit. ADHD symptoms were assessed using the self-reported long version of the Conners Adult ADHD Rating Scale (CAARS-S:L). Groups were compared based on ADHD presence. Hypothesis testing was performed and variables with statistically significant differences were further analyzed using linear correlation and simple linear regression analyses. Results Of the 145 BPD patients, 88 (60.7%) scored above 70 on the CAARS S:L. The BPD-ADHD group showed significantly greater anxiety, depression, impulsivity, poorer global functioning, and more severe BPD symptoms. Among ADHD domains, inattention is the one that best predicts the clinical severity of BPD. Conclusions The coexistence of BPD and ADHD is associated with greater clinical severity and poorer overall functioning. Inattention, in particular, emerges as a key factor explaining BPD symptom variability. Relevance to Clinical Practice These findings emphasize the importance of systematically screening for ADHD symptoms in patients with severe BPD. Recognizing and addressing this comorbidity may allow clinicians to design more comprehensive treatment strategies, reduce clinical severity, and improve functional outcomes.