be reliable, so as to reduce “noise.” Subjective responses to alcohol, measured in an experimental twin study, had a heritability estimate of 60% (Viken et al., 2003). This study used a 22-item measure called Sensation Scale (Maisto et al., 1980), which included items such as drowsy, light headed, and dizzy. Similar estimates, ranging between 0.4 and 0.6, were obtained in an Australian twin study in which subjective response to alcohol was measured across levels of BAC by a single item, namely “how drunk to you feel now” (Heath & Martin, 1991). A more recent laboratory study of the offspring of fathers who completed an alcohol challenge 20 years earlier revealed a significant positive parent-offspring association for subjective feelings of intoxication and body sway, among family history positive individuals (Schuckit et al., 2005). Although not providing direct evidence of heritability, this study is consistent with prior reports of the genetic influences on these endophenotypes and provides support for its reliability. A recent experimental twin study has also shown that subjective responses to nicotine in the laboratory are substantially heritable (Ray et al., 2007b), yet further work establishing the heritability of certain facets of subjective responses to alcohol are certainly warranted.
