Psychometric evaluation of a measure of ADHD symptoms to capture symptoms from childhood to adulthood

Traditionally attention deficit hyperactivity disorder (ADHD) has been conceptualised as a childhood condition; however, there is growing recognition that ADHD symptoms also commonly impact adults. Research has also highlighted considerable individual differences in ADHD symptom trajectories from childhood to adulthood. To better illuminate the lifespan development of ADHD symptoms, psychometric measures of ADHD symptoms are needed that can capture symptoms reliably, validly, and comparably from childhood to adulthood in research studies. Few such measures exist; however, the items of the ADHD subscale of the Social Behavior Questionnaire (SBQ-ADHD) provide strong candidates for an existing measure that can meet this need. In this study we evaluate the psychometric properties of the self-report version of the SBQ-ADHD as administered in adulthood (ages 20 and 24) to a large normative sample. We also examine the cross-informant (parent-teacher-self- reports) and developmental (age 7-24) measurement invariance of a core SBQ-ADHD item set. Results suggest that support for the SBQ-ADHD scores as a measure of adult ADHD symptoms in terms of internal consistency reliability, gender measurement invariance, and convergent validity. Items from the core set showed evidence of non-invariance for specific ages and informants, providing insights into how ADHD symptoms may manifest and/or be perceived differently by different informants and at different ages. Overall, however, results suggest that a partial invariance measurement model using the core item set could support longitudinal/cross-informant ADHD research spanning childhood to adulthood. Taken together, our findings support the use of the SBQ-ADHD items for developmental studies of ADHD symptoms from childhood to adulthood.