Deficit in interval timing may be a candidate endophenotype for attention-deficit hyperactivity disorder

Abstract

Introduction and objective: Limited attention capacity may be the underlying mechanism for deficit in interval timing in ADHD. We tested whether attention capacity related to the time reproduction and temporal processing without motor processing can be an endophenotypes of ADHD. Methods: We assessed 223 patients with ADHD, 112 unaffected siblings, and 84 unaffected controls (ages 8–17) by using the time estimation task and the time reproduction tasks (single and dual tasks) at 5-, 12-, and 17-s intervals. Gender, age, IQ and comorbidities were controlled in data analysis. Results: Patients with ADHD were less precise in all tasks except for 5 s in the time reproduction single task. Unaffected siblings performed at the intermediate between the other two groups in the time reproduction dual tasks and time estimation tasks. Increased group difference was associated with increased time intervals. Discussions: Although unaffected siblings only showed subtle impairment on dual tasks, their performance was at the intermediate position in other tasks. Conclusion: Findings suggest that inadequate attention capacity measured by the time reproduction paradigm with dual tasks may be an endophenotype of ADHD.