studies using additional phenotypes and designs, like the age of onset of ADHD symptoms (Lasky-Su et al. 2008a), conduct problems (Anney et al. 2008b), and even a genome-wide gene–environment interaction (G × E) study evaluating genetic variants moderating the effects of maternal expressed emotion on ADHD symptoms (and conduct problems; Sonuga-Barke et al. 2008). In the following paragraphs, we will discuss most of these studies and their most important findings. The two studies exploring conduct problems in the GAIN/IMAGE dataset (Anney et al. 2008b; Sonuga-Barke et al. 2008) are beyond the scope of this review.
