Objective: This study examined the bifactor models of ADHD in three groups: adolescents from the general community (n = 214), adults from the general community (n = 366), and a clinic sample (n = 245). Method: For the adolescent sample, mothers provided ratings of the ADHD symptoms, and their teachers provided ratings for Emotional Symptoms, Conduct Problems, Hyperactivity, Peer Problems, and Prosocial Behavior. For the adult sample, all adults completed self-ratings of the ADHD symptoms and measures for depression, anxiety, and stress. For the clinic-referred sample, mothers provided ratings of the ADHD symptoms, and they were diagnosed for ADHD, Conduct Disorder/Oppositional Defiant Disorder, anxiety disorders, and depression disorders. Results: The findings for all samples supported the bifactor model, and there were differences in the way the general and specific factors correlated with the external variables. Conclusion: The findings support the validity of the bifactor model. (J. of Att. Dis. 2013; XX(X) 1-XX).
OBJECTIVE: ADHD and Hyperkinetic Disorder (HKD) have the same 18 symptoms, covering inattention (IA), hyperactivity (HYP), and impulsivity (IMP). This study was aimed at providing descriptive scores for the different symptom groups in these disorders and how these scores varied by age and gender, the percentages of individuals meeting the symptom thresholds for the different ADHD types and HKD, the factor structure, and gender invariance of these symptoms in adults. METHOD: To accomplish this, 852 adults provided self-ratings for a scale comprising the 18 ADHD/HKD symptoms. RESULTS: The findings showed that age and gender had minimal effects on the ADHD symptoms. Also, in terms of symptom counts, 2% had HKD and 6.3% had ADHD (inattentive = 1.6%, hyperactive-impulsive = 2.7%, and combined type = 2.0%). Confirmatory factor analysis (CFA) provided most support for the three-factor HKD model, involving separate factors for the IA, HYP, and IMP symptoms. This model showed full measurement invariance across gender. CONCLUSION: The theoretical and clinical implications of the findings are discussed.