We examined performance differences between unaffected relatives of individuals with ADHD and unaffected controls, with differences pointing toward potential shared genetic liability for ADHD.   Findings revealed unaffected relatives performend significantly worse than controls in multiple domains, including working memory, processing speed, response time variability, temporal processing, and cognitive flexibility.  The full work can be found here:

de la Paz, L., Whitney, B. M., Weires, E. M., & Nikolas, M. A. (2025). A meta-analytic evaluation of cognitive
endophenotypes for attention-deficit/hyperactivity disorder: Comparisons of unaffected relatives and
controls. Journal of Psychopathology and Clinical Science. Advance online publication. https://dx.doi.org/
10.1037/abn0000985