Uebel, H., Albrecht, B., Asherson, P., Börger, N. A., Butler, L., Chen, W., Christiansen, H., Heise, A., Kuntsi, J., Schäfer, U., Andreou, P., Manor, I., Marco, R., Miranda, A., Mulligan, A., Oades, R. D., van der Meere, J., Faraone, S. V., Rothenberger, A., & Banaschewski, T.
Performance variability, impulsivity errors and the impact of incentives as gender- independent endophenotypes for ADHD. Journal of Child Psychology and Psychiatry, 51, 210-218 (2010) doi:10.1111/j.1469-7610.2009.02139.x.[View whole article] .[Request a copy]
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Objectives: Attention-deficit hyperactivity disorder (ADHD) is one of the most common and highly heritable child psychiatric disorders. There is strong evidence that children with ADHD show slower and more variable responses in tasks such as the Go/no-go task, tapping aspects of executive functions like sustained attention and response control which may be modulated by motivational factors and/or state-regulation processes.

The aims of this study were (1) to determine if these executive functions may constitute an endophenotype for ADHD; (2) to investigate for the first time whether known modulators of these executive functions may also be familial; and (3) to explore whether gender has an impact on these measures.

Methods: 205 children with ADHD combined type, 173 non-affected biological siblings and 53 controls with no known family history of ADHD were examined using a Go/no-go task in the framework of a multi-centre study. Performance-measures and modulating effects of event-rate and incentives were examined. Shared familial effects on these measures were assessed, and the influence of gender was tested.

Results:
1 - Children with ADHD responded more slowly and variably than non-affected siblings or controls.

2 - Non-affected siblings showed intermediate scores for reaction-time variability, false alarms and omission errors under fast and slow event-rates

3 - A slower event-rate did not lead to reduced performance specific to ADHD.

4 - In the incentive condition, mean reaction-times speeded up and became less variable only in children with ADHD and their nonaffected siblings, while accuracy was improved in all groups.

5 - Males responded faster, but also committed more false alarms. There were no interactions of group by gender.

Discussion: 1/ Reaction-time variability and accuracy parameters could be useful neuropsychological endophenotypes for ADHD. 2/ Performance-modulating effects of incentives suggested a familially driven motivational dysfunction which may play an important role in etiologic pathways and treatment approaches for ADHD. 3/ The effects of gender were independent of familial effects or ADHD-status, which in turn suggests that the proposed endophenotypes are independent of gender.