Personality characteristics of ADHD adults assessed with the Millon Clinical Multiaxial Inventory-II: evidence of four distinct subtypes

This study compared the personality characteristics of 104 adults diagnosed with attention deficit hyperactivity disorder (ADHD). Personality features were assessed with the MCMI-II (Millon, 1987). Participants were divided into 4 groups based on the presence of persisting oppositional defiant disorder (ODD) or other comorbid diagnoses (ADHD only, ADHD-comorbid, ADHD-ODD, ADHD-ODD-comorbid). Significant differences between these groups were present for 9 of the 13 MCMI-II personality scales, resulting in 4 modal personality styles. ADHD-only adults evidenced mild histrionic traits, whereas the ADHD-comorbid group was more often avoidant and dependent in personality style. ADHD-ODD adults showed histrionic, narcissistic, aggressive-sadistic, and negativistic traits whereas the ADHD-ODD-comorbid group had a combination of avoidant, narcissistic, antisocial, aggressive-sadistic, negativistic, and self-defeating personality features. Implications for treatment are discussed.