Among smokers, approximately 45% of the variance in nicotine withdrawal can be accounted for by genetic factors (Pergadia et al., 2006a). Controlling for both cigarette experimentation and for quantity smoked during heaviest period of use, there are residual genetic influences on nicotine withdrawal (up to 23% of total variance; Pergadia et al., 2006a). These findings suggest that there may be genetic variance in nicotine withdrawal that is independent of genetic influences contributing to the development of tolerance to nicotine (Saccone et al., 2007a) and to experimentation with cigarettes. Even after controlling for early social factors, such as cigarette experimentation with a co-twin, previous research suggest that substantial genetic influences on nicotine withdrawal remain that cannot be attributable to twin social environmental influences (Pergadia et al., 2006b).
