AGES did not have a significant main effect or interactive effect with drug assignment on PPA measured at EOT. This may indicate that TTFSL reflects a more refined phenotype better suited for identifying genetic effects. Successful cessation depends upon (i) attaining initial abstinence, (ii) maintaining abstinence without a lapse, and (iii) if a lapse occurs, avoiding full blown relapse to pre-cessation levels of smoking (59). Cessation failure can represent a breakdown at any one of these stages, each of which could reflect different underlying causes. Patient characteristics such as psychopathology, gender, and nicotine dependence are differentially predictive with regards to explaining variance in risk of lapse in comparison to other milestones and PPA (60, 61). If genetic factors operate similarly, it is possible that the genetic variation in dopamine as indicated by the AGES might have a notably stronger effect on increasing risk of lapse in comparison to some of the other cessation milestones. A recent study showed that bupropion was specifically effective at offsetting risk of initial lapse (62). At the same time, the fact that AGES did not
