Applications of the bifactor S-1 model to adult ADHD symptoms: evaluating the role of hyperactivity/impulsivity and associations with emotional regulation

Abstract The structure of Attention-Deficit/Hyperactivity Disorder (ADHD) in adults has been the subject of recent research. The primary goal of the study was to examine the S-1 bifactor model, with impulsivity (IM) symptoms as the reference indicator for the general factor, and the relevance of hyperactivity symptoms (HY) for ADHD in an adult community sample. A total of 539 adults (males = 143, females = 393), aged between 18 and 65 years, completed the Current Symptom Scale and the Difficulties in Emotional Regulation Strategies-36. The S-1 bi-factor model showed good global fit, with the general factor (indexed by IM symptoms) and the inattention-specific factors (IA; indexed by the inattention symptoms) showing a clear structure and sufficient reliability. The HY factor (indexed by the HY symptoms) did not. Additionally, the general factor and the IA-specific factor were significantly associated with emotion dysregulation (ED), whereas the HY-specific factor was not. These findings support the external validity of the general ADHD-impulsivity reference factor and the IA factor, but not the HY factor, thereby questioning the clinical utility of HY symptoms in adult ADHD. Furthermore, an extended ADHD S-1 bifactor CFA model, with IM as the reference indicators for the general factor and specific factors for IA, HY, and ED, showed that the ED indicators had relatively low (though significant) loadings on the general factor and relatively high loadings on the ED-specific factor. These results suggest that ED is better conceptualized as an associated feature, rather than a core feature, of ADHD.