How many suspected adult ADHD cases actually receive the diagnosis? Related factors in an assessment-seeking sample

Adult ADHD assessments have increased sharply in recent years, yet the diagnostic yield and predictors of confirmed ADHD among assessment-seeking individuals remain insufficiently understood. This study aimed to examine the sociodemographic and clinical characteristics of adults self-referred or referred by clinicians for suspected ADHD, to determine confirmation rates, factors associated with confirmation, and alternative diagnoses.

A cross-sectional study was conducted on 232 adults evaluated at a regional ADHD referral center. Assessments included semi-structured clinical interviews and standardized instruments (DIVA, SCID-5, ADHD-RS). Logistic regression was used to examine factors associated with the final clinical ADHD diagnosis.

Overall, 64.2% of individuals received an ADHD diagnosis. Compared with non-ADHD participants, those diagnosed with ADHD were more frequently referred by other healthcare professionals and displayed greater academic impairment. They also showed higher rates of mood swings and delayed sleep onset. Childhood inattention emerged as the only DIVA interview score significantly associated with an ADHD diagnosis. Among individuals without ADHD, the most frequent alternative diagnoses were anxiety disorders and depressive disorders, followed by personality disorders, substance use disorders, and bipolar disorders.

Adult ADHD emerges as a multifactorial condition shaped by clinical and functional factors. The final clinical diagnosis was most strongly associated with structured clinical tools, functional impairments (in the academic domain), emotional-regulation difficulties, and childhood inattention, whereas self-reported and more general factors were less informative. These findings underscore the importance of a developmentally informed and comprehensive assessment approach, given the high prevalence of psychiatric conditions that may mimic ADHD.