“…The term endophenotypes was first coined ~50 years ago to explain insects’ evolution (John & Lewis, 1966) and introduced to psychiatry by Gottesman and Shields in 1967. In complex neuropsychiatric conditions such as ADHD, endophenotypes might be defined as neuropsychological, behavioral, cognitive, or neuroanatomical quantitative “measurable components” associated/correlated with the disorder (Castellanos & Tannock, 2002; Miller & Rockstroh, 2016; Walters & Owen, 2007) that occurs at a higher frequency in individuals with the disease than in the general population, are heritable, state-independent (i.e., manifest in individuals whether the illness is active), tend to co-segregate with the illness within families, and lie in the causal pathway between gene and disease (Flint & Munafo, 2007; Lee Gregory, Burton, Shapiro, Rowland, & Coyle, 2015; Walters & Owen, 2007). Given that endophenotypes are in general continuous variables instead of categorical traits, do not depend on the inherent difficulties of a symptoms-based clinical diagnosis, and have the ability to differentiate between potential diagnoses that present with similar symptoms (Brotman et al, 2008; Gottesman & Gould, 2003), it has been hypothesized that they are well suited to study the genetic and neurophysiological basis of psychiatric traits such as ADHD (Castellanos & Tannock, 2002; Mastronardi et al, 2016; Pineda et al, 2011; Sibley et al, 2012).…”