Abstract
The literature has suggested timing processing as a potential endophenotype for attention deficit/hyperactivity disorder (ADHD); however, whether the subjective internal clock speed presented by verbal estimation and limited attention capacity presented by time reproduction could be endophenotypes for ADHD is still unknown. We assessed 223 youths with DSM-IV ADHD (age range: 10-17 years), 105 unaffected siblings, and 84 typically developing (TD) youths using psychiatric interviews, intelligence tests, verbal estimation and time reproduction tasks (single task and simple and difficult dual tasks) at 5-second, 12-second, and 17-second intervals. We found that youths with ADHD tended to overestimate time in verbal estimation more than their unaffected siblings and TD youths, implying that fast subjective internal clock speed might be a characteristic of ADHD, rather than an endophenotype for ADHD. Youths with ADHD and their unaffected siblings were less precise in time reproduction dual tasks than TD youths. The magnitude of estimated errors in time reproduction was greater in youths with ADHD and their unaffected siblings than in TD youths, with an increased time interval at the 17-second interval and with increased task demands on both simple and difficult dual tasks versus the single task. Increased impaired time reproduction in dual tasks with increased intervals and task demands were shown in youths with ADHD and their unaffected siblings, suggesting that time reproduction deficits explained by limited attention capacity might be a useful endophenotype of ADHD.
Highlights
Attention-deficit/hyperactivity disorder (ADHD) has been recognized as an early-onset, common neuropsychiatric disorder with deficits in a wide-range of neuropsychological functions [1]
We found that ADHD probands tended to overestimate in verbal estimation more than their unaffected siblings and typically developing (TD) youths, suggesting that subjective fast internal clock speed was seen in youths with ADHD, and might be a characteristic of ADHD [5]; we found that ADHD probands and their unaffected siblings were less precise in time reproduction dual tasks in terms of absolute discrepancy errors
The current study provided new evidence implying that the limited attention capacity revealed in the time reproduction dual tasks in 5–17 seconds fulfilled some of the important criteria for a candidate endophenotype for ADHD[4] because: 1) the time reproduction task had good psychometric properties, especially for the dual task paradigm [21]; 2) time reproduction deficits related to the limited attention capacity and the defect of attention allocation were found in youths with ADHD [21]; 3) time reproduction deficits related to the limited attention capacity were noted in unaffected siblings of youths with ADHD
Summary
ParticipantsThe sample consisted of 223 youths with ADHD (males, 86.9%), 105 unaffected siblings (males, 30.5%), and 84 typically developing (TD) youths (males, 81.0%). The inclusion criteria for the unaffected sibling group included the participants who were the biological siblings of youths with ADHD, who did not have lifetime or current diagnosis of ADHD according to the DSM-IV ADHD diagnostic criteria as assessed by the Chinese K-SADS-E interview with the participants and their parents/ caregivers, who were aged 8–18, and who and whose parents provided written informed consent to the study. For those families with two or more unaffected siblings, the siblings who have the closest age to the probands would be recruited. Of the 141 biological siblings, 36 (25.5%) were diagnosed either as ADHD or sub-threshold ADHD (more than three of nine symptoms in each of the DSM-IV inattention and hyperactivity-impulsivity dimensions) and 105 who did not have lifetime and current diagnosis of ADHD were identified as unaffected siblings
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