The genetic architecture of ADHD is not currently clear. A polygenic transmission model seems likely (Faraone and Doyle 2001; Morrison and Stewart 1974), although some authors have suggested more dominant gene effects (Acosta et al. 2004; Deutsch et al. 1990; Maher et al. 1999; Morrison and Stewart 1974). Since it is also known that environmental factors play a role in ADHD etiology (for review see Banerjee et al. 2007), the disorder seems best described as being of multifactorial origin.
