Comparability of an ADHD Latent Trait Between Groups: Disentangling True Between

Objective: The aim of this study is to investigate measurement invariance (MI) for an ADHD latent trait across different sociodemographic groups (sex, age, and maternal education), IQs, and co-occurring psychiatric diagnoses. Method: Participants were 2,299 children aged 6 to 14 years. ADHD symptoms were assessed by parent report using the Development and Well-Being Assessment (DAWBA). MI was tested through multigroup confirmatory factor analysis and multiple indicators multiple causes models. Results: In a bifactor model including a general ADHD factor and three specific factors (hyperactivity, inattention, and impulsivity), invariance properties were demonstrated and no individual items showed differential functioning. The ADHD general factor was higher in boys and in those with psychiatric disorders. Younger age predicted hyperactivity. Lower IQ and higher level of education of the mother predicted inattention. Conclusion: The ADHD trait, as measured by the DAWBA, functions in the same way, and with equivalent scale, revealing true differences in ADHD symptoms based on those