To Örebro University

The aim of this thesis is to examine objective laboratory measures of Attention Deficit Hyperactivity Disorder (ADHD) in adult persons and to develop measures for diagnosis and treatment using a psychometric instrument called the Quantified Behavior Test Plus. The instrument objectively quantifies cardinal symptom manifestations in adult ADHD using motion tracking devices and continuous performance testing.

Paper I-IV suggest that ADHD predisposes adult persons to perform poorer on continuous performance tasks and to have higher levels of motor activity while performing these tasks as compared to other clinical as well as non-clinical groups. Performance by adults with ADHD is normalized following stimulant treatment which implicates therapeutic effects and measures of response to treatment and remission for ADHD is suggested.

Paper I concludes that the psychometric instrument needs to be calibrated with regard to adult ADHD and emphasizes the importance of a composite measure for the disorder.

Paper II generates two new measures, the Weighed Core Symptom scale (WCS) - a composite measure of adult ADHD ranging from 0 to 100, and Prediction of ADHD (PADHD) - a categorical variable of the diagnostic status with good predictive power. A majority of participants with ADHD has low points on WCS (indicating high levels of symptoms) and a majority of non-ADHD normative participants has high points on WCS (indicating low levels of symptoms).

Paper III examines WCS and PADHD among complex clinical groups with shared symptoms vis-à-vis ADHD. Here, findings from Paper II are replicated since participants with ADHD present the highest level of global symptoms, followed by participants with bipolar II disorder and borderline personality disorder, participant with disconfirmed ADHD and finally, non-clinical participants has the lowest level of global symptoms.

In Paper IV, the measures are proposed as indications of response to treatment and remission after titration with stimulant treatment and WCS indicates response to small changes in dose level.

The major findings of the present thesis may be summarized as the construction of two new objective measures for ADHD in adult persons with practical implications for diagnosis and treatment. Hyperactivity is the most specific marker of ADHD in both men and women, followed by the cognitive markers of inattention and impulsivity. The composite measure, WCS, quantifies the global amount of ADHD symptoms and provides the most sensitive measure for the disorder. PADHD and WCS may not replace a thorough neuropsychiatric assessment and further studies promoting diagnostic subtype stratification is suggested. Future studies may want to consider these measures in outcome-based investigations of treatment efficacy as well as in the study of neuropsychological endophenotypes. Practical implications include clinical strategies to enhance objectivity during assessment as well as optimizing beneficial effects of treatment and attaining remission.